Visual FoxPro - Voss Associates

For calculating dose to an organ from internal sources, the 

"specific effective energy" of a radionuclide is BEST described 

as: 

A) the energy given off by the radionuclide per 

unit of radionuclide activity 

B) the energy absorbed per unit mass of the 

organ per unit of radionuclide activity 

C) the energy absorbed per unit mass of the 

organ per disintegration of the radionuclide 

D) the energy given off by the radionuclide per 

disintegration of the radionuclide 

E) the energy transferred to the organ per unit 

of radionuclide activity 

The correct answer is: C 

The "SEE" is used in the Medical Internal Radiation Dosimetry 

(MIRD) dose modeling technique.

What is the BEST method of disposal of dog carcasses which have 

been treated with a radionuclide with a 78-hour half life? 

A) wait 3.25 days and prepare for shipment to a 

disposal facility or incinerate 

B) wait 1.625 days and bury 

C) wait 3.25 days and bury 

D) wait 32.5 days and prepare for shipment to a 

disposal facility or incinerate 

E) wait 32.5 days and bury 

The correct answer is: D 

It is common for radioactive materials licenses to allow the 

disposal of radioactive materials after ten half-lives as "clean" 

materials. In this case, the waste is still biohazardous, so 

proper burial or incineration is indicated.

The major radiological health concern assoicated with burial of 

low level solid radioactive waste is: 

A) external radiation at the surface of the 

burial site 

B) contamination of potable water supplies 

C) airborne radioactivity resulting from 

contaminated soil 

D) release of volatile radioactive daughter 

products 

E) contamination of vegetables grown in soil at 

the site 

The correct answer is: B 

The critical exposure pathway for near-surface disposal of 

radioactive materials is through drinking water. Most of the 

regulations surrounding the burial of radioactve materials, such 

as waste classification and stabilization requirements, are 

designed to prevent contamination of potable (drinkable) water.

An adequate Radiation Safety Program is the ulitimate 

responsibility of: 

A) the owner of the licensed facility 

B) the operator of the source of radiation 

C) the Radiation Safety Officer 

D) the line supervisor 

E) the radiation worker 

The correct answer is: A 

The radioactive materials license is issued to the owner of the 

facility. It is the licensee who is responsible for all aspects 

of compliance with the license, including the implementation of a 

radiation safety program. It is the duty of the RSO to 

administer the program.

A x-ray machine is operated in a closed room for several minutes. 

After the machine is turned off, how long should the operator 

wait before entering the room? 

A) he may enter immediately 

B) 10 seconds 

C) 30 seconds 

D) 1 minute 

E) 1 hour 


When the current to the x-ray tube is turned off, the production 

of electrons stops. The principle behind x-ray production in the 

tube is bremsstrahlung of these electrons with the target 

material. When the electron production stops, so to does the 

x-ray production. There is, of course, no radioactive material 

in an x-ray machine.

The exposure rate of the turbine floor of a boiling water reactor 

plant could be expected to be decreased to less than 1% at least 

_________ after shutdown? 

A) five minutes 

B) one hour 

C) twenty-four hours 

D) thirty-six hours 

E) forty-eight hours 


A good thumb rule for decay is that after seven half-lives, 

activity is less than 1% of original activity (it is actually 

1/(7)^2, or 1/128). Since the nuclide of concern on the turbine 

floor of a BWR is N-16 (T1/2 = 7.1 sec; 6.1,7.1 MeV gammas), it 

would take only 49.7 seconds to decay to less than 1%. N-16 is 

produced from the (n,p) reaction on O-16 in the reactor coolant.

The goal and future requirement regarding high level liquid waste 

is: 

A) transformation by irradiation to shorter 

lived, less toxic materials 

B) vitrification and deep ground burial 

C) use as a heat source 

D) disposal into geological formations 

E) disposal into salt formations 


High level waste, which includes spent reactor fuel and liquid 

wastes from the solvent extraction process, requires 

stabilization and disposal in deep ground geologic repositories. 

Although vitrification technology and deep ground burial are 

practiced in other industrialized nations, the U.S. lags behind 

in implementing these methods.

Below about 0.2 MeV, the most predominant photon interaction in 

lead of significance in health physics is: 

A) Pair production 

B) Compton screening 

C) Photoelectric effect 

D) Rayleigh scattering 

E) Thompson scattering 


Photoelectric effect predominates below 200 keV, Compton effect 

between 200 keV and 5 MeV, and pair production above 5 MeV.

A Pu-Be source should be stored: 

A) in a secured area and surrounded with 

sufficient lead shielding to reduce the 

exposure rate to permissible levels 

B) in a properly posted and secured area and 

surrounded with sufficient hydrogenous 

shielding to reduce the dose equivalent rate 

to permissible levels 

C) in a safe 

D) in a locked room posted with "Caution: High 

Radiation Area" signs 

E) in a locked room posted with "Caution: 

Neutron Radiation Hazard" 


Pu-Be is a neutron producing source, so it must be shielded with 

hydrogenous material. Since Pu is special nuclear material as 

defined by the NRC, it must also be secured under 10 CFR Part 70.

How many centimeters of lead were required for a shield if seven 

half-value layers were used to shield a beam of gamma photons? 

(attenuation coefficent for lead = 0.4559 per centimeter) 

A) 1.52 cm 

B) 10.6 cm 

C) 13.2 cm 

D) 15.2 cm 

E) 30.4 cm 


Since the attenuation coefficient (u) would be equal to 

.693/HVL 

then 

1 HVL = .693/u 

= .693/(.4559/cm) 

= 1.52 cm 

and 

7 HVL = 7 x 1.52 cm 

= 10.64 cm

In the shielding equation I = Io e^-(ux), if u is larger it means 

that the shielding material for the photon energy of interest is: 

A) a more effective shield 

B) a less effective shield 

C) a material with undetermined shielding 

properties 

D) no more effective than if u was smaller 

E) none of the above 


In the equation, u represents the linear attenuation coefficient, 

which is the portion of the radiation interacting with the 

shielding material per unit thickness of the material. As this 

interacting portion grows larger, the shielding material is 

becoming more effective.

The buildup factor for a gamma source and shield geometry at a 

point outside the shield is 20. The fraction of the dose 

contributed by unscattered photons is: 

A) 0.05 

B) 0.1 

C) 0.5 

D) 0.8 

E) 0.9 


Buildup factor is defined as the ratio of all photon radiation at 

a point outside a shield to primary, unscattered photons at that 

point. It is a correction factor which is used with the linear 

attenuation coefficient when calculating for broad beam ,"poor" 

geometries. If the buildup factor is 20, the ratio is 20:1, and 

the fraction of unscattered photons is 1/20, or 0.05.

Which of the following is the MOST desirable method to provide 

radiological protection during maintenance on a highly 

contaminated component? 

A) ensure workers wear protective clothing and 

respirators 

B) always use auxiliary ventilation 

C) attempt to remove contamination prior to 

maintenance 

D) ensure workers are properly trained in 

maintenance 

E) cover any exposed skin surfaces on workers 


Source removal or reduction should always be the first 

consideration when work around hazardous materials is required.

What immediate action should be taken if skin is accidentally 

broken while working with radioactive substances? 

A) immerse the wound in tepid water 

B) wash the wound under running water 

C) apply a liberal portion of titanium dioxide 

paste 

D) scrub with a brush using heavy lather and 

tepid water 

E) wash the wound vigorously with a damp cloth 


The danger in this scenario is absorption of radioactive 

materials into the bloodstream. When deconning an open wound, a 

flushing action is required.

How are tools or equipment transferred from a contaminated area? 

A) sealed in clean plastic bags 

B) decontaminated thoroughly before being 

transferred to another contaminated area 

C) painted 

D) sealed in aluminum boxes 

E) immersed in heavy water 


Contaminated equipment is usually bagged until it can be 

decontaminated or used again in a contaminated area. If the 

equipment will be contaminated again after cleaning, it may be 

ALARA to simply store the contaminated equipment for future use.

General area dose rates should be recorded: 

A) as the dose rate at the chest 

B) as the dose rate at the waist 

C) as the dose rate at the knees 

D) as the highest dose rate between the head and 

knees 

E) as the highest dose rate between the chest 

and knees 


"General area dose rates" are usually taken to determine deep 

dose equivalent rates in a work area, and don't include shallow 

dose equivalent rates to extremities (arms below the elbow, legs 

below the knee).

Which of the following surveys should be performed on a daily 

routine basis? 

A) occupied/unoccupied work areas 

B) occupied work areas 

C) fixed contamination in unrestricted areas 

D) hot spots 

E) neutron radiation in unoccupied work areas 


From a general standpoint in radiation protection, only areas 

which are occupied need to be surveyed daily to update 

radiological status. Routine surveys are performed in unoccupied 

areas in some instances, when it is difficult to determine in 

advance if the area may need to be occupied.

A "working level" is that amount of Rn-222 daughter products 

which would result in: 

A) 1.3 E5 MeV per liter of air 

B) 1 ALI in six months 

C) 1 ALI in twelve months 

D) one third of the DAC 

E) one third of the MPC 


The definition of working level includes the daughter products 

only, and not the radon itself. One working level is also 

approximately equal to 100 pCi/L or three times the occupational 

DAC for Rn-222. The occupational limit for uranium miners is 4 

working level-months per year, which is equal to 170 working 

level-hours x four months.

The following dosimetry should be worn in mixed 

neutron/beta/gamma field: 

A) self-reading quartz fiber dosimeter and 

beta-gamma responsive TLD 

B) self-reading quartz fiber dosimeter and 

criticality dosimeter 

C) albedo TLD, self-reading quartz fiber 

dosimeter and beta-gamma responsive TLD 

D) neutron film badge and criticality dosimeter 

E) beta-gamma responsive TLD and criticality 

dosimeter 


Choice C provides typical occupational personnel monitoring 

devices for the radiations listed. Criticality dosimetry is only 

useful in accident-magnitude situations.

The basic physical methods applied to protection against external 

radiation hazards are: 

A) film badges and dosimeters 

B) protective clothing 

C) time, distance, and shielding 

D) whole body counting and bioassay 

E) G-M survey meters 


Decreasing time and increasing distance and shielding are 

fundamental principles of applied radiation protection.

When using a charcoal cartridge with a full-face air-purifying 

respiratory, the protection factor afforded for I-125 is: 

A) 0 

B) 1 

C) 50 

D) 2,000 

E) 10,000 


Under NRC licenses, unless special studies and documentation are 

performed to demonstrate an actual protection factor greater than 

1 for charcoal cartridges against radioiodine, 1 must be used.

The maximum allowable radiation level at contact of a package 

shipped in other than an exclusive use vehicle is: 

A) 1 mR/hr 

B) 2.5 mR/hr 

C) 200 mR/hr 

D) 500 mR/hr 

E) 1000 mR/hr 


For a package shipped non-exclusive use, the maximum allowable 

surface radiation level under DOT's 49 CFR Part 173 is 200 mR/hr. 

A package with a surface reading between 50 and 200 mR/hr 

requires a Radioactive Yellow III label.

The use of a Radioactive Yellow III label on a package containing 

radioactive material, shipped non-exclusive use, implies: 

A) that the radiation exposure rate from any 

point on the surface of the package does not 

exceed 0.5 mR/hr 

B) that the package contains Fissile Class II 

radioactive material and the transport index 

does not exceed 0.5 

C) that the radiation exposure rate from any 


exceed 200 mR/hr and the transport index does 

not exceed 10 

D) that the radiation exposure rate from any 


exceed 10 mR/hr and that the transport index 

does not exceed 0.5 

E) that the package contains Fissile Class II 

radioactive material for which the tranport 

index exceeds 10 


A Yellow III label is required under 49 CFR 173 if the surface 

radiation level exceeds 50 mR/hr or the level at one meter (the 

transport index) exceeds 1.0.

An agreement state is: 

A) a state which agrees to disposing its own 

radioactive waste 

B) a state which agrees to abide by federal 

regulations within its borders 

C) a state which agrees to maintain occupational 

exposures ALARA 

D) a state which asserts its willingness to 

regulate the use of radiation and radioactive 

materials within its borders 

E) a state which allows radioactive shipments to 

transverse its boundaries 


As of 1994, there are 25 agreement states and 25 non-agreement 

states. A radioactive materials licensee in an agreement state 

is licensed by the state, in a non-agreement state is licensed by 

the NRC. A power reactor licensee is always licensed by the NRC 

under 10 CFR Part 50, regardless of agreement state status.

Remediation of areas contaminated with uranium mill tailings, 

under UMTRA, includes unrestricted release criteria of: 

A) less than 200 uR/hr inside habitable 

structures and radon levels less than 0.1 

working level 

B) less than 20 uR/hr inside habitable 

structures and radon levels less than 1 

working level 

C) less than 20 uR/hr inside habitable 


working level, not to exceed 0.03 working 

level 

D) less than 200 uR/hr inside habitable 


working level, alpha contamination less than 

220 dpm/cm2 

E) less than 2 uR/hr inside habitable structures 

and radon levels which result in less than 4 

working-level months per year 


The EPA sets forth these requirements in 40 CFR 190 for 

remediation of properties contaminated with uranium mill 

tailings.

A "restricted area" is an area where an individual, if he were 

continuously present in the area, could receive a radiation dose: 

A) in excess of two millirems in any one hour or 

in excess of 100 millirems in one year 

B) in excess of two millirems in any one hour or 

in excess of 100 millirems in five 

consecutive days 

C) in excess of five millirems in any one hour 

or in excess of 100 millirems in one week 

D) in excess of two millirems in any one hour or 

in excess of 100 millirems in any one week 

E) in excess of five millirems in any one hour 

or in excess of 100 millirems in five 

consecutive days 


10 CFR Part 20 (1991) defines a restricted area as any area 

controlled by the licensee for the purpose of protection of 

personnel against radiation or radioactive materials. The 

quantitative criteria stated in the question are the upper bounds 

of an "unrestricted area".

Leak test of sealed radioactive sources should be sensitive 

enough to detect: 

A) 0.005 microcuries 

B) 0.1 microcuries 

C) 0.5 microcuries 

D) 100 dpm/100 squared cm 

E) 1000 dpm/100 squared cm 


For sealed sources of licensable quantity, the NRC requires 

semiannual leak tests with a minimum detectable activity no 

greater than .005 uCi.

In the siting of nuclear reactors, the exclusion radius refers 

to: 

A) the distance downwind from a reactor that a 

person may receive a dose of 25 rem to the 

whole body from the entire passage of the 

radioactive cloud 

B) the distance specifying the area which must 

be secured by a barbed wire fence 

C) the distance downwind from the reactor that a 

person may receive either a dose of 25 rem to 

the whole body or 300 rem to the thyroid if 

he stands there for two hours after the onset 

of the postulated accident 

D) the distance specifying the area that people 

must be excluded from 



The NRC defines exclusion radius and low population zone in 10 

CFR Part 100, "Reactor Site Criteria". The low population zone 

differs from the exclusion radius only in the exposure time, 

which for the low population zone is the entire duration of the 

passage of the radioactive cloud.

The two organzations which review and approve emergency response 

plans for commercial nuclear power plants are: 

A) EPA and NRC 

B) FEMA and EPA 

C) NCRP and EPA 

D) NRC and FEMA 

E) NRC and NCRP 


NRC reviews the licensee's emergency preparedness plan, while 

FEMA reviews that of the state and local organizations.

EPA Protective Action Guidance for members of the general public 

during the early phase of a nuclear accident includes: 

A) a whole body dose exceeding 25 rem and a 

thyroid dose exceeding 125 rem 

B) a whole body dose exceeding 75 rem and no 

limit to the thyroid 

C) a total effective dose equivalent exceeding 

1 rem and a committed dose equivalent to the 

thyroid exceeding 5 rem 

D) a whole body dose exceeding 25 rem and no 

limit to the thyroid 

E) a whole body dose exceeding 1 rem and a 

thyroid dose exceeding 25 rem 


The EPA PAGs were revised in 1991 under EPA 400, which supersedes 

EPA 520. PAGs are anticipated dose levels where protective 

action, such as sheltering or evacuation, should be considered.

Which of the following contributes MOST to exposure rates on the 

turbine floor of an operating BWR plant? 

A) Cobalt-60 

B) Cesium-137 

C) Krypton-88 

D) Nitrogen-16 

E) Iodine-131 


The BWR has primary steam in the turbine, whereas the PWR design 

does not. N-16 is produced from the (n,p)reaction on O-16, which 

is plentiful in the reactor coolant (H2O). N-16 has a 7.1 second 

half-life and emits 6.1 and 7.1 MeV gamma photons.

Secondary protective barriers in medical x-ray facilities are 

designed to protect persons from: 

A) the primary beam only 

B) leakage radiation only 

C) leakage and scattered radiation only 

D) primary beam, leakage radiation and scatter 

E) scattered radiation only 


In shielding design for medical x-ray suites, primary protective 

barriers are implemented for protection against the primary beam, 

while secondary protective barriers protect against the secondary 

sources, tube leakage and scatter. The most scattering occurs at 

the patient. Shielding design for medical x-ray facilities is 

discussed in NCRP Report No. 49.

Which of the following are distinguishing colors and symbol for 

radiation warning signs? 

A) yellow and magenta with a trifoil 

B) a yellow and magenta atom 

C) a black and yellow atom 

D) a solid yellow trifoil on black background 

E) a red and white molecule 


Under the 1991 revision to 10 CFR Part 20, yellow and black may 

also be used.

A preoperational environmental monitoring program would gather 

data for all of the following purposes EXCEPT: 

A) determining the significant pathways of 

exposure to the critical population 

B) measuring the radioactivity accidentally 

released 

C) locating areas of high background 

radioactivity 

D) determining the crops which form critical 

exposure pathways 

E) establishing mean meteorological conditions 


This is not such a tricky question. Since the facility is in a 

preoperational state, no radioactivity has been released.

In planning shielding for walls of an x-ray room that are not 

subjected to the direct beam, consideration is given to provide 

shielding for: 

A) scattered radiation from all sources and 

leakage from the x-ray tube 

B) scattered radiation from natural background 

C) scattered radiation from the patient only 

D) leakage radiation from the x-ray tube 

E) secondary scattered radiation from the walls 


NCRP Report No. 49 addresses structural shielding for medical 

x-ray facilities. Primary protective barriers protect against the 

primary beam only, while secondary protective barriers protect 

against scatter and leakage. The most scatter occurs at the 

patient.

The major engineering problem assoicated with the storage of high 

level wastes is: 

A) accidental criticality 

B) heat production 

C) theft of 239-Pu contained in the waste 

D) the high content of transuranic elements 

E) chemical corrosiveness 


High level waste, which includes spent reactor fuel, liquid waste 

from the solvent extraction process, and solids into which such 

liquids have been converted, emits significant decay heat. This 

heat can have an adverse effect on engineered and geologic 

materials.

Most operating light water nuclear power reactors limit the 

release of radioactive noble gases through the use of: 

A) absolute filters 

B) a series of activated charcoal beds 

C) delay lines or tanks 

D) freeze-out traps 

E) dilution fans 


Since radioactive noble (inert) gases are not filtrable, 

adsorbable, or absorbable, the control of these fission products 

is decay, with the subsequent filtration of particulate daughter 

products.

In a linear accelerator, the most induced radiation will be 

observed: 

A) along the beam pipe 

B) in the magnets 

C) at the beam dump 

D) at the target 

E) in the air surrounding the target 


Induced radiation in an accelerator refers to neutron activation 

products. The most neutron production in a linear accelerator is 

at the target, where spallation of target atoms results in the 

release of neutrons. When thermal energies are reached by these 

neutrons, they are captured, creating activation products.

Which of the following is in the order of MOST effective to LEAST 

effective shielding materials for gamma radiation sources? 

A) water,lead,concrete,iron 

B) water,lead,iron,concrete 

C) lead,water,iron,concrete 

D) lead,iron,concrete,water 

E) lead,iron,water,concrete 


These materials are listed in decreasing order of density. The 

probability of gamma interaction increases with the number of 

electron shells, which increases with atomic number.

Which of the following thicknesses of materials would be the best 

choice for shielding a 5 Ci preparation of P-32? 

A) 1/8 inch of lead 

B) 1/4 inch of aluminum 

C) one foot of air 

D) one inch of lucite plastic 

E) any of the above 


P-32 is a "pure beta emitter" with a 14.82 day half-life and a 

1.7 MeV Emax. It is typically used in therapeutic medical 

procedures. When shielding beta particles, low atomic number 

materials are used to reduce the probability of bremsstrahlung 

photons.

The linear attenuation coefficient of a shielding material for 

gamma photons varies depending on the density of the shielding 

material and: 

A) the mass of the shielding material 

B) the energy of the photon 

C) the photon yield 

D) the half-life of the isotope 

E) the half-life of the isotope 


The linear attenuation coefficient varies inversely with the 

incident photon energy over the typical range of photon energies 

found in applied radiation protection.

Four shields are available for shielding a point source of gamma 

radiation. There is a 0.5 inch thick sheet of aluminum, a 1 inch 

thick sheet of alumimum, a 0.5 inch thick sheet of lead, and a 

one inch thick sheet of lead. Which of these shields will result 

in the highest build-up factor at a point outside the shielded 

source? 

A) the 0.5 inch thick sheet of lead 

B) the 1 inch thick sheet of lead 

C) the 0.5 inch thick sheet of aluminum 

D) the 1 inch thick sheet of aluminum 

E) the buildup will be greatest when the source 

is unshielded 


Buildup factor typically increases with both the atomic number of 

the shielding material and the thickness of the shield. Without 

any other specific data, such as the energy of the photon(s) and 

the linear attenuation coefficients of the shielding materials, B 

is the best answer.

If a shielding material has a half-value layer of 0.5 inches and 

a buildup factor of 2, how much shielding will be required to 

reduce the exposure rate from 200 milliroentgen per hour to 50 

milliroentgen per hour? 

A) 0.5 inches 

B) 1.0 inches 

C) 1.5 inches 

D) 2.0 inches 

E) 3.0 inches 


Use the shielding equation: 

I = B Io e^-(ux) 

So 

50 = (2)(200) e^-[(.693/0.5)(x)] 

50/400 = e^-[(.693/0.5)(x)] 

ln(50/400) = -(.693/0.5)(x) 

1.5 inches = x

If the TVL of concrete for Co-60 photons is 20 cm, and the total 

photon yield is 2.5 MeV/d, the thickness of concrete required to 

reduce the exposure rate from a 1000 Ci point source to 250 mR/hr 

at 6 meters is: 

A) 45 cm 

B) 75 cm 

C) 100 cm 

D) 137 cm 

E) 250 cm 


Use the shielding formula, D = 6CEN, and the inverse square law. 

Since D = 6CEN is used, meters will be converted to feet: 

6 meters x 3.28 meters/ft = 19.685 ft 

I = Io e^-(ln10/TVL)(x) 

and 

Io = 6CEN/(19.685)^2 

= (6 x 1000 x 2.5)/387.5 

= 38.71 R/hr 

So 

.250 R/hr = 38.71 R/hr [e^-(ln10/20cm)(x)] 

.250/38.71 = e^-(ln10/20cm)(x) 

ln(.250/38.71) = -(ln10/20cm)(x) 

43.8 cm = x

The units used to express u/p (mu over rho) are: 

A) /cm 

B) gm/cm^2 

C) gm/cm^3 

D) cm^2/gm 

E) cm^3/gm 


Attenuation coefficient is represented by u in units of cm^-1. 

Density is represented by p in units of 

g cm^-3. So: 

u/p = cm^-1/(g cm^-3) 

= cm^2/g

A photon beam is reduced to 0.1 of its initial intensity by lead 

with a linear attenuation coefficient of 0.567/cm. What is the 

shielding thickness? 

A) 4.06 cm 

B) 2.30 cm 

C) 1.0 cm 

D) 0.567 cm 

E) 0.05 cm 


Use the shielding equation 

I = Io e^-(ux) 

and let Io = 1 

So 

0.1 = 1 e^-(0.567cm)(x) 

0.1 = e^-(0.567cm)(x) 

ln(0.1) = -(0.567cm)(x) 

4.06 cm = x

Air sample results from an unoccupied area show a constant 

concentration of radioactive material of 0.8 DAC. To comply with 

the requirements of 10 CFR 20, the radiation protection 

technologist must: 

A) post the area "Caution: Airborne 

Radioactivity Area" 

B) require any individual who may enter the area 

to wear a respiratory protection device 

C) take no action since the area is unoccupied 

D) post the area "Caution: Airborne 

Radioactivity Area" and "Respiratory 

Protection Required" 

E) post the area "Caution: Airborne 

Radioactivity Area" and require any 

individual who may enter the area to wear a 

respiratory protection device 


10 CFR Part 20 requires posting of an airborne radioactivity area 

at 1 DAC or when an individual could receive 12 DAC-hours during 

the hours present in one week (this would be 0.3 DAC for a forty 

hour week in the area). Since the area is unoccupied and 1 DAC 

is not exceeded, no posting is required under Part 20.

A compound which is effective to remove radioactive contamination 

from the skin, after soap and lukewarm water have been 

ineffective is: 

A) acetone 

B) diethylene-triamine-pentaacetate (DTPA) 

C) trinitro toluene (TNT) 

D) potassium permanganate (KMnO4) 

E) nitrile triacetic acid 


KMnO4 will remove the first few layers of skin, and should only 

be used under medical supervision. Titanium dioxide paste has 

the same application. DTPA is an internal chelating agent for 

plutonium and americium. A risk analysis should be performed 

relative to the radioactivity to be removed whenever using these 

types of materials.

The minimum recommended face velocity for a fume hood is: 

A) 75 cubic feet per minute 

B) 75 linear feet per minute 

C) 125 cubic feet per minute 

D) 125 linear feet per minute 

E) 250 cubic feet per minute 


This is a typical face velocity for a radiochemical fume hood, in 

accordance with industrial hygiene good practices. Face velocity 

is expressed as a mass, rather than volumetric, flow rate.

For removing radioactive contamination from the skin, your best 

choice would be: 

A) a mild soap 

B) a dilute KMnO4 solution 

C) a dilute H2SO4 solution 

D) an acetone-alcohol solution 

E) a strong caustic solution 


Soap and lukewarm water is always the first choice for removal of 

radioactive contamination from the skin.

An air sampler is run for 45 minutes at a rate of 60 liters per 

minute. Net activity of the sample is 15,000 counts per minute 

using an instrument with a 10% counting efficiency. The 

approximate airborne concentration is: 

A) 2.5 E-5 microcuries per milliliter 

B) 2.5 E-7 microcuries per milliliter 

C) 2.5 E-8 microcuries per milliliter 

D) 2.5 E-9 microcuries per milliliter 

E) 2.5 E-10 microcuries per milliliter 


Use the air activity calculation 

C = net cpm/(vol)(efficiency)(dpm/uCi) 

= 15000/(45m x 60 L/m x 1E3mL/L)(.1)(2.22E6dpm/uCi) 

= 2.5 E-8 uCi/mL

In what way can we establish whether or not an individual could 

exceed some percent of the DAC? 

A) obtain an air sample 

B) carry out a general area survey 

C) carry out a loose surface contamination 

survey 

D) carry out a bioassay procedure 

E) check area radiation monitors 


Since the DAC is the Derived Air Concentration, comparison of 

exposures to any limits with DAC as the unit requires air 

sampling.

A fixed air filter at a nuclear power reactor monitored by a GM 

detector shows a SUDDEN increase in activity, then levels off at 

the higher activity. This is probably due to: 

A) an increase in radon/thoron concentrations 

B) the release of a short half-life beta emitter 

at a constant rate 

C) the release of Kr-88 or Xe-138 from the 

reactor for a short period 

D) a puff release of a short-lived beta-gamma 

emitter 



This question describes a continuous air monitor. Radon/thoron 

increases would not be sudden. Brief releases of short-lived 

beta emitters, as described in C and D would rise for a period 

and then receed. A constant release of a short-lived nuclide 

would reach equilibrium on the filter, causing the reading to 

level off at the equilibrium value.

Which of the following respiratory protection devices would 

provide the greatest protection factor in an Iodine-131 

atmosphere? 

A) full-face negative pressure with combination 

cartridge 

B) SCBA in demand mode 

C) powered air-purifying respirator 

D) full-face airline respirator 

E) supplied-air half-mask 


The atmosphere supplied device of those given with the greatest 

protection factor is the full-face ailine, with a PF of 2000. 

SCBA in the demand mode only has a PF of 50. In the 

pressure-demand mode it is 10,000.

The agency which approves the design of respiratory protection 

devices is: 

A) EPA 

B) NRC 

C) NIOSH 

D) OSHA 

E) FEMA 


The National Institute of Occupational Safety and Health approves 

all respiratory protection devices used under NRC and OSHA 

regulations.

The airborne concentration for a particulate radionuclide with a 

DAC of 2 E-7 microcuries/ml is measured as 1 E-3 microcuries/ml. 

If a worker's stay time is four hours and he cannot exceed 8 

DAC-hours, what respiratory protection device should be assigned? 

A) full-face air-purifying 

B) SCBA in demand mode 

C) SCBA in pressure-demand mode 

D) postive-pressure air-purifying 

E) atmosphere-supplied hood 


The PF must be calculated, then the device selected. Use the 

DAC-hour calculation to arrive at the PF: 

[(Concentration/DAC)/PF] x time(hrs) = DAC-hours 

[(1E-3/2E-7)/PF] x 4 hrs 

= 8 DAC-hours 

(1E-3/2E-7)/PF = 2 

(1E-3/2E-7)/2 

= PF 

2500 = PF 

The only device with a PF of 2500 or greater is the SCBA in 

pressure-demand mode, with a PF of 10,000. PFs appear in 10 CFR 

Part 20, Appendix A.

A respirator containing a high efficiency particulate filter 

offers adequate protection for all of the following EXCEPT: 

A) radon and thoron daughters 

B) xenon and krypton daughters 

C) radon and iodine 

D) uranium dust 

E) nuisance dusts 


These are the only gases that appear as choices. Daughters of 

Rn, thoron, Xe, and Kr are particulates.

Leak testing of sealed radioactive sources used for radiography 

should be performed: 

A) prior to use of the device 

B) prior to and following transportation of the 

device 

C) prior to and following transportation of the 

device and prior to the use of the device 

D) every six months 

E) annually and prior to use of the device 


These requirements appear with other industrial radiography 

regulations in 10 CFR Part 34. The contamination survey required 

prior to and following transportation of the device is required 

as part of the transportation regulations, and is not a leak test 

of the integrity of the sealed source itself.

The maximum allowable radiation level at one meter from the 

surface of a package shipped in other than an exclusive use 

vehicle is: 

A) 1 mrem/hr 

B) 2.5 mrem/hr 

C) 10 mrem/hr 

D) 100 mrem/hr 

E) 200 mrem/hr 


The maximum allowable Transport Index for a package shipped 

non-exclusive use is 10.0, which represents 10 mrem/hr at one 

meter.

When transporting a Highway Route Controlled Quantity of 

radioactive material outside of the licensee's state, 

notification must be made to: 

A) affected state governors and EPA 

B) affected state governors or their designated 

deputies and the regional DOT offices 

C) regional NRC and DOT offices 

D) regional NRC offices, DOT offices, and the 

EPA 

E) affected state governors and the NRC 


A Highway Route Controlled Quantity is a Type B quantity of 

radioactive material which is 3000 times the applicable "A" value 

or 27,000 curies, whichever is less. The advance notification 

requirements are specified in 10 CFR 71 and 49 CFR 173.

At what level does loose alpha contamination become unacceptable 

on a radioactive materials package to be shipped in a 

non-exclusive use conveyance? 

A) 10 E-5 microcuries/cm^2 

B) 10 E-5 microcuries/100 cm^2 

C) 10 E-6 microcuries/cm^2 

D) 22 dpm/cm^2 

E) 220 dpm/cm^2 


These limits appear in 49 CFR 173. The limit for beta-gamma 

contamination is ten times the limit for alpha contamination. 

For a non-exclusive use shipment, that limit would be 10 E-5 

uCi/cm^2. These limits are also frequently expressed in units of 

dpm/cm^2.

NCRP recommendations relative to radiation exposure of pregnant 

women include: 

A) dose to the fetus during the first trimester 

should be less than 0.5 rem 

B) dose to the fetus during the entire term of 

gestation should be less than 0.5 rem 

C) pregnant women should be granted a three 

month leave of absence during the first 

trimester 

D) quarterly doses for pregnant women should not 

exceed 25% of the federal quarterly dose 

limit 

E) all women of childbearing age should be 

considered pregnant and have their dose 

limits appropriately lowered 


These recommendations appear in NCRP Report No. 116 (1993). The 

fetus is most susceptible to radiation during the first trimester 

of gestation. Current regulations leave the decision of exposure 

limitation to the pregnant radiation worker.

According to the BEIR V Report, the number of additional cancer 

mortalities in a population of 100,000 people exposed to 10 rad 

of low-LET radiation would be: 

A) 800 

B) 100 

C) 50 

D) 30 

E) 10 


The 1990 BEIR V Report increased the estimates of cancer 

mortalities fro low-LET radiation by a factor of about 8:3 over 

its 1980 BEIR III estimates. The increase was largely due to 

more complete data regarding neutron and gamma dose contribution 

to the atomic bomb blast survivors.

The NRC's annual limit for the sum of the deep dose equivalent 

and the committed dose equivalent is: 

A) 50 rem 

B) 15 rem 

C) 10 rem 

D) 5 rem 

E) 2 rem 


The limit described is referred to as the Total Organ Dose 

Equivalent (TODE). Based upon 1977 ICRP recommendations, the 

annual TODE limit for all organs and tissues except the lens of 

the eye is 50 rem. The annual limit for the lens under NRC 

regulations is 15 rem.

Allowable radiation and contamination levels on protective 

clothing are established primarily by: 

A) the NRC 

B) the NCRP 

C) the state licensing body 

D) the licensee 

E) the ICRP 


This is a good example of administrative levels imposed by a 

facility to ensure that regulatory limits are not exceeded.

An accidental criticality incident subjects a number of people to 

suspected high neutron exposures. If none of the people were 

wearing personnel dosimetry, how would you rapidly screen them to 

determine which individuals received high exposures? 

A) send them to the medical department for a 

blood count 

B) place a GM detector on the abdomen and look 

for meter deflection 

C) send each person for a complete physical 

examination 

D) send the people to the hospital for bedrest 

and observe them for radiation sickness 

E) collect samples for urinalysis 


The abdomen or armpit represent large blood pools that can be 

effective indicators of accident-scale neutron exposures. The 

Na-23(n,gamma)Na-24 reaction produces a response in a G-M 

detector, with a reading of 1 mrad/hr on the instrument 

representing an acute neutron dose equivalent of 500 rem.

The four emergency classifications of an accident at a nuclear 

power plant, in ascending order of severity, are: 

A) Unusual Event, Alert, Site Area Emergency, 

General Emergency 

B) General Emergency, Site Area Emergency, 

Alert, Unusual Event 

C) General Emergency, Alert, Site Area 

Emergency, Unusual Event 

D) General Emergency, Unusual Event, Site Area 

Emergency, Alert 

E) Alert, Site Area Emergency, General 

Emergency, Unusual Event 


Each level of emergency classification is declared based upon the 

fraction of the EPA Protective Action Guides (PAGs) reached at 

the site boundary, or whether the PAGs will be exceeded offsite.

Under EPA 520, a one year old child's thyroid was used as the 

critical organ for off-site doses of I-131, primarily because: 

A) of differences in effective energy term 

B) of differences in retention 

C) of differences in uptake 

D) of its smaller mass (by a factor of 10) 

compared to that of an adult 

E) of the greater milk consumption of a child as 

compared to the consumption of an adult 


The child thyroid, as of 1994, is no longer used as part of the 

Protective Action Guides from EPA 400. Under EPA 520, it had 

been used because, for a unit intake of radioiodine, the dose 

would be greater for an organ of less mass. That is, since dose 

is measured in ergs/gm, decreasing the number of grams for the 

same number of ergs means a higher dose.

A technician responds with emergency medical personnel to a 

contaminated injured man. What is his first priority? 

A) assisting with the decontamination of the 

wound 

B) informing medical personnel of radiological 

conditions 

C) medical treatment of the patient 

D) evacuation of the patient 

E) movement of the patient to a low background 

area 


Since medical personnel are already present, the duty of the 

technician is to provide radiological coverage for the response 

operation. If medical personnel were not present, the condition 

of the patient would be the technician's first priority.

The major off-site dose during the Three Mile Island accident was 

due to: 

A) Cobalt-60 

B) Xenon-133 

C) Iodine-131 

D) Iodine-125 

E) Cesium-137 


The highest dose equivalent to a member of the public as an 

immediate result of the accident was about 2 mrem. The 

radioiodines, which were originally projected to create 

significant dose off-site, reacted with NaOH in the containment 

spray and were essentially "rinsed" from containment. Krypton-85 

was another significant contributor to the dose off-site.

The amount of shielding required to reduce a 2.5 Roentgen per 

hour gamma source to 2.5 milliroentgen per hour is: 

A) six half-value layers 

B) seven half-value layers 

C) two tenth-value layers 

D) three tenth-value layers 

E) four tenth-value layers 


The transmission factor for the shielding in this problem is 

2.5mr/2.5R, which is equal to 1/1000. 

It becomes clear that, since 1000 is an exponential of 10, TVLs 

will appear in the answer. So use 

I = Io (1/10)^n 

then 

2.5 = 2500 (1/10)^n 

2.5/2500 = (1/10)^n 

log(2.5/2500) = n x log(1/10) 

3 = n

A 500 millicurie Phosphorous-32 solution has spilled in a 

hospital room. A quick method of shielding the spill and 

preventing the spread of contamination would be: 

A) open the window to completely ventilate the 

room 

B) increase the building ventilation flow to 

dilute the solution throughout the building 

C) use a broom to consolidate the spill and 

cover with towels 

D) cover the spill with a plastic bedsheet 

E) hose down the room and direct the spill to 

the floor drain system 


Choices C and D are the only choices which include a shielding 

consideration. Since P-32 is a 1.7 MeV Emax "pure beta-emitter", 

plastic is an appropriate shield. 

A broom should never be used to perform surface decontamination 

due to the potential for airborne radioactivity.

The transport index is determined at: 

A) contact 

B) one foot 

C) three feet 

D) one meter 

E) two meter 


The Transport Index is the dimensionless number which represents 

the number of mrem at one meter from the surface of a radioactive 

materials package to be transported. It is always expressed to 

one place to the right of the decimal point.

The basic physical controls applied to protection against 

internal radiation hazards are: 

A) film badges, dosimeters, ion chambers, survey 

meters 

B) ventilation, air cleaning equipment, 

respirators 

C) time, distance, shielding 

D) standards, regulations, procedures 

E) bioassay, whole body counting, nose wipes 


The engineering controls (ventilation, filtration) should always 

be considered prior to the use of respiratory protection 

equipment.

The BEST shielding for a Phosphorus-32 source would be: 

A) lead 

B) copper 

C) tin 

D) polyethylene 

E) iron 


Since P-32 is a 1.7 Emax "pure beta-emitter", a low-Z material 

should be used as shielding so that bremsstrahlung is prevented. 

P-32 is typically used in therapeutic nuclear medicine, and has a 

half-life of 14.28 days.

Federal regulations governing licensing and radiation safety for 

industrial radiographic operations can be found in: 

A) 10 CFR 20 

B) 10 CFR 25 

C) 10 CFR 30 

D) 10 CFR 34 

E) 10 CFR 35 


Industrial radiographic operations also are subject to the 

requirements of 10 CFR Part 20, "Standards for Protection Against 

Radiation".

As a result of Three Mile Island accident, the USNRC requires 

nuclear power plants to install noble gas and containment 

raidation monitors in the following detection ranges: 

A) 1 E2 microcuries/cc to 1 E8 microcuries/cc 

for noble gas and 1 to 8 R/hr for radiation 

B) up to 1 E5 microcuries/cc for noble gas and 1 

to 8 R/hr for radiation 

C) up to 1 E5 microcuries/cc for noble gas and 1 

to 1 E8 R/hr for radiation 

D) up to 1 E2 microcuries/cc for noble gas and 1 


E) up to 1 E2 microcuries/cc for noble gas and 1 



These requirements were implemented following the accident, 

because operators interpreted offscale raedings to be 

instrumentation malfunction.

Suggested sizes of the plume exposure and ingestion pathway 

emergency planning zones, respectively, are: 

A) 1 mile and 3 miles 

B) 5 miles and 15 miles 

C) 10 miles and 50 miles 

D) 15 miles and 60 miles 

E) 20 miles and 100 miles 


NRC's NUREG 0654 on emergency planning guidance for nuclear power 

plants sets forth these recommendations. They are based on an 

external critical exposure inside a ten mile radius and an 

internal critical exposure pathway outside of a ten mile radius.

Radioactive material may be transported through the U.S. Postal 

Service provided that: 

A) the surface radiation level on the package 

does not exceed 0.5 millirem per hour 

B) the surface radiation level on the package 

does not exceed 50 millirem per hour 

C) the surface radiation level on the package 

does not exceed 200 millirem per hour 

D) the transport index on the package does not 

exceed 1.0 

E) the transport index on the package does not 

exceed 10 


The USPS limits packages to "Limited Quantities" of radioactive 

material. The 0.5 mrem/hr surface limit is one of the criteria 

for a Limited Quantity.

When leak testing an industrial radiography source, the 

contamination sample should be obtained: 

A) on the inside of the source tube 

B) inside the source housing 

C) on the surface of the sealed source 

D) on the handle of the camera housing 

E) on the source locking mechanism 


This is the best choice, since if the source is leaking 

contamination, the contamination will be distributed on the 

inside of the source tube when the source is move from the 

shielded to the unshielded position. It is not ALARA, and even 

dangerous, to directly swipe a sealed source of the activity 

required for industrial radiography sources.

What is the attenuation coefficient for a material if it takes 

10.6 centimeters of the material to reduce a 128 R/hr gamma 

source to 1 R/hr? 

A) 12.07/cm 

B) 0.4577/cm 

C) 0.083/cm 

D) 0.1356/cm 

E) 1.356/cm 


Use I = Io e ^-(ux) 

So 

1 = 128 e^-(u)(10.6 cm) 

1/128 = e^-(u)(10.6 cm) 

ln(1/128) = -(u)(10.6 cm) 

0.4577/cm = u

To use elevated release dispersion modeling during a 

design-basis accident, the release stack must be: 

A) at least five times its height from the 

reactor building 

B) at least two times its height from the 

nearest adjacent building 

C) at least two and one-half times the height of 

the nearest adjacent building 

D) at least two times the height of the reactor 

building 

E) at least two and one-half times its height 

from the nearest adjacent building 


According to NRC guidelines, the stack must also be at least one 

times its height away from the nearest adjacent buiding. If 

these criteria are not met, mixed-mode or ground release modeling 

must be used.

The MAIN purpose of isokinetic sampling in a stack is to: 

A) increase turbulent flow from insertion of the 

sampling head into the gas stream 

B) obtain the same representative fraction of 

small and large particles as in the stack gas 

C) prevent deposition of the particles in bends 

of the sample tubing 

D) collect a relatively large proportion of the 

smaller particles from the gas stream so as 

to approximate the ideal aerosol median 

aerodynamic diameter (AMAD) of 1 um 

E) maintain a constant gas temperature during 

sampling 


Isokinetic sampling is established when the mass flow rate 

(linear flow rate) is equal in the process line and the sample 

line. This is established by regualting volumetric sample flow 

in the sample line based upon the ratio of process and sample 

line diameters.

Workers will cut into a pipe where fission and activiation 

products are present six months after facility shutdown. 

Assuming respiratory protection is required, the proper device to 

select is: 

A) air-purifying half-mask with charcoal 

cartridge 

B) air-purifying full-face respirator 

C) air-purifying full-face respirator with 

charcoal cartridge 

D) self-contained breathing apparatus 

E) atmosphere-suplied full-face respirator 


The intent of this question centers on the recognition that the 

short-lived fission gases will not be present after a period of 

six months.

A toluene and P-32 spill occurs in a lab. The BEST selection for 

protective clothing and cleanup is: 

A) acid suit, rubber gloves, and absorbent 

B) plastic boots, gloves, and apron with 

faceshield and absorbent material 

C) lab coat, rubber gloves, and room ventilation 

D) airline suit, rubber boats, and room 

ventilation 

E) lab coat, rubber gloves, and dilution with 

demineralizer water 


B appears to be the best choice since it provides face,trunk, 

hand, and foot protection and specifies a cleanup medium. A 

provides no face protection (and toluene is a solvent, not an 

acid), and D is respiratory protection overkill, with no cleanup 

method specified.

In the formula I = (B) Io e^-(ux), the attenuation coefficient 

for the shielding material is represented by: 

A) x 

B) u 

C) e 

D) I 

E) B 


In this classical shielding equation, 

I = shielded radiation intensity 

Io = unshielded radiation intensity 

B = buildup factor 

u = attenuation coefficient of the shield 

x = shield thickness

The dose buildup factor is 5 at the particular shielded location. 

What percentage of the exposure rate is due to primary 

(unscattered) photons? 

A) 5% 

B) 10% 

C) 20% 

D) 80% 

E) 95% 


The buildup factor is the ratio of all photons at a point outside 

a shield to primary photons at that point. If the ratio is 5:1, 

then the primary photons comprise 1/5, or 20%, of the exposure 

rate.

Who is ultimately responsible for NRC license compliance at a 

university? 

A) RSO 

B) administration 

C) state 

D) county 

E) NRC 


Since the license is issued to the owner of the licensed 

facility, the administration of the university would probably be 

the entity responsible for compliance. The next closest answer 

is the state, but only if it were a state university. The RSO is 

only responsible for implementing the radiation safety aspects of 

the license.

What is the appropriate method of using high-Z and low-Z 

shielding materials for a mixed beta-gamma source? 

A) high-Z followed by low-Z 

B) low-Z followed by high-Z 

C) high-Z surrounded by low-Z 

D) low-Z surrounded by high-Z 

E) high-Z material only 


The low-Z material would be placed closest to the source to 

shield the beta particles, while preventing bremsstrahlung, and 

the high-Z material would follow to shield the gamma photons.

The apparent half-life of an air sample run for one-half which 

contains Rn-222 and its daughters is: 

A) 10 minutes 

B) 20 minutes 

C) 35 minutes 

D) 50 minutes 

E) 90 minutes 


This fact is useful in applied health physics to distinguish 

between long-lived alpha-emitters and radon progeny on an air 

sample. If half the activity is removed in 35 minutes, radon 

progeny is indicated.

Immediate telephone notification to the USNRC operations center 

is required when an individual receives an acute total effective 

dose equivalent of at least: 

A) 1 rem 

B) 5 rem 

C) 25 rem 

D) 150 rem 

E) 375 rem 


Under 10 CFR Part 20, immediate notification for acute radiation 

exposures is required at doses equal to five times the annual 

limits. 24-hour notification is required if acute doses are one 

time the annual limits.

The most effective ALARA program will be based on: 

A) a good radiological control supervisor 

B) worker awareness of hazards in the work place 

C) a large radiological control staff 

D) a strong management commitment to radiation 

protection 

E) the size of the work force 


Without a management commitment to ALARA, the other elements of 

an effective program cannot exist. The NRC addresses the 

importance of this commitment in Regulatory Guide 8.10, 

"Operating Philosophy for Maintaining Occupational Radiation 

Eposures As Low As Reasonably Achievable".

After shutdown of a particle accelerator, the most induced 

radiation can be observed at: 

A) the magnet assemblies 

B) the beam pipe 

C) the target and beam stop 

D) the RF generator 

E) the ion generator 


Induced radiation in an accelerator is due to neutron activation. 

The most neutron production is at the target and beam stop area, 

from the spallation of target atoms and photoneutron production 

by high energy photons.

Regarding respiratory protection, which of the following 

statements is MOST true? 

A) respirators are an effective method of 

reducing exposure to hazardous materials and 

should be utilized whenever possible 

B) respirators should never be considered if 

they may increase physical stress to the 

worker 

C) removal of hazardous materials should be 

attempted prior to considering the use of 

respriatory protection 

D) respiratory protection should only be used in 

environments which are Immediately Dangerous 

to Life and/or Health 

E) respirators are always more practical in 

hazardous environments than implementing 

engineering controls 


The use of respiratory protection equipment adds risk to the 

woker's job. To minimize risk, which is the goal of the safety 

and health specialist, use of engineering controls and source 

removal/reduction should be considered prior to the assignment of 

respiratory protection.

In a linear accelerator radiation survey, the radiation 

protection technologist should be aware of interference which may 

give erroneous readings from: 

A) skyshine 

B) magnetic fields 

C) neutrons 

D) x-rays 

E) microwaves 


Strong magnetic pulsed fields are present around an operating 

accelerator. These fields can affect electron flow in instrument 

circuitry, causing erroneous response. Skyshine, neutrons, and 

x-rays could all be real concerns in an accelerator, as could 

microwaves. Microwaves, however, would not produce a response in 

an ionizing radiation detector.

Decontaminatin of a hot cell is most easily accomplished if the 

hot cell is: 

A) constructed of styrofoam 

B) coated with water-based paint 

C) constructed of concrete 

D) constructed of stainless steel 

E) supplied with negative pressure ventilation 


Hot cells are generally closed containments used to work on 

high-contamination or high-radiation components, sometimes with 

remote handling devices. Smooth, non-porous materials are best 

for ease of decontamination.

Personnel monitoring equipment is required if an individual 

working in the area is likely to receive: 

A) 10% of the annual dose limit in any one year 

B) 25% of the annual dose limit in any one year 

C) 500 millirem in one year 

D) 5 millirem in any one hour 

E) 100 millirem in any consecutive days 


10 CFR Part 20 requires personnel monitoring devices when an 

individual is likely to exceed 10% of the annual total effective 

dose eqivalent limit.

The specific activity which represents the DOT-regulated 

radioactive material lower limit is: 

A) 0.005 microcuries 

B) 0.005 microcuries/gm 

C) 0.002 microcuries 

D) 0.002 microcuries/gm 

E) 0.02 microcuries/ml 


Choices B and D are the only values expressed in units of 

specific activity. The DOT does not subject to its regulation 

any radioactive material having a specific activity less than 

0.002 uCi/gm.

A nurse drops a 30 millicurie liquid I-131 solution at the only 

entrance to a patient's room, causing a spill. His immediate 

action should be to: 

A) acquire absorbent material at the nurses 

station 

B) evacuate the patient 

C) notify the RSO 

D) check the hall for contamination 

E) ventilate the room 


Prior to potentially becoming part of the problem, it is always a 

good practice to notify someone of the situation, your actions, 

and whether assistance is needed. Then, stop the spread of 

contamination and restrict access to the area. Since the spill 

is at the only entrance, evacuation of the patient is 

impractical.

You enter a room and are directing cleanup of a liquid spill. 

What precautions do you prescribe to prevent the spread of 

contamination? 

A) clean the edges of the spill first 

B) install shielding around the spill 

C) work rapidly to minimize the dose 

D) install ventilation to assist in the cleanup 

of the spill 

E) dilute with large volumes of water 


When cleaning up a radioactive spill, the spill should be cleaned 

from the outside in, from low contamination to high.

An air sample is run at 2 cubic feet per minute for 70 minutes. 

The sample yields 3,500 net counts per minute on a counting 

system with a 14% efficiency. The sample activity is: 

A) 1.13 E-8 micorcuries/cc 

B) 1.99 E-7 microcuries/cc 

C) 2.84 E-9 microcuries/cc 

D) 4.05 E-8 microcuries/cc 

E) 8.04 E-5 microcuries/cc 


For this problem, the conversion from cubic feet to cubic 

centimeters must be known. 

1 ft^3 = 2.832 E4 cc 

Use the air activity calculation 

C = net cpm/(vol)(efficiency)(dpm/uCi) 

= 3500/(2cfm x 70m x 2.832E4cc/cf)(.14)(2.22E6dpm/uCi) 

= 2.84 E-9 uCi/cc

In a medical hospital using radioisotopes for diagnostic and 

therapeutic purposes, what limits are placed on the discharge of 

patient excreta into the sanitary sewer system? 

A) no limit if the patient doses are less than 1 

mCi each 

B) activity totaling 1 curie per year may be 

discharged 

C) no limitation 

D) limited only by the amount of dilution water 

in the sewer to 1E-5 microcuries/cc gross 

activity 

E) total activity which may be discharged per 

quarter is 1.25 curies 


These limits are set forth in 10 CFR Part 20. As excreta, there 

is no limitation. There may be 1 curie total per year disposed 

in the sewer per facility (non-excreta), with an addtional 

allowable 5 Ci H-3 and 1 Ci C-14.

In shielding sources which produce gamma rays, the exposure rate 

outside a shield exceeds that calculated from pure exponential 

attenuation (e-^ux) PRIMARILY because of: 

A) x-rays resulting from the photoelectric 

interaction of primary photons in the shield 

B) annihilation photons being produced by the 

interaction of primary photons in the shield 

C) the contribution from Compton scattered gamma 

rays 

D) Bremsstrahlung 

E) photoelectric absorption in the shield 


Compton scattering is the greatest contributor to the buildup 

factor at a point outside the shield. Buildup factor is used to 

correct the pure exponential attenuation equation when performing 

shielding calculations.

In performing a preoperational radiological assessment for a 

nuclear facility, consideration is given to all of the following 

EXCEPT: 

A) cosmic radiation levels 

B) intake pathways to the public 

C) baseline gamma radiation levels 

D) presence of predominant radionuclides 

E) gamma radiation anomalies 


Cosmic radiation levels are fairly constant throughout the 

environment, and contribute only slightly to the total background 

radiation. All of the other distractors represent valid 

considerations.

Radioactive liquids may be transported via public highway, 

provided that: 

A) radioactive liquids may NOT be transported 

over public highway 

B) the liquid is contained within Type B 

packaging 

C) the liquid is labeled "Yellow III" and is 

contained in a DOT Spec 7A Type A packaging 

D) the package is marked "This End Up" and twice 

the amount of absorbent material required to 

absorb the liquid is in the package. 

E) the package includes a sealed glass liner and 

is marked "Fragile" 


These requirements appear in 49 CFR 173. Do not confuse 

free-standing water restrictions on radioactive wasteforms with 

transportation requirements for radioactive liquids.

The target material in an x-ray generating device is typically 

constructed of: 

A) aluminum 

B) tungsten 

C) zinc alloy 

D) lead 

E) uranium 


Tungsten has a high melting point to withstand the heat generated 

in the device, and has a high-Z to promote bremsstrahlung.

The protection factor for an atmosphere-supplied hood which is 

operated at the maximum recommended flow rate with a calibrated 

flow guage is: 

A) 10,000 

B) 2,000 

C) 1,000 

D) 50 

E) 10 


If operated at less than the recommended flow rate (which for 

most hoods is 4-6 cfm), the hood is assigned a protection factor 

of 1000. Protection factors appear in 10 CFR Part 20 Appendix A.

In a medical facility which uses Technecium-99m for diagnostic 

evaluation, the largest amount of dose is received by the 

technician while: 

A) administering the desired quantity to the 

patient 

B) calibrating the amount of material 

C) disposing of radioactive byproduct waste 

D) eluting the generator 

E) exposed to Technecium-99m daughter products 


Tc-99m is produced by the decay of Mo-99. When a quantity of 

Tc-99m is desired, the technician elutes the generator wich 

contains the Mo-99 and the Tc-99m. The Tc-99m is soluble and is 

removed in saline solution. This process is also termed "milking 

the cow".

A shield has to be constructed in front of a hot spot to reduce 

the exposure rate by 80%. The half value layer for the shielding 

is one-quarter inch. What is the minimum number of shielding 

thicknesses required? 

A) 0.5 

B) 1 

C) 2 

D) 3 

E) 4 


Since HVLs are given, use 

I = Io (1/2)^n 

So let Io = 1, and 

1 - 0.8 = 1 (1/2)^n 

0.2 = (1/2)^n 

log(0.2)= n x log(1/2) 

2.32 = n

The FDA has recommended potassium iodide as a thyroid-blocking 

agent when doses to the thyroid are anticipated to be in excess 

of: 

A) 0.5 rem 

B) 1 rem 

C) 5 rem 

D) 25 rem 

E) 75 rem 


This recommendation comes from the FDA publication, "Potassium 

Iodide as a Thyroid-Blocking Agent in a Radiation Emergency: 

Final Recommendations on Use", June, 1982.

Reactor chemistry samples are often treated with nitric acid to: 

A) remove interference from volatiles 

B) preserve the sample for future analysis 

C) destroy organics 

D) prevent cross-contamination 

E) aid isotopic separation 


The nitric acid helps metals in the sample to remain in solution 

for analysis at a later date.

Which of the following radionuclides would present the least 

hazard as fallout from a nuclear weapon detonation? 

A) Pu-235 

B) Cs-137 

C) Zr-95 

D) Sr-89/Sr-90 

E) I-131 


Pu-235 is the only non-fission product which appears as a 

response. Furthermore it is the isotope 239, not 235, which is 

present in a nuclear weapon.

When sampling for radioactive fallout, the nuclides of concern in 

cow feed, milk, grazing vegetation, and manure are: 

A) Pu-230 and Cs-137 

B) Sr-90 and Pu-239 

C) Sr-90 and Cs-137 

D) Cs-137 and Am-241 

E) Sr-90 and Am-241 


These long-lived fission products are good indicators of the 

extent of fission releases to the atmosphere. Each of these 

decay by beta, and have an affinity for cereals and grains. The 

shorter-lived fission products are less useful in the assessment 

of population dose, although their contribution to the dose is 

important.

A radiation user authorized under a university broad scope NRC 

license to use a 1 Ci PuBe source tells the RSO that the source 

has been removed from its storage facility and cannot be found. 

The RSO should: 

A) call the state health department for 

assistance 

B) call the governor to give warning to 

residents of the state 

C) call the NRC and advise user to follow 

emergency procedures for a lost source 

D) call the nearest RAP team for assistance 

E) convene the Radiation Safety Committee to 

decide appropriate action 


Since Pu-Be contains special nuclear material, 24-hour 

notification to the NRC is required under 10 CFR Part 70.

One DAC-hour is approximately equal to a committed effective dose 

equivalent of: 

A) 0.025 rem 

B) 0.0025 rem 

C) 0.25 rad 

D) 0.25 rem 

E) 2.5 rad 


Since the sALI is the amount of radioactive material that will 

produce 5000 mrem CEDE if taken into the body, and 2000 DAC-hrs = 

1 sALI, then 

1 DAC-hour x (1 sALI/2000 DAC-hrs) x 5000 mrem/sALI 

= 2.5 mrem = .0025 rem

Which of the following is one function of the ALARA program? 

A) train workers in methods to reduce exposure 

B) increase the number of qualified workers to 

reduce individual worker dose 

C) enable radiation workers to design shielding 

systems 

D) minimize a company's legal liability in 

accidents 

E) place total responsibility for ALARA upon the 

worker 


Regarding choice B, the risk should never be spread to a larger 

population to minimize individual dose. Regarding choice E, a 

management commitment to ALARA is the most important element of 

the ALARA program, and although it places some responsibility on 

the worker, most of the responsibility is on management.

Which of the following materials will yield the greatest amount 

of bremsstrahlung raidation when irradiated with electrons of the 

same energy and intensity? 

A) beryllium 

B) aluminum 

C) tungsten 

D) uranium 

E) lead 


The probability of bremsstrahlung increases with the atomic 

number of the material. Of the materials listed, uranium has the 

highest atomic number.

The protection factor provided by a self-contained breathing 

apparatus in the pressure-demand mode is: 

A) 10 

B) 50 

C) 1,000 

D) 10,000 

E) 20,000 


In the demand mode, the PF for SCBA is only 50. Respiratory 

protection factors appear in 10 CFR Part 20 Appendix A.

When is a neutron radiation survey usually performed? 

A) after reactor startup 

B) upon receipt of a radioactive materials 

shipment 

C) when there are suspected fuel cladding 

failures within the active fuel inside the 

reactor 

D) before an object is released from a 

controlled area 



As the reactor goes through its power ascension, neutron dose 

rates in surrounding areas will increase. If control rods are in 

a different configuration than during the previous reactor run, 

the location of the neutron fields will most likely be different.

Respiratory Protection Factors are found in: 

A) 10 CFR 20.101 

B) 10 CFR 20 Appendix A 

C) 10 CFR 20 Appendix B 

D) 10 CFR 20 Appendix C 

E) 10 CFR 19.13 


Appendix B lists Derived Air Concentrations (DACs) and Annual 

Limits on Intake (ALIs). Appendix C lists Quantities of Licensed 

Materials Requiring Labeling. 10 CFR 19 contains required 

Notices to Workers.

Why should swipes in a loose-surface contamination survey be kept 

separate from one another? 

A) to avoid mislabeling the swipes 

B) to avoid cross-contamination 

C) to avoid contaminating the plastic bag 

D) to avoid criticality 

E) to reduce radwaste volume 


Cross-contamination of these surface contamination samples will 

yield inaccurate results when counted and documented on the 

survey report.

The maximum allowable exposure rate at contact of any external 

surface of an exclusive use vehicle transporting radioactive 

materials is: 

A) 1 mR/hr 

B) 5 mR/hr 

C) 100 mR/hr 

D) 200 mR/hr 

E) 1000 mR/hr 


These apply to exclusive use shipments only. The external 

contact dose rates apply to the four sides, top, and underside of 

the vehicle. The limit in normally occupied spaces of the 

vehicle is 2 mR/hr. The limit at 2 meters from the sides of the 

vehicle is 10 mR/hr.

World population exposures due to fallout Cs-137 from nuclear 

detonations can best be estimated by collecting samples of: 

A) cereals 

B) milk 

C) fish 

D) meat 

E) water 


Cereals have the greatest affinity for cesium of the materials 

listed. Illite clay in pond and river beds is also a useful 

indicator for cesium dispersion into the environment.

Suppose a worker, over the course of a year, orally ingests 30% 

of the ALI and inhales 1,000 DAC-hours of 226-Ra. What is the 

maximum whole body external exposure this worker can receive 

without exceeding the ICRP 26 recommended limit? 

A) 0.005 Sv 

B) 0.01 Sv 

C) 0.1 Sv 

D) 0.05 Sv 

E) 0.5 


Since 1000 DAC-hours represents half of the ALI, plus 30% of the 

ALI by ingestion, the CEDE is 80% of 5 rems (0.05 Sv), or 4 rems 

(0.04 Sv). The remaining dose that the worker would be allowed 

is 

0.05 Sv - 0.04 Sv = 0.01 Sv

Strict adherence to ICRP Publication 26 would allow: 

A) plutonium internal doses to be regulated 

using annual dose equivalent rather than 

committed dose equivalent 

B) deletion of record keeping for internal doses 

less than 50% of the allowable dose limit 

C) consideration of internal and external dose 

limits separately 

D) use of air samples and stay-time calculations 

instead of respirator usage, if it is deemed 

to be ALARA 

E) the worker to choose the type of respiratory 

protection device if use is required 


ICRP 26 (1977) introduced the total dose concept, rather than 

treating internal and external exposures differently. Keeping 

the total dose ALARA, be it from external or internal sources, is 

consistent with these recommendations.

ICRP 30 replaces the ICRP 2 concept of critical organ with the 

concept of: 

A) genetic region 

B) target tissue 

C) source region 

D) organ equivalent 

E) tissue region 


The committed dose equivalent limit in a year for any individual 

target tissue under these 1977 recommendations is 50 rem. Each 

target tissue is assigned a tissue weighting factor to draw a 

proportion of the risk of stochastic effects from irradiation of 

that tissue to the total risk of stochastic effects when the body 

is irradiated uniformly. It is important to note that tissue 

weighting factors have been revised in the 1990 recommendations 

of the ICRP (ICRP 60).

ICRP recommends a weighting factor of 0.01 for assessing 

stochastic risk to skin. This means: 

A) radiogenic skin cancer is a low risk 

B) radiogenic skin cancer is a high risk 

C) spontaneous skin cancer is a low risk 

D) radiogenic skin cancer exceeds spontaneous 

skin cancer as a risk 

E) dose equivalent to the whole body is 100 

times dose to the skin 


A weighting factor of .01 indicates that the proportion of risk 

of cancer to the skin to the risk of all cancers at a given dose 

equivalent is 1 in 100. This indicates that radiation-induced 

skin cancer is a low risk compared to other radiation-induced 

cancers.

ICRP 26 recommends the use of a weighting factor to express the 

proportion of stochastic risk from an irradiated tissue, T, to 

the total risk when a body is uniformly irradiated. For the 

lung, this factor has a value of: 

A) 0.03 

B) 0.12 

C) 0.25 

D) 0.30 

E) 0.50 


The ICRP 26 (1977) tissue weighting factors are as follows: 

Gonads 0.25 

Breast 0.15 

Red bone marrow 0.12 

Lung 0.12 

Thyroid 0.03 

Bone surfaces 0.03 

Remainder 0.06 

Whole body 1.00 

It is imporatant to note that the weighting factors have been 

revised in the 1990 recommendations of the ICRP (ICRP 60). The 

1977 values are used in the 1991 revision to 10 CFR Part 20.

ICRP Publication 26 states, "No practice shall be adopted unless 

its introduction produces a net benefit." This concept is 

called: 

A) optimization 

B) maximimzation 

C) minimization 

D) justification 

E) realization 


Once a practice involving radiation exposure has been justified 

as described, the process of optimization is implemented to 

determine an appropriate level of radiation protection. 

Cost-Benefit Analysis in radiation protection is addressed in 

ICRP Publication 37.

For students under the age of 18, the NCRP recommends that the 

whole body radiation dose from educational activities be limited 

to: 

A) 0.1 rems/yr 

B) 0.17 rems/yr 

C) 0.3 rems/yr 

D) 0.5 rems/yr 

E) 5.0 rems/yr 


This recommendation is adopted in both NRC and DOE radiation 

protection regulations. It appears in NCRP Report No. 116 

(1993), "Limitation of Exposure to Ionizing Radiation", which 

superseded Report No. 91 (1987).

To limit possible exposure to radiation from television 

receivers, the NCRP recommends that children sit no closer than: 

A) 6 feet 

B) 5 feet 

C) 4 feet 

D) 3 feet 

E) 2 feet 


The flyback transformer in a television set produces x-rays. The 

FDA limits the exposure rate at the surface of television sets 

today to 0.1 mR/hr.

The FDA standard for microwave oven leakage at 5 cm or more from 

the external surface of the oven, prior to sale is: 

A) 1 mW/cm^2 

B) 5 mW/cm^2 

C) 10 mW/cm^2 

D) 20 mW/cm^2 

E) 100 mW/cm^2 


Once placed in operation, the limit is raised to 10 mW/cm^2, 

which is the TLV for microwaves.

In emergency planning, a "protective action guide" is defined as: 

A) the radiation level corresponding to the 

"Radiation Protection Guide" 

B) the radiation dose which should not be 

exceeded without careful consideration of the 

reasons for doing so 

C) the projected dose which warrants protective 

action to be taken 

D) the maximum radiation dose which can be 

received without an significant deleterious 

somatic effects 

E) the projected levels at which every effort 

should be make to reduce the dose as far as 

possible 


If it is anticipated that the protective action guides (PAGs) 

will be exceeded, a protective action recommendation (PAR) such 

as sheltering or evacuation within certain sectors and radii will 

be made. PAGs are expressed in units of dose equvalent, and can 

be found in EPA 400 (1993).

Lead and polyethylene are available to shield a source emitting 

6.1 MeV gammas and neutrons of an average energy of 2.5 MeV. 

Which shielding arrangement listed below would be expected to 

yield the lowest overall dose rate? 

A) polyethylene followed by lead 

B) lead only 

C) polyethylene only 

D) lead followed by polyethylene 

E) no shielding is necessary since the 12" air 

gap will sufficiently scatter/attenuate the 

neutrons 


In this scenario, the fast neutrons should be shielded first by 

the hydrogenous polyethylene, then the lead to shield both the 

capture gammas and the 6.1 MeV gammas.

State the purpose of the main steam line radiation monitors at a 

BWR. 

A) detection of gross fuel failure 

B) quantify steam release rates 

C) indicate reactor power during accidents 

D) serve area monitors near steam lines 

E) quantify off-gas 


During reactor fuel failure, a large amount of gamma-emitting 

fission products are released to the reactor coolant and exit the 

reactor through the main steam lines. An increase in the gamma 

redings at this location serves as an indication of fuel failure.

Optimization techniques can be used to assure that: 

A) a radiation protection practice keeps 

radiation exposures as low as reasonably 

achievable (ALARA) 

B) the dose and resultant radiation detriment 

are minimized 

C) the gross monetary benefit of a practice 

involving ionizing radiation is maximized 

D) a cost of achieving a selected level of 

radiation protection is minimized 

E) the basic production cost is minimized 


Optimization is a technique recommended by the ICRP in 

Publication 26 (1977). Cost-Benefit analysis in radiation 

protection is discussed in detail in Publication 37.

The radionuclide that is the main cause of shutdown radiation 

fields at nuclear power plants is: 

A) N-16 

B) Cs-137 

C) Co-58 

D) Co-60 

E) Xe-135 


Co-60 is an activation product from the activation of Co-59 and 

the actvation of iron. Co-59 is present in nuclear power plants 

in valve seats and control rod blade roller pins. Iron, of 

course, is an important component of stainless steel. Co-60 

decays by beta, with a 1.17 and a 1.33 MeV gamma. It has a 5.27 

year half-life.

Comparative assessment of United States and foreign nuclear power 

plant occupational dose experience has indicated that reductions 

in out-of-core radiation fields can result in substanial 

reductions in occupational doses. Of the following actions, the 

one that is the LEAST effective in reducing out-of-core radiation 

fields is: 

A) hydrogen water chemistry 

B) control of impurities in reactor coolant 

C) preconditioning of out-of-core surfaces 

(polishing,prefilming) 

D) reduction or elimination of cobalt in reactor 

system components 

E) chemical decontamination 


Hydrogen water chemistry is used to regulate reactor performance, 

rather than to reduce radiation fields. The other distractors 

are all ALARA engineering methods.

If personnel with doses less than 100 mrem/year are excluded, the 

average annual exposure for nuclear reactor workers is typically: 

A) 400-800 mrem 

B) 750-1500 mrem 

C) 1200-2400 mrem 

D) 2000-3000 mrem 

E) 2700-4000 mrem 


This question is based on circa-1986 estimates. In the 1990's, 

due to the implementation of lower dose limits, the estimates 

could get lower.

In general, for a hot particle on the skin, the principal 

contributor to dose to the skin in the vicinity of the particle 

is: 

A) the neutron radiation emitted from the 

particle 

B) the gamma radiation emitted from the particle 

C) the alpha radiation emitted from the particle 

D) the beta radiation emitted from the particle 

E) the conversion electron emitted from the 

particle 


Hot particles are typically small pieces of activated metal or, 

in some cases, fuel fragments. In power reactors they are more 

often than not composed of Co-60. It is the beta particles which 

produce the most skin dose, since the probability of interaction 

is much higher than for gammas.

Prior to 1988, explicit recommendations on limits for radiation 

exposure of skin by hot particles were provided by: 

A) the ICRP, but not the NCRP 

B) both the NCRP and the ICRP 

C) the NCRP but not the ICRP 

D) neither the NCRP nor the ICRP 

E) the ICRU, NCRP, and ICRP 


Hot particles did not receive much attention until the 

mid-1980's, most likely because of improvements in detection 

methods. Exposures were common enough that the NCRP issued 

Report No. 106 on hot particle exposures in 1989.

Radiobiological evidence suggests that, when compared to more 

uniform irradiation by the same quantity of radioactive material, 

highly localized beta irradiation of skin, such as from a 

particle on the skin: 

A) is less likely to cause skin cancer 

B) is more likely to cause skin cancer 

C) is about equally likely to cause skin cancer 

D) is likely to cause erythema within a few 

hours 

E) is likely to cause a small necrotic lesion on 

the skin of an individual after only a few 

hours exposure 


Research has shown that irradiation from hot particles, discrete 

beta-emitting activation or fission product particles, are much 

more likely to create minor cosmetic changes to the skin than to 

cause skin cancer.

In general, the most important source of occupational radiation 

exposure at nuclear power plants is: 

A) gamma radiation from the core 

B) long-lived fission product activity 

C) neutron activation product activity 

D) short-lived fission product activity 

E) neutron radiation from the core 


Since activation products (most notably Co-60) are present for 

the life of the plant, rather than just during operation, they 

contribute the most to occupational radiation exposure. Work on 

plant components during shutdown often involves exposure to these 

activation products.

A regional low-level waste compact's burial site requires all 

High Integrity Containers to be filled to at least 85% volume. 

What is the primary technical basis for this requirement? 

A) self-shielding/ALARA 

B) post burial water intrusion 

C) reduce annual shipping costs 

D) conservation of site burial costs 

E) limit thermal wattage 


The critical exposure pathway from a low-level radioactive waste 

burial site is through the water supply. The stability of the 

wasteform in the disposal atmosphere is an important factor in 

preventing release of the contents. Without a significant volume 

of the HIC filled, the container could collapse from overburden 

and release its contents.

When communicating information regarding a radiation accident to 

the general public, which of the following approaches is MOST 

effective? 

A) avoid embarrassment by reducing the actual 

impact of the event 

B) let the media interpret and disseminate the 

pertinent information 

C) emphasis should be placed on influencing the 

public's actions, rather than informing the 

public 

D) dissemination of public information must 

reflect openness, correctness, and candor 

E) circumvent criticism by revealing only the 

most innocuous factors related to the event 


The public information officer must establish the trust of the 

public. Communication should be frequent, in addition to the 

other factors listed.

At a point outside a thick photon radiation shield the exposure 

due to primary photons is 0.25 of the exposure from secondary 

photons. What is the buildup factor at that point? 

A) 5 

B) 4 

C) 3 

D) 2 

E) 1 


Since the buildup factor is the ratio of all photons at a point 

outside the shield to primary, unscattered photons at that point, 

B = all/primary 

B = (1 + 0.25)/0.25 

B = 5

The ordering of the following shielding materials to provide 

maximum protection from a fast neutron source starting at a point 

closest to the source should be: 

A) lead, boron, plastic 

B) plastic, boron, lead 

C) boron, plastic, lead 

D) boron, lead, plastic 

E) plastic, lead, boron 


The hydrogenous plastic is used to thermalize the neutron 

spectrum, then the boron captures the neutrons. The lead is 

present to shield gammas from activation products (capture 

gammas).

What is the cadmium absorption edge? 

A) the energy level at which the neutron capture 

cross-section of cadmium shows a steep 

increase 

B) the energy level at which the electron 

capture cross-section of cadmium shows a 

steep increase 

C) the energy level at which the neutron capture 

cross-section of cadmium shows a steep 

decrease 

D) the energy level at which the electron 

capture cross-section of cadmium shows a 

steep decrease 

E) the energy level at which the photon 

absorption cross-section of cadmium shows a 

steep decrease 


The cadmium absorption edge occurs at about 0.2 MeV.

Which of the following statements about fume hoods is INCORRECT? 

A) the inside of the hood and the ducts should 

be as easy to clean as practicable 

B) the air flow should be sufficient to prevent 

the escape of hood air to the workplace 

C) the design should provide for smooth air 

flow, without significant eddies 

D) the gas, water, and electrical appliances 

should be operated from inside the fume hood 

E) the exhaust fan should be placed downstream 

of the filters 


The operator should not have to adjust these hood functions from 

the inside of the hood, due to the presence of a hazardous 

atmosphere in the hood. This would be particularly true during 

an unanticipated release inside of the hood or if the hood 

failed. All other distractors are valid.

A locking access control system is installed at the entrance to a 

food irradiation cell which uses a 10,000 curie Co-60 source. In 

accordance with 10 CFR 20, which posting should be placed at the 

entrance of the cell? 

A) Caution - Radiation Area 

B) Caution - High Radiation Area 

C) Grave Danger - Very High Radiation Area 

D) Danger - Very High Radiation Area 

E) Danger - High Radiation Area 


10 CFR Part 20 requires this posting when the absorbed dose rate 

could exceed 500 rad/hr at one meter from the source or the 

surface that the radiation penetrates. This source unshielded 

would produce over 15,000 rad/hr at one meter.

If the most restrictive airborne radionuclide at a facilty has a 

DAC of 7 E-12 microcuries/ml, a continous air monitor at the 

facilty should have an alarm set point at a count rate which 

indicates an airborne concentration of: 

A) 7.00 E-13 microcuries/ml 

B) 1.75 E-12 microcuries/ml 

C) 2.25 E-12 microcuries/ml 

D) 5.25 E-12 microcuries/ml 

E) 7.00 E-12 microcuries/ml 


Since personnel monitoring is required if an individual could 

exceed 10% of the annual limits, it makes sense to have in place 

a detection mechanism to identify when that threshold is reached. 

7.00 E-13 is 10% of the stated DAC in the question. DOE 

currently requires posting of airborne radioactivity areas at 0.1 

DAC (DOE N5480.6, 1992).

Which one of the following radiological operations is MOST likely 

to require the use of a remote handling device? 

A) oral adminstration of a 100 millicurie I-131 

solution to a medical patient 

B) handling a PuBe source during calibration of 

a neutron dose equivalent rate meter 

C) eluting a dose of Tc E99m from a radioisotope 

generator 

D) source checking a beta-gamma contamination 

monitoring instrument 

E) injection of a 5 millicurie P-32 solution as 

sodium phosphate to a medical patient 


This operation typically involves the highest radiation dose 

equivalent rates of those listed. None of the distractors 

routinely employs remote handling devices.

The maximum protection factor that can be used against tritium 

oxide when wearing a supplied air hood is: 

A) 2 

B) 10 

C) 50 

D) 100 

E) 1000 


Since absorption through the skin constitutes about one-half of 

the dose from exposure to tritium oxide, the maximum PF for 

inhalation protection is 2. Respiratory protection factors are 

found in 10 CFR Part 20 Appendix A.

Actions taken during a spill of highly enriched fissile material: 

A) should ensure that the spilled material does 

not reach a critical condition because of 

geometry and/or reflection 

B) should require the immediate evacuation of 

all personnel from the area affected 

C) should require securing the area and turning 

off the ventilation system 

D) should require the collection and confinement 

of the material through whatever means are 

immediately available 

E) should include immediate notification of the 

NRC 


Choices A through D are all valid responses, but A is the most 

important since the release of energy from a criticality accident 

can be fatal. Contamination is a secondary concern.

For regulatory compliance purposes, the "total organ dose 

equivalent" is BEST represented by the sum of: 

A) the deep dose equivalent and the committed 

dose equivalent 

B) the deep dose equivalent and the committed 

effective dose equivalent 

C) the effective dose equivalent and the deep 

dose equivalent 

D) the shallow dose equivalent, the deep dose 

equivalent, and the effective dose equivalent 

E) the shallow dose equivalent, the deep dose 

equivalent, and the committed effective dose 

equivalent 


The annual limit for the total organ dose equivalent (TODE) is 50 

rem. It is the sum of the committed dose equivalent (from 

internal sources) and the deep dose equivalent (from external 

sources.

The "institutional monitoring period" for a low-level radioactive 

waste disposal site which utilizes near-surface disposal is: 

A) five years 

B) fifty years 

C) one-hundred years 

D) three-hundred years 

E) five-hundred years 


After closure, the site is monitored for a period of five years 

by the operator of the site. It is then turned over to the state 

for the institutional monitoring period of 100 years. After 100 

years, the state may lift access restrictions on the site. These 

requirements are set forth in the Low Level Waste Policy Act as 

amended (1985) and 10 CFR Part 61.

The radionuclide used to improve optical instrument performance 

through improved light processing by the lens is: 

A) Neptunium 

B) Uranium 

C) Thorium 

D) Tritium 

E) Cesium 


Thorium is added to optical instrument glass in concentrations up 

to 30% by weight to provide certain optical properties.

After a criticality accident, an individual's exposure to 

neutrons can be measured by placing a gamma detecting survey 

instrument probe over the abdomen and doubling the individual 

over the probe. A reading of 0.1 mr/hr on a GM probe indicates an 

absorbed neutron dose of: 

A) 5 rem 

B) 10 rads 

C) 15 rads 

D) 25 rem 

E) 30 rads 


This technique should be followed by more accurate measurements 

on blood and urine samples for Na-24 or hair samples for P-32. 

Metal objects on an individual should also be measured for 

induced radioactivity if neutron exposure has occured. 

(NCRP 65, page 29)

The target and filter material used in most x ray mammography 

machines is, respectively: 

A) molybdenum, molybdenum 

B) tungstun, molybdenum 

C) tungston, rhodium 

D) rhodium, rhodium 

E) molybdenum, rhodium 


Health Physics Journal Vol 69 No 5 (Henkle 1995): 

"Multiple studies of x-ray spectrum influence on radiation dose 

to patient and quality of the mammographic image has lead to 

widespread acceptance of dedicated mammographic x-ray units 

employing molybdenum-target x-ray tubes and molybdenum filters 

90.03 mm thick) for the x-ray beam."

The transmission of characteristic x-rays through the same 

element filter as the target results in a nearly monoenergetic 

output of the x-ray tube around: 

A) 100 to 150 keV 

B) 20 to 30 keV 

C) 2 to 5 keV 

D) 17 to 22 keV 

E) 1000 to 1700 keV 


Health Physics Journal Vol 69 No 5 (Hendee 1995)

Most newer mammographic units contain a moving grid to reduce 

scattered radiation, which if not used would result in a 

reduction of _____ in contrast of the image produced. 

A) 5 - 10% 

B) 60 - 75% 

C) 10 - 20% 

D) 70 - 80% 

E) 30 - 45% 

The correct answer is: E 

Reduction in image contrast caused scattering radiation which is 

40 - 80% of the radiation exiting the tissue. 

Health Physics Journal Vol 69 No5 (Hendee 1995)

The effective dose from a single routine computerized tomography 

(CT) scan examination of the chest in the UK on the average is: 

A) 2 Gy 

B) 43 mGy 

C) 125 mGy 

D) 8 mGy 

E) 27 Gy 


Health Physics Journal Vol 69 No 5 (Webster 1995)

Theraputic radionuclides are used to deliver large doses of 

radiation in the treatment of cancer. Brachytherapy includes: 

A) placement of radioactive material in the 

brachial artery 

B) placement of radioactive material in direct 

contact with tumors 

C) inhalation of radionuclide to treat cancer of 

the bronchi 

D) irradiation of cancer tumors with external 

sources of radiation 

E) irradiation of bronchi by external radiation 

sources to treat lung cancer 


"..involves the placement of radioactive material in direct 

contact with tumors. It is reserved for tumors that are accesible 

via natural body cavities, or on body surfaces. I-125, Cs-137, 

Ir-192 and Au-198 are commonly used brachytherapy materials. 

Contemporary Health Physics: Problems and Solutions 

Joseph Bevlacqua

Commonly used brachytherapy radioactive materials are: 

A) I-125, Ir-192 and AU-198 

B) I-131, Co-60 and Eu-154 

C) Rb-88, Cs-137 and Ir-192 

D) Kr-88, Ar-41 and Co-60 

E) I-125, Pm-149 and Ba-142 



Joseph Bevelacqua

Radiation leakage from an x-ray tube is higher in energy than 

that of the primary radiation beam. This difference in energy 

level is due to: 

A) the proximity of the leakage location to the 

origin of the x-rays 

B) acceleration of the leakage x-rays by the 

tube voltage 

C) the filtering of the primary beam as it 

passes through the beam housing 

D) the interaction of the x-rays with the tube 

housing 

E) the interaction of the x-rays with the 

magnetic fields generated in the tube 



Joseph Bevelacqua

The most sensitive technique for analyzing intakes of C-14 are: 

A) exhalation 

B) blood sample 

C) urinalysis 

D) fecal analysis 

E) whole body count 



Joseph Bevelacqua

The dominant external radiation hazard in Fuel cycle facilities 

requiring work with unshielded forms of uranium is: 

A) alpha 

B) photoelectric gammas 

C) thermal neutrons 

D) fast neutrons 

E) beta 



Joseph Bevelacqua

You have been assigned to cover a fuel re-rack job at a PWR. The 

types of radiation you should be concerned with during the job 

are: 

A) gamma and beta 

B) gamma, beta and neutron 

C) gamma, beta and alpha 

D) gamma, beta, neutron, and alpha 

E) beta and alpha 


You should be concerned with all four. Spent fuel pools can 

contain corrosion products (beta-gamma), fuel elements and 

pellets (beta-gamma-alpha), fail ful (alpha-beat) and neutron 

sources (alpha-neutron). It is likely you will not be aware of 

everything in the pool so you should anticipate problems from any 

of the four.

Power reactors do not routinely count smears for alpha activity 

during general area surveys. This practice is based on: 

A) the amount of alpha activity in the reactor 

coolant system 

B) the results of the alpha to beta-gamma 

isotopic makeup identified in the 10CFR61 

analysis 

C) the history of the plants nuclear fuel 

performance 

D) the results of alpha-beta-gamma surveys of 

radioactive sources in accordance with 

10CFR35 

E) the lack of sensitive instruments to measure 

alpha activity 


Routine survey smears are not counted for alpha if the 10CFR61 

Low level Waste Classification analysis of waste streams 

indicates a plant specified ratio (typical is 500:1) of 

beta-gamma to alpha on all waste streams.

A worker has been contaminated by a hot particle, the skin dose 

assigned to the worker is determined using the guidelines 

established in NCRP 106. The area and depth the dose is 

calculated to is: 

A) 1 cm2 and 300 mg/cm2 

B) 100 cm2 and 1000 mg/cm2 

C) 1 cm2 and 7 mg/cm2 

D) 1 mm2 and 7 mg/cm2 

E) 1 mm2and 1000 mg/cm2 


NCRP 106

The occupation limit for radon exposure in the United States is: 

A) 4 WLM/year 

B) 1.3 E5 MeV alpha/1 liter of air 

C) 210 pci/liter per year 

D) 0.02 WLM/year 

E) 2 R/yr 



Joseph Bevelacqua

In non-power reactors the radionuclide that is the principal 

environmental emission is: 

A) Fe-59 

B) Mn-56 

C) Co-60 

D) Sb-124 

E) Ar-41 


Ar-41 generated from neutron interaction with Ar-40 in air. Found 

predominantly in facilities specifically designed for neutron 

beam experiments. 

Radiation protection at Nuclear Power Plants 

Constantine J. Maletskos

Monitoring of nuclear power plant effluents during normal 

operations includes airborne and liquid pathways. Monitoring of 

liquid effluent is accomplished by three methods: 

A) base-time, grab sample, filtration processing 

B) real-time, grab sample, composite sampling 

C) lag-time, in-line sampling, separation 

sampling 

D) post-time, random sampling, distillation 

sampling 

E) lead-time, continuous sampling, vitrification 

sampling 


In some cases, liquid effluents are monitored using all three 

methods. 

Radiation Protection at Nuclear Power Plants 

Constantine Maletskos

The government document that specifies the noble gas 

concentration range for monitoring several configurations for 

PWRs and BWRs is: 

A) Regulatory Guide 8.30 

B) 10CFR100 

C) Regulatory Guide 1.97 

D) 10CFR50 

E) Regulatory Guide 1.85 


Regulatory Guide 1.97 is the document that specifies the noble 

gas concentration range for monitoring several configurations for 

PWRs and BWRs.

Sample lines for plant vents must be designed to minimize sample 

line losses. As a general rule, the sample line should be 

designed to: 

A) maximize velocity and diameter, while 

minimizing distance 

B) maximize velocity and distance, while 

minimizing diameter 

C) maximizing velocity and distance, while 

minimizing tortuous paths 

D) maximizing distance while minimizing diameter 

and tortuous paths 

E) maximizing velocity while minimizing diameter 

and tortuous paths 


Depending on the line configuration, these factors may result in 

line losses ranging from 0 to 100% (ANSI,1969) 

Radiation Protection at Nuclear Power Plants 


Liquid effluents are NOT considered: 

A) a significant contribution to the amount of 

activity released during normal operations. 

B) an environmental sample method 

C) an accident-release pathway 

D) for in-line monitoring applications 

E) when calculating radioactive release to the 

environment 


Because of this, additional instrumentation for accident 

monitoring is not used. Releases of liquid effluents are normally 

under manual control because they involve the discharge from 

holdup tanks. 

Radiation protection at Nuclear Power Plants 


The code of Federal Regulations, 40CFR190, requires that nuclear 

power plants maintain the dose to the maximally exposed member of 

the public to less than: 

A) 1 mSv/yr 

B) 0.5 mSv/yr 

C) 0.1 mSv/yr 

D) 0.25 mSv/yr 

E) 5 mSv/yr 


D) 25 mrem

During the early phase of an accident EPA 400-R-92-001 limits 

workers performing emergency services to an effective dose 

equivalent for all activities at: 

A) 50 mSv 

B) 100 mSv 

C) 20 mSv 

D) 250 mSv 

E) 500 mSv 


A) 5 Rem

During the early phase of an accident EPA-400-R-92-001 limits 

workers performing emergency services to an effective dose 

equivalent while protecting valuable property to: 

A) 200 mSv 

B) 50 mSv 

C) 20 mSv 

D) 100 mSv 

E) 5 mSv 


D) 10 Rem

According to 10CFR19, all individuals who are employed by a 

company must receive instruction in the health protection 

problems associated with excessive exposure to radiation if they 

are likely to receive: 

A) 10 mSv 

B) 1 mSv 

C) 5 mSv 

D) 10% of annual dose limt 

E) 0.5 mSv 


B) 100 mrem 10CFR19.12(a)

A radioactive shipment is being prepared for transport in the 

truck bay of your facility. You do not need to control the area 

as a high radiation area as defined in 10CFR20 if the following 

are met: 

A) package does not remain in area more than 1 

hour and dose rate at 1 meter does not exceed 

0.5 mSv 

B) package does not remain in area more than 3 

hours and dose rates at 30 cm does not exceed 

10 mSv 

C) package does not remain in area more than 3 

days and dose rate at 1 meter does not exceed 

0.1 mSv 

D) package does not remain in area more than 7 

days and dose rates at 30 cm does not exceed 

0.5 mSv 

E) package does not remain in area more than 5 

working days and the dose rate 1 meter does 

not exceed 1 mSv 


C) 10CFR20.1601(e)

The effective dose equivalent allowed by EPA Protective Action 

Guides for life saving or protection of large populations is: 

A) 25 rem) 

EPA-400-R-92-001

The effective dose equivalent allowed by EPA Protective Action 

Guides for life saving or protection of large populations where 

the individual is a volunteer and is fully aware of the risks 

involved: 

A) >250 mSv 

B)

You have received a package containing radioactive material. The 

highest smearable contamination on the external surface of the 

package is 3,000 dpm/100 cm2. You should notify: 

A) all individuals who handled package and the 

NRC Alert team 

B) the shipper and the NRC Washington office of 

Radioactive Material Shipping 

C) the originating activity and the NRC Regional 

office 

D) the final carrier and the NRC Regional office 

E) the addressee of the package and the 

originating activity 


D) 10CFR20.1900

The amount of tritium allowed by 10CFR20 that can be disposed of 

in sanitary sewage is: 

A) 74 GBq in a quarter 

B) 37 GBq in a month 

C) 1000 GBq in a year 

D) 370 GBq in a quarter 

E) 185 GBq in a year 


5 ci/yr * (3.7 E10 Bq/ci) = 1.85 E11 Bq or 185 GBq

The NRC must receive immediate notification if an event involving 

byproduct, source, or special nuclear material possessed by the 

licensee may have caused or threatens to cause: 

A) eye dose equivalent of 0.15 Sv or more 

B) total effective dose equivalent of 0.25 Sv or 

more 

C) shallow dose equivalent of 0.25 Sv or more 

D) an intake of 3 times the annual limit 

E) extremity dose equivalent of 0.5 Sv or more 


B) 10CFR20.2202

An individual has received an intake of 2 ALIs in the last 24 

hours. You must notify the NRC within: 

A) 24 hours 

B) an hour 

C) one week 

D) ten working days 

E) a month 


A) 10CFR20.2202

The class designation (D, W, and Y) given in the "Class column" 

of Appendix B to part 20 applies only to: 

A) stochastic ALIs and DACs 

B) airborne and effluent release to the general 

environment 

C) inhalation ALIs and DACs 

D) oral ingestion ALIs 

E) releases to sewers 


Classes based on retention of an aerosol of 1 mircometer AMAD 

particles in the pulmonary region of the lung.

The class "D" in Appendix B to part 20 applies to a range of 

clearance half lives: 

A)

The non-stochastic ALIs listed in Appendix B to part 20 are 

designated: 

A) by an asterisk 

B) with the name of the organ limited by the 

dose 

C) by the letters "NS" after the value 

D) by parentheses 

E) by footnote number 3 


B) Appendix B to part 20 Table 1 notes: 

"When an ALI is determined by the non-stochastic dose limit to an 

organ, the organ or tissue to which the limit applies is shown, 

and the ALI for the stochstic limit is shown in parentheses"

The concentration values given in Table 2 Effluent Concentrations 

in Appendix B of part 20 are equivalent to the radionuclide 

concentrations which, if inhaled or ingested continuously over 

the course of a year, would produce a total effective dose 

equivalent of: 

A) 0.1 mSv 

B) 5 mSv 

C) 1 mSv 

D) 0.5 mSv 

E) 2 mSv 


D) 50 mrem or 0.5 mSv

For those radionuclides for which submersion dose is limiting, 

the occupational DAC in Appendix B of part 20 was divided by a 

factor of 219. The factor of 219 is composed of a factor of 50 to 

relate the 5-rem annual occupational dose limit to the 0.1 rem 

limit for members of the public, and a factor of 4.38 that 

relates: 

A) occupational exposure for 2000 hrs/yr to full 

time exposure 

B) age considerations of individuals in 

submersion gas 

C) clearance rates of workers for various work 

activites 

D) daily exposure to yearly exposure 

E) internal exposure to external exposure 


factor 4.38 relates occupational exposure of 2000 hours to full 

time exposure of 8,760 hours per year

The Department of Energy's yearly administrative control level 

for Total Effective Dose Equivalent for all DOE activities is: 

A) 1 Rem 

B) 2 Rem 

C) 0.5 Rem 

D) 5 Rem 

E) 0.1 Rem 


DOE Radiological Control Manual Article 211

A whole body counting report identifies a CDE to the lung of 45 

Rem. If the deep dose exposure to the individual was 0.75 Rem the 

individual's Total Effective Dose Equivalent is: 

A) 5.25 rem 

B) 45.75 rem 

C) 11.26 rem 

D) 6.15 rem 

E) 2.1 rem 


Wt for lung is 0.12 (10CFR20) CDE = 45 rem 

CEDE = CDE * Wt = 45 rem * 0.12 = 5.4 rem 

TEDE = DDE + CEDE = 0.75 rem + 5.4 rem = 6.15 rem

A DOE radiation worker has a lifetime exposure that exceeds her 

age. In accordance with the DOE Radiological Control Manual, the 

workers exposure for the year shall be limited to: 

A) 2 mSv 

B) 1 mSv 

C) 5 mSv 

D) 20 mSv 

E) 10 mSv 


1 Rem is the limit convert to mSv. 1 Sv = 100 Rem

The DOE beta-gamma removable contamination limit is: 

A) 16.7 Bq/100 cm2 

B) 8.3 Bq/100 cm2 

C) 0.83 Bq/100 cm2 

D) 33.4 Bq/100 cm2 

E) 83.5 Bq/100 cm2 


1000 dpm/100 cm2 = 16.7 Bq/100 cm2

The best way to reduce the volume of waste HEPA filters is to 

prolong the life of those in use. One of the recommended actions 

is to: 

A) air blow filters to reduce DP across HEPA 

B) reverse filter when DP is high 

C) use pre-filters and replace when DP is high 

D) backflow air to reduce DP 

E) decrease air flow through unit 


EPRI Radwaste Desk Reference Question 1116: Prefilters, which 

collect debris and large particles of dust, prevent clogging of 

the filters. They extend the life of a HEPA by an order of 

magnitude.

To remain in compliance with 10CFR61, you need to resample your 

waste streams in all of the situations below EXCEPT: 

A) water chemistry parameters have changed 

B) after a fuel leak 

C) after a crud burst 

D) semi-annually for confirmation 

E) when chemical decontamination may have 

removed some radionuclides selectively 


Should resample quarterly and yearly for confirmation. 

EPRI Radwaste Desk Reference Question 1626

A Notice of Violation will not be issued when an individual 

receives a hot particle exposure that is equal to or less than 

the beta emission criteria of: 

A) 25 microcurie-hours 

B) 50 rad at 7 mg/cm2 over 1 cm2 

C) 10 rad at 1 mg/cm2 over 1 cm2 

D) 100 microcurie-hours 

E) 75 microcurie-hours 


Corresponds to 1.0 E10 beta particles 

NRC Information notice IN90-48

A criticality accident has occured at a facility. You have been 

assigned to determine which individuals have received a large 

dose. Using a GM probe you obtain 0.5 mr/hr above background on 

an individual. Thei estimated dose is: 

A) background 

B) 0.5 mrad 

C) 5 rad 

D) 25 rad 

E) 75 rad 


Thumbrule=> 0.1 mr/hr using GM probe on individuals exposed 

during criticallity accident is 15 Rad. 

(0.5 mr/hr) * (15 rad) / (0.1 mr/hr) = 75 rad

After exposure rates from radioactive fallout (from nuclear 

weapons) have begun to decrease, a rough idea of future rates can 

be gained by using the: 

A) curie meter rem rule 

B) 7:10 rule 

C) submersion dose calculation 

D) EPA PAG recommendations 

E) quick sort survey 


This rule states that for every seven-fold increase in time after 

detonation, there is a ten-fold decrease in exposure rates. 

The Health Physics and Radiological Health Handbook 1992

Radiation exposure rates produced by a television receiver from 

any external surface shall not exceed: 

A) 0.5 mr/hr at 30 cm 

B) 1 mr/hr at 1 m 

C) 2 mr/hr at 30 cm 

D) 0.5 mr/hr at 5 cm 

E) 0.1 mr/hr at 5 cm 


21 CFR 1020.10

The leakage radiation from a diagnostic source assembly measured 

at a distance of 1 meter in any direction from the source shall 

not exceed: 

A) 1000mr/hr 

B) 2 mr/hr 

C) 100 mr/hr 

D) 20 mr/hr 

E) 10 mr/hr 


100 mr in 1 hour when the x-ray tube is operated at the leakage 

technique factors. 

21 CFR 1020.30

Exemtions to leak testing sealed sources according to 10CFR31.5 

are: 

1. < 10 microCi BG 

2. Kr only 

3. < 1 E 3 microCi alpha 

4. Tritium only 

5. Not in use for > 6 months 

A) 1,2,3 

B) 2,4 

C) 2,3,4,5 

D) 2,4,5 

E) 1,2,5 


Krypton is a gas and Tritium is a low beta emitter and is hard to 

measure on a smear survey. 

10CFR31.5

What neutron quality factor did the BEIR V report use to 

calculate dose equivalent? 

A) 3 

B) 5 

C) 10 

D) 17 

E) 20 


(BEIR V)

The effectiveness of radiation therapy can be increased by: 

A) heat 

B) chemicals 

C) type of radiation 

D) dose rate or dose fractionation 

E) All of the above 


All the listed factors affect the way target cells react to 

ionizing radiation.

According to 10 CFR 20 radiological surveys should be performed 

to evaluate: 

A) The extent of the radiation levels 

B) The concentrations of radioactive materials 

C) The quantities of radioactive materials 

D) The potential radiological hazards that could 

be present 



(10 CFR 20)

An accessible area as defined by the NRC for the purpose of 

posting radiological areas is: 

A) Any area where any part of the bady can be 

exposed to radiation 

B) Any area where any part of the whole body can 

be exposed 

C) Any area that can be reasonably occupied by a 

major portion of the whole body 

D) Any area where personnel can have access to 

through deliberate or inadvertant action 

which may lead to radiation exposure 

E) Any area capable of human habitation 


(Reg. Guide 8.38, Page 2)

Which of the following Regulatory Guides might be of use to a 

female employee considering declaring pregnancy? 

A) 1.145 

B) 8.13 

C) 8.25 

D) 8.34 

E) 8.35 


Regulatory Guide 8.13 is "Instructions Concerning Prenatal 

Radiation Exposure".

Which one of the following shapes respresents the greatest hazard 

for a criticality accident? 

A) A sphere 

B) A disk 

C) A rectangular block 

D) A long thin cylinder 

E) A pyramid 


Safe geometries include shapes that favor high neutron leakage 

out of the critical mass such as a flat disk or a long thin 

cylinder

Which of the following is NOT true concerning the handling or 

radiodine? 

A) Work in a well ventilated room 

B) Wear two pairs of rubber gloves because 

radiodine can diffuse through rubber and 

plastic 

C) Keep vials containing radiodine closed when 

not in use to reduce airborne 

D) Decontaminate spills with a low PH solution 

E) Airborn iodine exists as elemental iodine, 

organic iodine, and iodine absorbed on 

aerosols 


The volatility of I125 is enhanced at low a PH. Decontamination 

of spills should use a .1 M NaI, .1 M NaOH, and .1 M Na2S203 to 

stabilize the material.

According to ICRP publication 60, the "equivalent dose" to a 

tissue is the product of the absorbed dose averaged over the 

tissue and: 

A) an appropriate quality factor 

B) an appropriate radiation weighting factor 

C) an appropriate tissue weighting factor 

D) an appropriate nonstochastic risk coefficient 

E) an appropriate stochastic risk coefficient 


The 1990 recommendations have replaced the 1977 concept of 

quality factor with radiation weighting factor. The radiation 

weighting factors from ICRP 60 are as follows: 

Radiation 

Radiation Weighting Factor 

X, gamma, beta 1 

Alpha, multiple-charged particles, 

fission fragments, heavy particles 

of unknown charge 20 

Neutrons of unknown energy 10 

High energy protons 10

According to the EPA, a home should be remediated if the average 

long term Radon concentration exceeds? 

A) 1 pCi/liter 

B) 4 pCi/liter 

C) 10 pCi/liter 

D) 50 pCi/liter 

E) 50% of the DAC assuming an occupancy factor of 1/5 


EPA report OPA-86-004 (1986) recommends 4 pCi/liter

The goal of the ICRP is setting radiation protection standards is 

to: 

A) prevent stochastic and non-stochastic effects 

B) prevent non-stochastic effects and limit 

stochastic effects to an acceptable level of 

risk 

C) prevent stochastic effects and limit 

non-stochastic effects to an acceptable level 

of risk 

D) provide a basis to prevent litigation 

E) limit genetic effects to less than 1 birth 

defect in 100,000 live births 


There is no way to prevent stochastic effects. Radiation doses 

are limited to minimize the probability of stochastic effects, 

such as cancer.

A shipment of radioactive materials over public highways 

containing a type B package would be regulated by: 

A) the NRC 

B) the DOT 

C) the EPA 

D) both the NRC and DOT 

E) both the NRC and EPA 


The NRC regulates the package under 10 CFR 71 and the DOT 

regulates the shipment under 49 CFR 171-179

Protective actions for nuclear accidents are grouped into which 

of the following three time phases? 

A) Early, Intermediate, and Recovery 

B) Initial, Intermediate, and Recovery 

C) Initial, Interdiction, and Recovery 

D) Beginning, Middle, and End 

E) Early, Interdiction, and Recovery 


(EPA-400)

The tissue weighting factor for the bone surfaces according to 10 

CFR 20 is: 

A) .25 

B) .12 

D) .06 

E) .03 


(10 CFR 20)

In 10 CFR 20 the weighting factor of .3 for remainder organ 

includes how many organs? 

A) 3 

B) 5 

C) 6 

D) 10 

E) 15 


(10 CFR 20)

According to NUREG-0713, which of the following occupations has 

the highest average annual individual dose? 

A) Commercial nuclear power 

B) Manufacturing and distribution of radioactive 

materials 

C) Low-level waste disposal 

D) Industrial Radiography 

E) Nuclear fuel fabrication 


According to NUREG-0713, the average dose per worker is 540 mrem 

for industrial radiography.

When is summation of external and internal doses required by 10 

CFR 20? 

A) If external monitoring is required 

B) If internal monitoring is required 

C) If 10% of both the internal and external dose 

limits have been exceeded by the end of the 

year based on whole body counts and TLD 

readings 

D) If it is likely that individuals will exceed 

10% of both the applicable internal and 

external limits 

E) If both internal hazards are present in 

excess of 10 times, the ALI and external 

hazards are present capable of exceeding 10 

times the annual limit in one hour 


The assessment of summation should be done prior to exposure, not 

after the fact based on whole body counts and TLD readings.

According to 10 CFR 20 the definition of special nuclear material 

includes: 

A) Plutonium 

B) Uranium 233 

C) Uranium enriched in U233 

D) Uranium enriched in U235 



(10 CFR 20)

According to 10 CFR 20, the quality factor for thermal neutrons 

is: 

A) 1 

B) 2 

C) 2.5 

D) 3 

E) 5 


(10 CFR 20)

According to 10 CFR 20, how often does the radiation protection 

program have to be reviewed? 

A) annually 

B) every 2 years 

C) every 3 years 

D) continuously 

E) only once after implementation or after significant change to 

the program 


(10 CFR 20)

For every short lived radionuclides (< 2 hours) suspended in air, 

the external dose may exceed the internal dose by a factor of: 

A) 1 - 1,000 

B) 1 - 100 

C) 1 - 10 

D) 1 

E) >1 


This value comes from Appendix B footnotes of 10 CFR 20.

You work at a nuclear power plant, it is the evening shift and 

you are approached by an NRC inspector who wants to know the 

density thickness of paper protective clothing he observed on a 

worker. He would like the information by the end of the shift. 

Choose the best response. 

A) Politely tell the inspector that he will have 

to wait until you call the manufacturer 

tomorrow 

B) Call site Security and tell them you think 

you smelled alcohol on the inspector's breath 

C) Call the company ombudsman at home and ask 

what you should do 

D) Cut out a square piece of material, send it 

to the chemistry lab to be weighed and divide 

the weight by the area of the material 

E) Obtain a beta source of known activity and 

energy, count the source without shielding, 

then insert pieces of protective clothing 

material between the source and the detector 

until the counts fall off to background. 

Divide the maximum range, in mg/cm^2, of the 

beta source by the number of layers of 

protective clothing needed to totally shield 

the source. 


Answer B is more fun and answer E is more work. The answer in D 

will yield units of g/cm^2 or mg/cm^2 which is density thickness.

The internal hazard from uranium at an enrichment facility is in 

general: 

A) constant regardless of enrichment 

B) based only on chemical toxicity 

C) based on chemical toxicity at low enrichments 

and radiation effects at higher enrichments 

D) based only on radiation effects at low 

enrichments and critcality at higher 

enrichments 

E) based on radiation effects at low enrichments 

and chemical toxicity at higher enrichments 


Uranium is primarily a chemical toxicity hazard until 

concentration produces a criticality hazard.

A safe geometry to prevent criticality accidents would be one 

that includes which of the following conditions? 

A) A geometry that maximizes the surface area to 

volume ratio 

B) A geometry that minimizes surface area to 

volume ratio 

C) A geometry that maximizes the presence of a 

moderator 

D) A geometry that maximizes the volume to 

surface ratio 

E) A geometry that maximizes the presence of a 

reflector 


This configuration allows maximum neutron escape from the fissile 

mass, thereby reducing the possibility of criticality.

Which of the following is NOT true concerning uranium fires? 

A) Machine turning and filings of uranium tend 

to be pyrophoric 

B) C02 has been shown to be most effective in 

fighting a uranium fire 

C) Halon may be explosive is directed at burning 

uranium 

D) Immersing burning uranium in water may 

dissociate hydrogen and oxygen, supplying 

fuel for the fire 

E) Uranium fires can be smothered by a mixture 

of sodium cloride and potassium carbonate 


C02 is not effective in fighting a uranium fire. All of the 

others are true. A uranium fire immersed in water may eventually 

extinguish the fire, provided enough water is present to account 

for water being boiled away.

Which of the following bioassay methods may be found in a uranium 

facility? 

A) In-vivo monitoring using sodium iodide 

detectors 

B) In-vivo monitoring using hyperpure germanium 

detectors 

C) In-vivo monitoring using phoswich detectors 

D) In-vitro monitoring using urinanalysis and 

fecal analysis 



X-rays and gamma emmisions from U-235 and U-238 daughters can be 

detected as low as 1 nCi with state of the art systems.

The most plausible explanation for the increasing frequency of 

detection of "hot particles" at nuclear power plants is: 

A) the increased use of more sensitive 

instrumentation for detecting and measuring 

contamination by these particles 

B) an increase in the rate of production of 

these particles at nuclear power plants 

C) the changes in plant chemistry that have 

enhanced fuel reliability but have increased 

the corrosion rate of other components 

D) a decrease in the average corrosion particle 

size as plants have aged 

E) the trend toward increasing the time between 

refueling outages with a subsequent decrease 

in preventive maintenance 


More sophisticated portal, hand and foot, and laundry monitors 

with high sensitivity have had a significant effect on hot 

particle detection.

Radiobiological evidence suggests that, when compared to more 

uniform irradiation by the same quantity of radioactive material, 

highly localized beta irradiation of the skin, such as from a hot 

particle on the skin: 

A) is less likely to cause skin cancer 

B) is more likely to cause skin cancer 

C) is about equally likely to cause skin cancer 

D) is likely to cause erythema within a few 

hours 

E) is likely to cause a small necrotic lesion on 

the skin of an individual after only a few 

hours of exposure 


Localized activity produces high doses to a relatively small 

number of nearby cells, resulting in cell death. Uniform 

irradiation is likely to damage a larger number of cells without 

killing them, thus increasing the probability of the occurrence 

of cancer.

Which of the following statements is NOT correct with regard to 

the administration of KI to off-site radiological survey team 

members? 

A) Some people can have an allergic reaction to 

KI 

B) KI must be given before the intake starts to 

have a beneficial effect 

C) KI has a definite shelf life 

D) People who eat seafood regularly may already 

have their thyroid saturated with iodine 

E) The risks of administering KI must be 

carefully balanced with the benefits of its 

use 


According to the FDA, to have the greatest effect in decreasing 

the accumulation of radioiodine in the thyroid gland, potassium 

iodide (KI) should be administered immediately before or after 

exposure. 

(See "The Health Physics and Radiological Health Handbook", 

Revised Edition, Scinta, Inc., edited by B. Schleien)

The "planned special exposure" provision in 10 CFR 20 is to be 

used under what circumstances? 

A) For personnel overexposures after they occur 

B) Whenever the licensee wants to keep an 

individual's routine exposure low 

C) Whenever the licensee requires additional 

allowable exposure for a worker 

D) Only in emergency situations 

E) Only in exceptional situations where 

alternatives are unavailable or impractical 


Planned special exposures (PSEs) are not to be used for routine 

dose extensions or on-the-spot dose extensions under emergency 

conditions. Specific requirements can be found in 10 CFR 

20.1206. Regulatory Guide 8.35 further clarifies the use of 

PSEs.

10 CFR 20 exposure limits for minors are based on what percentage 

of the adult occupational limits? 

A) 5% 

B) 10% 

C) 15% 

D) 20% 

E) 25% 


See 10 CFR 20.1207

A female radiation worker declares to her supervisor that she is 

pregnant. It is determined that the embryo/fetus has already 

received 700 mrem at the time the worker declares her pregnancy. 

According to 10 CFR 20, how much additional dose equivalent may 

the embryo/fetus receive during the remainder of the pregnancy? 

A) No additional dose equivalent is allowed 

B) 300 mrem 

C) 4.3 rem 

D) 50 mrem 

E) 550 mrem 


10 CFR 20 limits the dose to an embryo/fetus to 500 mrem for the 

entire gestation period. 20.1208 allows an additional 50 mrem 

dose equivalent to the embryo/fetus for the remainder of the 

pregnancy if the embryo/fetus has received more than 450 mrem at 

the time of the declaration of pregnancy. Keep in mind that the 

female worker must still not exceed her annual dose equivalent 

limits.

Which of the following is the 10 CFR 20 definition of a Very High 

Radiation Area (VHRA)? 

A) An area, accessible to individuals, in which 

the radiation levels could result in an 

individual receiving an absorbed dose in 

excess of 50 rads (0.5 grays) in 1 hour at 1 

meter from a radiation source or any surface 

that the radiation penetrates 

B) An area, accessible to individuals, in which 



excess of 5,000 rads (50 grays) in 1 hour at 

1 meter from the radiation source or any 

surface that the radiation penetrates 

C) An area, accessible to individuals, in which 



excess of 5,000 rads (50 grays) in 1 hour at 

30 centimeters from the radiation source or 

any surface that the radiation penetrates 

D) An area, accessible to individuals, in which 



excess of 500 rads (5 grays) in 1 hour at 1 

meter from the radiation source or any 

surface the radiation penetrates 

E) An area, accessible to individuals, in which 

the radiation levels could cause an 

individual to receive an absorbed dose in 

excess of 500 rads (5 grays) in 1 hour at 30 

centimeters from the radiation source or any 

surface the radiation penetrates 


VHRA is defined in 10 CFR 20.1003

The iodine isotope that would deliver the largest dose to the 

thyroid of an individual exposed to an accidental release from a 

nuclear power reactor is: 

A) I-129 

B) I-130 

C) I-131 

D) I-132 

E) I-133 


I-131 has a much longer half-life (8.05 d) than all of the 

isotopes listed, with the exception of I-129 (1.57E7 yr). 

However, I-129's fission yield (0.75% from U-235) is much lower 

than than I-131's (2.89%). Additionally, I-131 emits a much more 

energetic beta (0.606 MeV) than I-129 (0.15 MeV).

10 CFR 20 requires a radiation area to be posted if: 

A) the dose rate at 1 meter from the source 

of radiation exceeds 5 mrem/hr 

B) an individual could exceed a dose equivalent 

in excess of 5 mrem in 1 hour or 100 mrem in 

5 days 

C) an individual could exceed a dose equivalent 

in excess of 5 mrem in 1 hour at 1 meter from 

the source of radiation 

D) an individual could exceed a dose equivalent 

in excess of 5 mrem in 1 hour at 30 cm from 

the source of radiation 

E) the dose rate at 30 cm from the source of 

radiation exceeds 5 mrem/hour 


Defined in 10 CFR 20.1003

A Type A quantity of radioactive materials in a package labeled 

"Yellow-II" is exempt from the 10 CFR 20 radiation and 

contamination receipt survey requirements if it contains: 

A) only nuclides with half-lives < 30 days 

B) only gases or special form materials 

C) < 10 mCi of H-3, C-14, S-35, or I-125 

D) less than 10 uCi of radioactive material 

E) there are no exemptions from the receipt 

survey requirements for labeled packages of 

radioactive materials 


10 CFR 20.1906(b)

All of the following, with one exception, have been reported to 

be useful in monitoring the performance of the radiation 

protection program at a nuclear power plant. That exception is: 

A) number of Certified Health Physicists on the 

staff 

B) collecive exposure 

C) incidence of skin/clothing contamination 

D) solid radwaste volume 

E) radiological incident reports 


All other choices are quantifiable indicators of the 

effectiveness of a facility RP program.

When working with liquid solutions containing radioactivity, all 

of the following are appropriate for contamination control 

EXCEPT: 

A) in order to assure ease of cleanup, surfaces 

in the area should be made of materials that 

are easily cleaned 

B) sinks and drains for radioactive liquid 

should be provided 

C) holding and sampling tanks should be used to 

prevent the release of liquids with high 

concentrations of radioactivity 

D) spills should be cleaned up using absorbent 

material and cleaning from the center of the 

spill to its periphery 

E) processing or other removal systems should be 

used to the maximum extent practical 


Spills should be cleaned starting at the outer edges and moving 

toward the center. All other choices are valid contamination 

control practices.

N-13, Ar-41, Kr-87, Kr-89, Xe-135, and Xe-137 are gaseous 

radioactive wastes resulting from which one of the following 

phases of the nuclear fuel cycle? 

A) mining and milling 

B) refining 

C) fuel fabrication 

D) reactor operation 

E) chemical processing 


N-13 and Ar-41 are air activation products. The kryptons and 

xenons are fission products. Of all choices, only reactor 

operation includes these short-lived fission products.

At a nuclear power reactor facility, which is the MOST important 

aspect of a respiratory protection program for limiting internal 

radiation dose? 

A) an adequate testing, fitting, and training 

program 

B) an adequate whole body counting program to 

ascertain that equipment is providing its 

reported degree of protection 

C) an adequate urinalysis program 

D) requiring nose wipes of all individuals to 

ascertain that equipment is actually working 

E) requiring, as a minimum, the use of 

particulate filter type respirators for all 

individuals entering the containment 


NRC's NUREG 0041 addresses the elements of an effective 

respiratory protection program. It is important to verify that 

all devices used are capable of providing the rated protection 

factor for each individual wearing the device. It is also 

important that all individuals are trained in the proper use of 

each device, since the use of respiratory protection in itself 

presents a significant risk to the wearer. Respiratory 

protection should only be used after removal of the source and 

other engineering controls have been considered.

Reference Man's air inhalation under conditions of light activity 

for an eight-hour period is approximately: 

A) 1 E6 cc 

B) 1 E7 cc 

C) 3 E7 cc 

D) 5 E7 cc 

E) 1 E8 cc 


ICRP 23 specifies Reference Man's breathing rate as about 2 E4 

ml/min. So, 

(2 E4 ml/min)(60 min/hr)(8 hr)(1 cc/ml) = 9.6 E6 cc 

= approx. 1 E7 cc

Doses to the thyroid and whole body used for the purpose of 

calculation of distance factors for power and test reactors are 

respectively: 

A) 300 rem and 25 rem 

B) 200 rem and 15 rem 

C) 100 rem and 10 rem 

D) 50 rem and 5 rem 

E) 10 rem and 1 rem 


These limits are specified in 10 CFR Part 100, "Reactor Site 

Criteria." The Exclusion Radius is the radius from the release 

point where these limits would be exceeded in 2 hours following 

the onset of a postulated worst-case release. The Low Population 

Zone is defined for the entire duration of the release.

Respiratory Protection Factors for airborne radioactive material 

are found in: 

A) 10 CFR 20.101 

B) 10 CFR 20 Appendix A 

C) 10 CFR 20 Appendix B 

D) 10 CFR 20 Appendix C 

E) 10 CFR 19.13 


Appendix B lists derived air concentrations (DACs) and annual 

limits on intake (ALIs). Appendix C lists quantities of licensed 

materials requiring labeling. 10 CFR 19 contains required 

notices to workers.

The term "reference man" in health physics is: 

A) the mathematically correct human being with 

organs which are defined by spheroids and 

ellipsoids to make a technically correct body 

for dosimetry evaluations 

B) the phantom which is used to reference a body 

counter to a standard 

C) a set of agreed upon values for the many 

characteristics of the human body which are 

needed for internal dose evaluations 

D) a man of large stature to ensure conservative 

interpretation of dose to any individual 

E) a set of agreed upon values for exposure 

times and rates that the normal human could 

tolerate 


The anatomical characteristics of Reference Man are listed in 

ICRP Publication 23.

A full-face respirator with HEPA filters is always recommended 

for typical reactor noble gas atmospheres because: 

A) the radioactive noble gas progeny must be 

filtered out 

B) the beta dose to the lens of the eye will be 

greatly reduced 

C) the probability of a skin contamination will 

be minimized 

D) this type of full face respirator is not 

recommended for noble gas atmospheres 

E) this type of respirator offers the highest 

protection factor in noble gas atmospheres 


An air-purifying respirator will not provide protection against 

noble gases, only their particulate progeny. Radioactive noble 

gases tend to be most limiting from an external exposure 

standpoint.

According to 10 CFR 20 Appendix A, a positive pressure, full 

face, air-purifying respirator has a maximum protection factor 

for particulates of: 

A) 10 

B) 50 

C) 100 

D) 1,000 

E) 2,000 


The full-face, positive pressure, air-purifying respirator is 

assigned a protection factor of 1,000 for particulate 

radionuclides. 

(See 10 CFR 20 Appendix A)

In the transportation of radioactive materials, the PRIMARY means 

of achieving safety is: 

A) effective use of time, distance, and 

shielding by everyone involved 

B) restricting transport to times of low traffic 

density 

C) proper approved packaging for the contents 

D) use of placards and labels that contain 

warnings 

E) proper procedures to prevent damage from 

rough handling 


The package is the primary engineering barrier between the 

hazardous material and personnel. Packaging is designed to 

withstand various degrees of transportation conditions. Type A 

packaging is designed to withstand normal conditions of 

transport. Type B packaging is designed to withstand 

hypothetical accident conditions.

The Radioactive Yellow II and III labels for packages of 

radioactive materials must contain the "transport index". The 

transport index is a measure of the: 

A) dose equivalent rate at one meter from the 

package surface 

B) dose equivalent rate at one foot from the 


C) dose equivalent rate on contact with the 


D) number of curies in the package 

E) total mass of radioactive material in the 

package 


The transport index is written in the "TI" box on the Radioactive 

Yellow II and III labels. In addition to the package surface 

radiation level, the TI determines the type of label to be 

applied to the package.

The dose equivalent rate at the surface of a package is 180 

mrem/hr. The label required for shipment is: 

A) Radioactive White I 

B) Radioactive Yellow II 

C) Radioactive Yellow III 

D) Radiation Area 

E) High Radiation Area 


A Radioactive Yellow III label must be applied to any package of 

radioactive material not excepted from labeling that has a 

surface radiation level greater than 50 mrem/hr or a transport 

index greater than 1.0.

For an exclusive use, closed transport shipment of a radioactive 

materials package, at what level does external package removable 

beta/gamma contamination become unacceptable upon arrival at the 

consignee's facility? 

A) 10^-6 uCi/cm^2 

B) 10^-5 uCi/cm^2 

C) 10^-4 uCi/cm^2 

D) 10^-3 uCi/cm^2 

E) 10^-2 uCi/cm^2 


49 CFR 173 allows package removable surface contamination levels 

of up to 100 times the normal limits upon arrival at the 

consignee's location if the package is transported exclusive use, 

closed transport.

Based on the following DOT/NRC "A" values for the normal form of 

each isotope, which isotope is considered to exhibit the highest 

radiotoxicity? 

A) Co-60, 10.8 Ci 

B) Cs-137, 13.5 Ci 

C) Cf-252, 2.7E-2 Ci 

D) C-14, 54.1 Ci 

E) Cm-242, 0.27 Ci 


The "A" value represents the maximum quantity of a particular 

radionuclide that may be shipped in a Type A container. 

Quantities exceeding this value must generally be shipped in a 

Type B container. The lower the "A" value, the higher the 

radiotoxicity.

Which of the following regulations exclusively addresses the 

medical use of byproduct materials? 

A) 10 CFR 19 

B) 10 CFR 20 

C) 10 CFR 34 

D) 10 CFR 35 

E) 10 CFR 71 


10 CFR Part 19 deals with notices and instructions to workers, 

Part 20 covers protection from ionizing radiation, Part 34 covers 

industrial radiography, and Part 20 is the NRC's transportation 

rule.

In NTE (nuclear track emulsion) film, the tracks are caused by: 

A) alpha particles 

B) beta particles 

C) gamma photons 

D) recoil neutrons 

E) recoil protons 


In this fast neutron responsive dosimeter, recoil protons from 

elastic scattering with hydrgen atoms in the film create short 

"tracks" of ionization as stable silver atoms are created. Thes 

tracks are counted either by eye or mechanically and equated to 

total neutron dose equivalent.

The sensitivity of photographic film to photons is energy 

dependent primarily because of: 

A) varying conditions of temperature and 

humidity during exposure 

B) strong photoelectric absorption by the silver 

bromide in the emulsion 

C) varying energies of the Compton-scattered 

photons 

D) pair production 

E) build-up 


Film is considered to be "energy dependent" since it is most 

efficient for photon detection when interaction is by 

photoelectric effect. As we know, photoelectric effect 

predominates only below 200 keV. This is one reason that filters 

are used in film badges.

What is the effective half-life in the human body for Cobalt-60, 

if the biological half-life is eight days? 

A) 0.125 days 

B) 1.52 days 

C) 7.97 days 

D) 45.8 days 

E) 1.52 years 


A good thumb rule for calculating effective half-life is that if 

the isotope has a half-life greater than 100 days, the effective 

half-life (Teff) is only a bit less than the biological 

half-life. The effective half-life is never greater than the 

biological half-life. The equation to calculate Teff is as 

follows: 

Teff = Tb x Tr / Tb + Tr 

where: Tb = biological half-life 

Tr = radiological (physical) half-life

If the DAC for Rn-222 is 3.0 E-8 microcuries/ml, the working 

level is: 

A) 9.0 E-8 microcuries/ml 

B) 9.0 E-9 microcuries/ml 

C) 3.0 E-9 microcuries/ml 

D) 6.0 E-7 microcuries/ml 

E) 6.0 E-8 microcuries/ml 


According to 10 CFR 20 Appendix B, the DAC for Rn-222 is 1/3 of 

the working level.

An individual who receives 40 DAC-hours will receive a committed 

effective dose equivalent of: 

A) 10 millirem 

B) 40 millirem 

C) 80 millirem 

D) 100 millirem 

E) 1250 millirem 


Assuming the DAC is based upon the sALI, one DAC-hour is equal to 

a CEDE of 2.5 mrem. So: 

40 DAC-hrs x 2.5 mrem/DAC-hr = 100 mrem

The full width at half maximum peak energy for a Cesium-137 

photopeak using a GeLi detector is 3 keV. The photopeak energy 

is 0.662 MeV. The percent resolution of the detection system for 

this energy is: 

A) 0.22% 

B) 0.45% 

C) 4.53% 

D) 22.0% 

E) 45.3% 


% resolution = (FWHM/peak energy) x 100% 

= (3 keV/662 keV) x 100% 

= .453 %

What is the main advantage of using a proportional counter? 

A) It operates in a higher voltage region 

B) It is able to differentiate between different 

types of radiation 

C) It causes significantly more free electrons 

D) It is less energy dependent than other 

detectors 

E) It possesses higher sensitivity than other 

detectors 


In the proportional region, radiations with different specific 

ionization create pulses of different heights. By using pulse 

height discriminators, alpha can be distinguished from beta-gamma 

pulses.

What are the constituents of the fill gas P-10? 

A) 10% argon and 90% methane 

B) 50% argon and 50% methane 

C) 90% argon and 10% methane 

D) 60% argon and 10% methane 

E) 10% argon and 60% methane 


P-10 is used in gas-filled detectors in the proportional and G-M 

regions. The argon serves as the ionization gas, the methane is 

an organic quench gas.

You are setting up a count room for analysis of airborne and 

surface contamination samples at a facility where the isotopes of 

concern are transuranics, fission products, and activation 

products. Your BEST selection of instruments would be: 

A) Geiger-Mueller detector with scaler, zinc 

sulfide scintillation detector 

B) Geiger-Mueller detector with scaler, GeLi 

detector 

C) gas flow proportional counter, GeLi detector 

D) zinc sulfide scintillation detector, GeLi 

detector 

E) sodium iodide scintillation detector, gas 

flow proportional counter 


Since the isotopes of concern are emitting alpha, beta, and gamma 

radiations, a proportional counter will be necessary for its 

capability to distinguish between alpha and beta-gamma. Since 

airborne contamination is being measured, gamma spectroscopy 

capability (in this case GeLi has the best resolution) is 

required to identify radionuclides having different DACs.

A meter reads 40,000 net cpm and the efficiency of the detector 

is 40%. How many dpm does this represent? 

A) 10,000 dpm 

B) 16,000 dpm 

C) 10,000 dpm 

D) 100,000 dpm 

E) 1,000,000 dpm 


activity(dpm) = count rate(cpm)/efficiency 

= 40,000 cpm/.40 

= 100,000 dpm

Why is a NaI(Tl) detector housed in a cannister? 

A) to prevent beta particle interference in the 

detector 

B) to minimize Compton scattering in the 

detector 

C) to keep the detector dry due to its 

hygroscopic characteristics 

D) to promote bremsstrahlung for maximum 

efficiency 

E) to prevent cosmic radiation interference in 

the detector 


Sodium Iodide will absorb moisture if left open to the 

atmosphere. This will cause detector decomposition and reduction 

in visible light transmission.

According to ANSI N323-1978, portable linear readout radiation 

detection instruments should be calibrated: 

A) at 50% of each scale to within +/- 10% of 

known radiation values 

B) at 20% and 80% of each scale to within +/- 

10% of known radiation values 

C) at 20%, 50%, and 80% of each scale to within 

+/- 20% of known radiation values 

D) at 50% of each scale to within +/- 20% of 


E) at 80% of each scale to within +/- 20% of 



The calibration should then be checked at 50% of each scale to be 

used. Specifications for response are addressed in ANSI 

N42.17A-1989.

For in-vivo bioassay of a mixture of gamma-emitting 

radionuclidess, the best detector is: 

A) large geometry gas-flow proportional 

B) Na I 

C) GeLi 

D) SiLi 

E) external liquid scintillation 


Since a mixture of radionuclides is specified, the detector with 

the best resolution is probably the "best".

Common radionuclides used for the calibration of portable gamma 

photon detectors include: 

A) Co-60, Cs-137, Ar-41 

B) Co-60, Cs-137, Rn-222 

C) Co-60, Cs-137, Ra-226 

D) Cs-134, Cs-137, Ra-226 

E) Co-60, Cs-134, Kr-85 


Of the three, Radium is not used very frequently, although it was 

at one time. Sealed radium sources are susceptible to rupture 

due to buildup of radon gas.

A detection system records 22 counts during a one minute counting 

period. How should the results be expressed to one standard 

deviation? 

A) 11 +/- 1.1 cpm 

B) 11 +/- 2.2 cpm 

C) 22 +/- 4.7 cpm 

D) 22 +/- 1.1 cpm 

E) 22 +/- 5.1 cpm 


One standard deviation (1 sigma) represents the 68% confidence 

level. For this problem, it is calculated as follows: 

1 sigma = (sample count rate/sample count time)^1/2 

= ( 22/1 )^1/2 

= +/- 4.69

How long must a sample with a count rate of 250 cpm be counted to 

give a total count rate standard deviation of 1%? 

A) 4 minutes 

B) 20 minutes 

C) 40 minutes 

D) 100 minutes 

E) 400 minutes 


Since 

1 sigma = (sample count rate/sample count time)^1/2 

and 

1 sigma = (.01)x(250 cpm) 

then 

(.01)x(250) = (250/sample count time)^1/2 

and 

2.5 = (250/sample count time)^1/2 

and 

(2.5)^2 = 250/sample count time 

so 

40 = sample count time

You determine the background of a proportional counter by 

measuring 35 counts in a period of 45 minutes and conclude the 

background count rate to be 0.78 cpm. What is the estimated 

standard deviation of this background count rate? 

A) 0.13 cpm 

B) 0.27 cpm 

C) 0.3 cpm 

D) 1.0 cpm 

E) 6 cpm 


1 sigma = (count rate/count time)^1/2 

= (.78 cpm/45 m)^1/2 

= +/- 0.13 cpm

Quality factor is a function of the: 

A) collision stopping power of the radiation in 

water 

B) collision stopping power of the radiation in 

any absorber 

C) attenuation of the radiation in the air 

D) absorption of the radiation by any absorber 

E) attenuation of the radiation in any absorber 


Quality factor is represented in ICRP Publication 26 (1977) as a 

function of the collision stopping power of the radiation in 

water. It has been replaced with the concept of radiation 

weighting factor in ICRP Publication 60 (1990).

The quality factor refers to all of the following except: 

A) the factor relating absorbed dose (rads) to 

dose eqivalent (rems) 

B) for all radiation sources, the constant 

factor which relates absorbed dose to dose 

equivalent 

C) the factor that depends on linear energy 

transfer (LET) 

D) the factor which is greater for higher LET 

radiation than for lower LET radiation 

E) the factor which depends on the 

characteristics of secondary charged 

particles liberated by the interaction of 

indirectly ionizing radiation in tissue 


As defined in ICRP Publication 26 (1977), quality factor varies 

for different types of radiation depending upon the LET, thus, is 

not constant for all radiation sources.

A proper average quality factor for estimating the dose 

equivalent in a radiation field consisting of an unknown spectrum 

of fast neutrons is: 

A) 1 

B) 5 

C) 8 

D) 10 

E) 15 


10 is the quality factor for neutrons of unknown energies, as 

represented in ICRP Publication 26 (1977) and 10 CFR Part 20 

(revised 1991).

At what radius would you post a radiation area around a ten curie 

Manganese-54 (.835 MeV gamma) point source? (Assume 1 

photon/disintegration.) 

A) 70 feet 

B) 81 feet 

C) 95 feet 

D) 101 feet 

E) 145 feet 


According to 10 CFR Part 20, a radiation area is an area where an 

individual could exceed a deep dose equivalent of 5 mrem in one 

hour at 30 cm from the source. Using the inverse square law: 

R1 (D1)^2 = R2 (D2)^2 

and 

D = 6CEN; 

(6CEN)R/hr x (1)^2 = .005 R/hr x (D2)^2 

50.1 x 1 = .005 x (D2)^2 

10020 = (D2)^2 

(10020)^1/2 

= D2 

100.09 feet = D2

A point source of 137-Cs with an activity of 1 Ci, a photon 

energy of 0.662 MeV, and a photon yield of 0.85 

photons/disintegration is measured at two feet. The expected 

exposure rate is: 

A) 3.38 R per hour 

B) 1.69 R per hour 

C) 0.84 R per hour 

D) 0.99 R per hour 

E) 0.90 R per hour 


Use 6CEN and the inverse square law: 

(6CEN) R/hr x (1)^2 = R2 x (2)^2 

3.3762 R/hr = R2 x 4 

0.844 R/hr = R2

A technician is working three feet from a gamma radiation point 

source. If the technician moves to a second location which is an 

additional three feet from the source, the dose rate to the 

technician will be reduced by a factor of: 

A) 2:1 

B) 4:1 

C) 5:1 

D) 1:3 

E) 3:1 


The reduction factor, employing the inverse square law is 

1/(3)^2 : 1/(6)^2 

which equals 

1/9 : 1/36 

which equals 

4 : 1

An individual breathes a concentration of 2.0 E-8 microcuries per 

milliliter of Cesium-137 for two and one-half hours. If the DAC 

for Cesium-137 is 6.0 E-8 microcuries/milliliter, his approximate 

committed effective dose equivalent will be: 

A) 2 millirem 

B) 12.5 millirem 

C) 17.5 millirem 


E) 27.5 millirem 


One DAC-hour based upon sALI = 2.5 mrem 

and 

DAC fraction x hours = DAC-hours 

so 

(2.0 E-8/6.0 E-8 x 2.5 hrs) x 2.5 mrem/DAC-hr 

= 2.08 mrem

A radiation worker is exposed for a period of four hours to 

airborne radioactivity with a DAC of 1 E-8 microcuries/cc. What 

is the maximum concentration to which he could be exposed for the 

four hour period without exceeding 40 DAC-hours? 

A) 1 E-8 microcuries/cc 

B) 1.3 E-6 microcuries/cc 

C) 1 E-7 microcuries/cc 

D) 5.2 E-6 microcuries/cc 

E) 1.1 E-10 microcuries/cc 


(concentration/DAC) x hours = DAC-hours 

(concentration/1 E-8) x 4 = 40 

concentration/1 E-8 = 10 

concentration = 1 E-7

A person is standing in a semi-infinite cloud of Xenon-133 (0.081 

MeV gamma) with a concentration of 3.0 E-1 microcuries/ml. What 

is the maximum time the person may stay there without exceeding a 

whole body gamma radiation dose of 25 rem? 

A) 4.1 minutes 

B) 24.3 minutes 

C) 68 minutes 

D) 1.5 hours 

E) 2.43 hours 


In a semi-infinite cloud of gamma-emitting noble gases, the gamma 

contribution to the absorbed dose rate (D) can be estimated as: 

D = .25 EX 

where D = rads/sec = rems/sec 

E = gamma energy(MeV) x yield 

x = concentration (uCi/cc) 

and stay time is calculated as: 

stay time = allowable dose/dose rate 

so 

stay time = 25 rem/.25 EX 

= 25 rem/ .25 (.081)(3.0 E-1) 

= 4115 sec x (1 min/60 sec) 

= 68.59 min

A sulphur pellet is sometimes used in a personnel dosimeter. Its 

purpose is to: 

A) measure gamma exposure 

B) measure beta exposure 

C) measure neutron exposure 

D) measure background exposure 

E) measure radon daughter exposure 


Sulfur is used in criticality accident dosimetry. The 

S-32(n,p)P-32 reaction produces measurable beta activity, which 

can be equated to neutron dose equivalent.

Personnel dosimetry records must be retained: 

A) for the period of time it takes for the 

individual to reach 75 years of age 

B) for a period of one year following the 

individual's death 

C) for a period of five years following the 

individual's death 

D) until the NRC terminates the pertinent 

license 

E) for 50 years 


10 CFR Part 20 requires that personnel monitoring records be 

maintained until the NRC license is terminated.

Filters are used in film badges in order to: 

1) accelerate beta particles 

2) correct for tissue equivalence 

3) discriminate between different types of 

radiation 

4) correct for energy dependence of film 

A) 1,2,3 

B) 2,4 

C) 2,3 

D) 2,3,4 

E) 1,2,3,4 


Density thicknesses of filters are adjusted to correspond to 

various required measurement depths in tissue (i.e. shallow, 

lens, eye). "Windows" in the film badge allow for discrimination 

between beta and gamma radiation. Filters are also used to 

"soften" the energy of incident photons to promote photoelectric 

effect in the film, thereby increasing its efficiency.

How is beta exposure determined in a beta-gamma radiation field 

using film dosimetry? 

A) the beta dose is evaluated by subtracting the 

open window film reading from the closed 

window film reading 

B) the beta dose is evaluated by subracting the 

closed window film reading from the open 

window film reading 

C) the beta dose is evaluated by ratioing the 

open window film reading to the closed window 

film reading 

D) the beta dose is evaluated by ratioing the 

closed window film reading to the open window 

film reading 

E) the beta dose is extrapolated from the beta 

to gamma ratio of the radionuclides present 


The open window reading yields beta and gamma effects. The 

closed window reading yields gamma only. So: 

Open - Closed = beta effects

The average activity of Potassium-40 found in the human body is: 

A) 2.22 E 3 disintegrations per minute 

B) 2.22 E 4 disintegrations per minute 

C) 2.22 E 5 disintegrations per minute 

D) 3.70 E 3 disintegrations per minute 

E) 3.70 E 4 disintegrations per minute 


According to ICRP Publication 23, Reference Man contains 100 

nanocuries (1 E-7 curies) of K-40. So: 

1 E-7 Ci x 2.22 E12 dpm/Ci = 2.22 E5 dpm

The major internal pathway for radionulides is: 

A) inhalation 

B) ingestion 

C) activation 

D) absorption 

E) injection 


The most common pathway for internally deposited radionuclides, 

whether the exposures are occupational or environmental 

(non-occupational) is by inhalation.

An intake of one non-stochastic ALI by the specified route will 

result in: 

A) 5 rem committed dose equivalent to a tissue 

or organ 

B) 5 rem committed effective dose equivalent 

C) 50 rem committed dose equivalent to a tissue 

or organ 

D) 50 rem committed effective dose equivalent 

E) 50 rem total effective dose equivalent 


The non-stochastic ALI (nALI) is that amount of radioactive 

material which will produce a 50 year committed dose equivalent 

to an individual organ or tissue of 50 rems. The stochastic ALI 

(sALI) will produce a 50 year committed effective dose equivalent 

of 5 rems.

Which of the following radionuclides is most applicable to 

in-vivo measurements? 

A) H-3 

B) C-14 

C) S-35 

D) I-131 

E) Pu-239 


Since I-131 is the only significant gamma-emitting nuclide shown, 

it is clearly the most applicable to in-vivo measurement. NOTE: 

Pu-239 does emit a weak gamma. All other nuclides shown are 

"pure beta-emitters".

A detector with a resolving time of 100 microseconds yields 

175,000 net counts in one minute. What is the true count rate of 

the sample? 

A) 17,502 cpm 

B) 100,000 cpm 

C) 166,666 cpm 

D) 247,058 cpm 

E) 1,000,327 cpm 


true countrate = 

observed /1-[(observed)x(resolving time)] 

NOTE: Be sure to convert resolving time to same units used in 

expressing count rate. 

So: 

true count rate= 

175,000/1-[(175,000)x(100usec x 1E-6sec/usec x 1min/60sec)] 

= 247,058 cpm

Proportional counters operate at ______ voltages than/as 

ionization chambers. 

A) lower 

B) equal 

C) higher 

D) lower and equal 

E) equal and higher 


In the six region curve for gas-filled detectors, the regions in 

order of increasing voltage (the x-axis) are: 

Recombination, Ionization, Proportional, Limited Proportional, 

Geiger-Mueller, Continuous Discharge

An accurate measurement of exposure rate can be obtained when 

using an air ionization chamber to measure a photon beam smaller 

than the detector, if: 

A) a scattering material is installed between 

the beam and the detector 

B) the beam conversion factor for the instrument 

is used 

C) the beam is collimated using a high-Z 

material 

D) the detector fill gas pressure is increased 

E) the voltage to the detector is increased 

slightly 


Since the small beam would not produce as much ionization in the 

detector as a field as wide as the detector would, the meter 

would underrespond. This can be corrected with a beam conversion 

factor, if the diameter of the beam is known.

The sensitivity of a pressurized ion chamber for the detection of 

photons can be increased by: 

A) increasing the appled voltage to the ion 

chamber 

B) increasing the ion chamber fill gas pressure 

C) decreasing the applied voltage to the ion 

chamber 

D) decreasing the ion chamber gas pressure 



As pressure is increased, density of the fill gas is increased. 

Since more gas molecules are available for ionization at this 

higher pressure, the chamber is more sensitive.

Which of the following combinations of instruments would be MOST 

effective to establish dose equivalent rates in a mixed neutron 

and gamma radiation field? 

A) air ionization chamber survey meter and 

tissue equivalent boron trifluoride counter 

B) extendable Geiger-Mueller survey meter and 

tissue equivalent boron trifluoride counter 

C) air ionization chamber survey meter and gas 

flow proportional counter 

D) extendable Geiger-Mueller survey meter and 

gas flow proportional counter 

E) air ionization chamber survey and zinc 

sulfide scintillation detector 


For gamma, since "air dose" is nearly equal to deep dose 

equivalent (1 Roentgen = .98 rem), an air ionization chamber 

would be best for gamma. Obviously, a tissue equivalent neutron 

detector (the BF3) is the best instrument given for neutron dose 

equivalent measurement.

If 100 counts are recorded with a detector in one minute, and the 

efficiency of detection is 0.35 counts/disintegration, then the 

activity of the source is: 

A) 4.50 E-5 microcuries 

B) 1.29 E-4 microcuries 

C) 7.72 E-2 microcuries 

D) 2.86 E-2 microcuries 

E) 5.36 E-2 microcuries 


Activity (dpm) = count rate (cpm)/efficiency 

= 100/.35 

= 286 dpm x (1 uCi/2.22 E6 dpm) 

= 1.29 E-4 uCi

A positron emitter is counted in a deep well detector. What 

would be the predominant peak(s)? 

A) 0.511 MeV 

B) 1.022 MeV 

C) 0.511 and 1.022 MeV 

D) 1.533 MeV 

E) a positron emitter will not yield a peak in this configuration 


The positrons will annihilate with electrons, creating two .511 

MeV gammas. Although the simultaneous interaction of these 

gammas would produce a sum peak at 1.022 MeV, such interaction is 

improbable.

A tissue-equivalent chamber must: 

A) be inserted into tissue 

B) have walls of the same mean density as tissue 

C) have a mean density of 300 gms/cubic 

centimeter 

D) be used for depth-dose measurements 

E) be used to measure dose rate 


Since the Bragg-Gray principle states that the dose to the 

detector wall is proportional to the dose to the detector cavity 

gas , constructing an ionization chamber wall from a material 

with the same density as tissue will produce a tissue equivalent 

response in the detector.

According to ANSI N323-1978, portable radiation detection 

instrumentation should be calibrated: 

A) after modification or physical alteration 

only 

B) every six months 

C) every six months or after modification or 

physical alteration 

D) annually or after modification or physical 

alteration 

E) annually only 


The standard recommends calibration annually or after 

modification or physical alteration. Do not confuse this with 

INPO good practices or DOE MILSTD, which require semi-annual 

calibration for these instruments.

The full width at half maximum peak energy for a Mn-54 photopeak 

obtained with a Ge(Li) detector is 3 keV. The photopeak energy 

is 0.835 MeV. The percent resolution of the detection system for 

this energy photon is: 

A) 0.90% 

B) 3.59% 

C) 0.36% 

D) 0.23% 

E) 100% 



= (3 keV/835 keV)x 100% 

= 0.359 %

The full width at half maximum peak energy for a typical Ge(Li) 

detector for Cs-137 should be approximately: 

A) 0.3 keV 

B) 3 keV 

C) 30 keV 

D) 5% 

E) 10% 


This is some ten times better resolution than a 3"x3" Sodium 

Iodide detector. Hyperpure Ge detectors achieve even better 

resolution than Ge(Li).

A stack is 5 feet in diameter, the flow rate in the stack is 

43,000 cubic feet per minute, and the sample line is 0.325 inches 

in diameter. What is the proper sample flow rate for isokinetic 

conditions to exist? 

A) 1.26 cubic feet per minute 

B) 3.88 cubic feet per minute 

C) 7.57 cubic feet per minute 

D) 75.69 cubic feet per minute 

E) 232.9 cubic feet per minute 


V1 x (D2)^2 = V2 x (D1)^2 

43,000 cfm x (0.325 in)^2 = V2 x (5 ft x 12 in/ft)^2 

[43,000 x (0.325 in)^2]/(60 in)^2 = V2 

1.26 cfm = V2

A sample yielded 3504 counts for a five minute counting period. 

A background count of ten minutes yielded 220 counts. What is 

the net count rate and the standard deviation of the sample to 

the 95% confidence level? 

A) 3284 +/- 209 cpm 

B) 480.8 +/- 21.9 cpm 

C) 480.8 +/- 116 cpm 

D) 678.8 +/- 24 cpm 

E) 678.8 +/- 26 cpm 


net count rate = samplerate - bkgrate 

and 

2 sigma = 

1.96[(bkgrate/bkgtime)+(samplerate/sampletime)]^1/2 

So 

(3504/5)-(220/10) +/- 1.96[(220/10/10)+(3504/5/5)]^1/2 

678.8 +/- 23.39 cpm

A sample counted for ten minutes resulted in 1000 counts. The 

background count was 250 counts over a 10 minute period. 

Assuming negligible radioactive decay of the sample during 

counting, the net counting rate in counts per minute should be 

reported at the 95% confidence level as: 

A) 750 +/- 35 

B) 75 +/- 7 

C) 75 +/- 10 

D) 75 +/- 3.5 

E) 75 +/- 14 



and 

2 sigma = 


So 

(1000/10)-(250/10)+/-1.96[(250/10/10)+(1000/10/10)]1/2 

75 +/- 6.93 cpm

If the sample plus background is 1600 counts in one minute and 

the background is 900 counts in one minute, the net count is 700 

counts per minute plus or minus ______ counts per minute (1 

standard deviation). 

A) 10 

B) 26.5 

C) 40 

D) 50 

E) 70 


1 sigma = 

[(bkgrate/bkgtime)+(samplerate/sampletime)]^1/2 

= [(900/1)+(1600/1)]^1/2 

= +/- 50 cpm

The purpose of a "chi-squared" test is to: 

A) establish a "knee voltage" for a detector 

B) ensure that the instrument's results lie 

within a normal Gaussian distribution 

C) establish the efficiency of a detector 

circuit 

D) compare the response of an instrument to a 

known standard 

E) calculate the average sample result obtained 

for a quality of radioactive material 


Since radioactive decay is a random process, a series of at least 

20 counts of the same activity standard should yield a normal (or 

Gaussian) distribution of results. A chi-squared test verifies 

this. If the results do not pass this "goodness of fit" check, 

electronic malfunction of the instrument is indicated.

The quality factor for alpha particles and heavy nuclei is: 

A) 1 

B) 10 

C) 5 

D) 20 

E) 2 


According to ICRP Publication 26 (1977) and 10 CFR Part 20, the 

quality factor is 20. ICRP Publication 60 (1990) has replaced 

the concept of quality factor with radiation weighting factor, 

which remains 20 for these high-LET radiations.

A worker is exposed to different radiations at a work site and it 

is determined that he had a dose of 1 rad from fast neutrons, 1 

rad from thermal neutrons, and 2 rad from gamma rays. What is 

the dose equivalent which should be assigned to this worker? 

A) 3 rem 

B) 7 rem 

C) 15 rem 

D) 24 rem 

E) 45 rem 


The appropriate quality factors are as follows: 

Fast neutrons 10 

Thermal neutrons 3 

Gamma 1 

So: 

(1 rad x 10) + (1 rad x 3) + (2 rad x 1) = 15 rem

Body tissue is exposed to 20 millirad per hour alpha radiation 

for 75 minutes. The dose equivalent to the exposed tissue would 

be about: 

A) 0.25 rem 

B) 0.5 rem 

C) 0.75 rem 

D) 1 rem 

E) 1.25 rem 


rads x QF = rems 

(20 mrad/hr x 75 min x 1 hr/60 min) x 20 = 500 mrem 

= 0.5 rem

Assuming a maximum permissible dose of 100 mrem, what would be 

the allowable working time in a radiation field consisting of 25 

mrad/hr gamma, 50 mrad/hr thermal neutrons, and 15 mrad/hr fast 

neutrons? 

A) 9 minutes 

B) 18 minutes 

C) 27 minutes 

D) 45 minutes 

E) 67 minutes 


Appropriate quality factors are as follows: 

Gamma 1 



and 

Stay time = allowable dose/dose rate 

So 

Stay time = 100 mrem/[(25 x 1)+(50 x 3)+(15 x 10)]mr/h 

= .3077 h 

= 18.46 min

A ten foot long pipe containing Cobalt-60 creates an exposure 

rate of 20 mR/hr at twenty feet. What is the exposure rate at 

one foot from this pipe? 

A) 0.8 R/hr 

B) 1.3 R/hr 

C) 1.6 R/hr 

D) 1.9 R/hr 

E) 2.1 R/hr 


L = 10 feet 

L/2 = 5 feet 

Inside L/2: 

R1(D1) = R2(D2) 

Outside L/2: 

R1(D1)^2 = R2(D2)^2 

So calculate in to L/2 

20 mR/hr (20)^2 = R2 (5)^2 

R2 at L/2 = 320 mR/hr 

Then calculate in to one foot 

320 mR/hr (5) = R2 (1) 

1600 mR/hr = R2 

1.6 R/hr = R2

You measure the dose rate at a job site and determine that a 

worker would receive a dose of 50 millirem by staying at that 

location for 15 minutes. The worker decides to use a long tool 

which makes his distance from the point source three times as 

far, but the work time is increased to 25 minutes. How much dose 

is saved using the long tool? 


B) 0 millirem 





Dose without tool = 50 mrem 

Dose with tool = [50 mrem/(3)^2] x (25 min/15 min) 

= 9.26 mrem 

Dose saved = (50 - 9.26) mrem 

= 40.74 mrem

The exposure rate from a 2 Ci source of Co-60, which emits two 

photons 100% of the time with energies of 1.17 MeV and 1.33 MeV 

is measured at 1 foot. The exposure rate is: 

A) 16 R/hr 

B) 14 R/hr 

C) 5 R/hr 

D) 30 R/hr 

E) 15 R/hr 


D = 6CEN 

= 6{(2)[(1.17 x 1.00)+(1.33 x 1.00)]} R/hr 

= 30 R/hr

The exposure rate from a point source is 5 R/hr at 2 feet. The 

expected exposure rate at 4 feet is: 

A) 1.00 R/hr 

B) 1.25 R/hr 

C) 2.5 R/hr 

D) 10 R/hr 

E) 20 R/hr 


Use the inverse square law: 

5 R/hr (2)^2 = R2 (4)^2 

1.25 R/hr = R2

A worker spends 45 minutes in a room with an Iodine-131 

concentration of 5.0 E-8 microcuries/ml. He is wearing a full 

plastic suit and a full-face negative pressure respirator. If 

the DAC for Iodine-131 is 2.0 E-8 microcuries per milliliter, how 

many DAC hours should the worker be assigned? 

A) 0.25 DAC hours 

B) 2.0 DAC hours 

C) 5.5 DAC hours 

D) 0.1 DAC hours 

E) 0.05 DAC hours 


Since the protection factor of the device is 1 for I-131, the 

calculation is as follows: 

DAC fraction x time(hrs) = DAC-hours 

(5.0 E-8/2.0 E-8) x [45 min x (1 hr/60 min)] 

= 1.875 DAC-hrs

According to the ICRP, "ALI" stands for: 

A) allowable limit of isotopes 

B) allowable limit on intake 

C) annual limit of isotopes 

D) annual limit on intake 

E) accumulated limit of intake 


The ALI is defined in ICRP Publications 26 and 30 (1977). 

Publication 30 gives the actual values for all radionuclides.

The ICRP recommended in 1977 that the total effective dose 

equivalent should not exceed 5 rem in a year. If an individual 

breated 0.2 DAC air for forty hours per week for one year and 

received no other internal expsoure, what is the maximum external 

occupational exposure he could receive under this recommendation? 

A) 2.8 rem 

B) 3.2 rem 

C) 3.9 rem 

D) 4.2 rem 

E) 5.0 rem 


Since breathing one DAC for an occupational year (2000 hours) 

would result in 5 rem CEDE, breathing 0.2 DAC would result in 

5 rem x 0.2 = 1.0 rem 

If 1 rem is being received internally, 4 rem would be allowed 

externally. The best answer is 3.9 rem.

What happens to the noble gases after they are inhaled? 

A) it takes a long time to eliminate them 

through the decay process 

B) they do not remain inside the body 

C) they remain inside the body 

D) it takes a very short time for them to decay 

and be eliminated 

E) they are absorbed by the body and excreted 


The nature of noble (or inert) gases is that they will not 

chemically bind with other elements. Therefore, they do not 

remain inside the body. They pose more of an external than 

internal radiation hazard, and require the calculation of 

"submersion dose". In fact, the DACs for the radioactive noble 

gases are based upon external exposure.

The specific gamma constant of a particular radionuclide emitting 

3 MeV photons is 1 R/hr per curie at 1 m. The exposure rate at 

10 cm from a point source of 10 curies is approximately: 

A) 10 R/hr 

B) 100 R/hr 

C) 1000 R/hr 

D) 3000 R/hr 

E) 5000 R/hr 


In this calculation, curie content is being increased by a factor 

of 10, and distance decreased by a factor of 10. This results in 

a total increase in exposure rate of: 

10 x (10)^2 = 1000 

So 

1 R/hr x 1000 = 1000 R/hr

The detection of radioactive tritium in an air sample is best 

accomplished with: 

A) a liquid scintillation counter 

B) a thin 7 mg/cm2 end window proportional 

counter 

C) a GM detector 

D) an internal ionization chamber 

E) a gas flow detector having a window 

sufficiently thin to detect alpha radiation 


Tritium (H-3) is a "pure beta-emitter" with an endpoint energy 

(Emax) of 18.6 keV. This energy is so low that the sample must 

actually be immersed in the detector material, which is the 

principle behind liquid scintillation counting.

A counting rate of 40 cpm is measured in 2 minutes. What is the 

standard deviation of this counting rate? 

A) +/- 6.3 cpm 

B) +/- 4.5 cpm 

C) +/- 5.0 cpm 

D) +/- 6.0 cpm 

E) +/- 4.7 cpm 


1 sigma = (countrate/counttime)^1/2 

= (40 cpm/2 m)^1/2 

= +/- 4.47 cpm

The approximate exposure rate (R/hr) at a point one foot from a 

3.0 Ci source of Co-60 which emits two gamma photons, one with an 

energy of 1.17 MeV and the other with an energy of 1.33 MeV is: 

A) 28 R/hr 

B) 45 R/hr 

C) 21 R/hr 

D) 22.5 R/hr 

E) 24 R/hr 


D = 6CEN 

= 6{(3.0)[(1.17 x 1.00) + (1.33 x 1.00)]} R/hr 

= 45 R/hr

Which of the following is a disadvantage of a TLD versus a film 

badge for external radiation dosimetry? 

A) TLDs are not weather resistant 

B) TLDs cannot be reused 

C) TLDs leave no permanent record 

D) TLDs are less durable 

E) TLDs are more awkward for personnel 


Once the TLD is annealed, the actual response in the dosimeter 

has been removed. If for some reason the results are not 

recorded properly, the data is lost. Most TLD systems have 

backup TL chips for this reason.

What materials are most commonly used as filters in film badges? 

A) paraffin, plastic, teflon 

B) plastic, teflon, aluminium 

C) plastic, aluminium, lead 

D) cadmium, tin, paraffin 

E) paraffin, polyurethane, teflon 


Materials of varying density thicknesses are used as filters in 

film badges to correct for tissue equivalence, energy dependence, 

and to discriminate between types of radiation.

If two gamma photons of different energies interact with a 

detector in a gamma spectroscopy system at the same time, the 

resulting spectrum will show: 

A) a peak at the average energy of the photons 

B) a peak at the sum of the energies of the 

photons 

C) a peak at the higher photon energy only 

D) a peak at the difference of the two photon 

energies 

E) peaks at each discrete photon energy only 


The pulse height registered in the detector will be a sum of the 

pulse heights of each energy photon. The probability that both 

photons will interact simultaneously, however, is low. More 

counts will be registered in the assigned channels for each 

energy photon, rather than in the channel representing the sum 

value.

An individual breathes a concentration of 5.0 E-8 microcuries/ml 

of Cobalt-60 for one and one-half hours. If the DAC for 

Cobalt-60 is 9.0 E-9 microcurie/ml, his approximate whole body 

dose from this intake will be: 

A) 5.55 millirem 

B) 2.1 millirem 



E) 1.4 millirem 


Assuming the DAC is based upon the sALI, one DAC-hour is equal to 

a CEDE of 2.5 mrem. So: 

DAC-fraction x time(hrs) x 2.5 mrem/DAC-hr = CEDE 

(5.0 E-8/9.0 E-9) x 1.5 hrs x 2.5 = 20.83 mrem

The approximate exposure rate (R/hr) at a point 3 feet from a 2.5 

Ci source which emits a 0.501 MeV gamma photon is: 

A) 0.5 R/hr 

B) 0.8 R/hr 

C) 2.5 R/hr 

D) 7.5 R/hr 

E) 29.9 R/hr 


Using D = 6CEN, we must assume that N = 1 since it is not given. 

Then, using the inverse square law: 

D = [6(2.5)(0.501)(1.00)]/(3)^2 

= 0.835 R/hr

The MOST effective bioassay method to detect uptake of tritium 

is: 

A) nasal smears 

B) fecal analysis 

C) urinalysis 

D) liquid scintillation whole body counter 

E) solid crystal scintillation whole body 

counter 


Since tritium is an isotope of hydrogen, it is readily taken up 

in body water and excreted via the urine. Urine is especially 

adaptable to liquid scintillation counting, which is required for 

tritium detection.

A sample is measured using a proportional counter. 100 counts 

are observed in seven minutes. What is the counting rate and its 

associated standard deviation? 

A) 14.3 cpm +/- 1.4 cpm 

B) 14.3 cpm +/- 7.4 cpm 

C) 14.3 cpm +/- 3.9 cpm 

D) 100 cpm +/- 7 cpm 

E) 100 cpm +/- 10 cpm 


The counting rate and the standard deviation (1 sigma) are 

calculated as follows: 

countrate/counttime +/- (countrate/counttime)^1/2 

100 c/7 min +/- (100/7/7)^1/2 

14.28 +/- 1.43 cpm

According to 10 CFR Part 20, the quality factor for high energy 

protons is: 

A) 1 

B) 10 

C) 20 

D) 50 

E) 100 


Quality factors are defined in 10 CFR Part 20 (1991) in Table 

1000.4(b).1. for all ionizing radiations. These follow 1977 

recommendations of the ICRP.

Which of the following is not on a preoperational instrument 

check list? 

A) the battery voltage 

B) the old readings from the previous surveys 

C) the next calibration date on the calibration 

level 

D) the response of the instrument to a known 

source 

E) the physical damage check 


Five items to be checked on a portable radiation detection 

instrument prior to use: 

Calibration valid 

Battery good 

Physical damage check 

Zeroed (if applicable) 

Response check

When calibrating radiation detection instruments, all of the 

following must be considered EXCEPT: 

A) scattering 

B) prevailing wind direction 

C) barometric pressure 

D) ALARA 

E) temperature 


Wind direction has no bearing on the response of these 

instruments. It is, however, a great consideration when 

calculating atmospheric dispersion of radioactive materials. The 

other distractors are valid calibration considerations.

The dose in rads due to energy desposition from P0-210 alpha 

particles which would cause the same dose equivalent as 10 rem of 

fast neutrons is: 

A) 0.5 

B) 1 

C) 5 

D) 10 

E) 20 


We know that 

rads x QF = rems 

so 

rads x 20 = 10 rems 

rads = 0.5

Which of the following is the best choice for measuring the dose 

from Kr-85? 

A) criticality dosimeter 

B) cutie pie 

C) TLD 

D) GM survey meter 

E) vibrating reed electrometer 


Since Kr-85 is a beta-gamma emitting external hazard, and dose is 

the quantity to be measured, the TLD is the best choice.

A worker spends 10 minutes in a radation field of 250 mR/hr 

gamma, 100 mrad/hr thermal neutrons, and 40 mrad/hr fast 

neutrons. The total dose equivalent to the worker for this 

period is about: 

A) 880 mrem 

B) 160 mrem 

C) 125 mrem 

D) 88 mrem 

E) 65 mrem 


The appropriate quality factors (QFs) are as follows: 

Gamma 1 



then 

Dose equivalent(rems) = dose(rads) x QF 

and 

dose rate x time = dose 

so 

(250 x 1)+(100 x 3)+(40 x 10)mrem/hr x (10m x 1hr/60m) 

= 158.33 mrem

The DAC for inert gases is based on: 

A) internal exposure 

B) external exposure 

C) both internal and external exposure 

D) the DACs of their radioactive daughters 

E) the "4 Pi Factor" 


Since inert (or noble) gases do not remain inside the body, they 

pose a greater external than internal hazard. The DACs for 

radioactive inert gases are typically based upon a 2000 hour 

"submersion dose" of 5 rem CEDE, or a 2000 hour shallow dose 

equivalent of 50 rem (ICRP 1977,10 CFR 20 1991).

A researcher is working with a 0.5 millicurie Cs-137 source for 

7 hours at a distance from his hand of 7 cm. The specific gamma 

constant is 3.33 R cm^2 mCi^-1 hr^-1. What is his extremity 

dose? 

A) 0.23 rem 

B) 0.476 rem 

C) 3.33 rem 

D) 11.65 rem 

E) 23.32 rem 


D = GA/r^2 

where 

D = absorbed dose rate (rad/hr) 

G = specific gamma constant 

A = activity (mCi) 

r = distance 

So 

D = (3.33 R cm^2 mCi^-1 hr^-1)(0.5 mCi)/(7cm)^2 

= .034 rad/hr 

and 

.034 rad/hr x 7 hrs = 0.238 rad 

and, for gamma, = 0.238 rem

The absorbed dose from the alpha particles emitted from Po-210 is 

100 ergs in a gram of tissue. The dose equivalent in this tissue 

mass is: 

A) 1 rem 

B) 10 rem 

C) 10.43 rem 

D) 20 rem 

E) 50 rem 


rem = rad x QF 

and 

100 ergs/gm = 1 rad 

and 

QF for alpha = 20 

So 

(100 ergs/gm x 1 rad/100 ergs/gm) x 20 = 20 rem

The use of albedo dosimeters for fast neutron dose assessment 

relies on what major principle to produce a response in the 

dosimeter? 

A) fast neutrons release photons from the 

hydrogenous material in the badges and these 

photons deposit energy in the dosimeter 

B) fast neutrons are thermalized in the body, 

and the thermalized neutrons are scattered 

partially into the dosimeter 

C) fast neutrons are moderated in the 

hydrogenous material of the badge and produce 

a response in the dosimeter 

D) radiative capture interactions in the body 

ionize the TLD material 

E) (n,a) interactions in the body ionize the TLD 

material 


The term "albedo" means "reflecting". Scattering interactions 

with hydrogen in the body reflects thermal neutrons into the 

dosimeter.

An Airborne Radioactivity Area must be posted at one DAC or 

_________ DAC-hour(s) to an individual in one week. 

A) 0.25 

B) 1 

C) 6 

D) 12 

E) 25 


This definition of Airborne Radioactivity Area comes from 10 CFR 

Part 20 (1991). 12 DAC-hours in a 40-hour week can be used to 

establish a posting threshold of .3 DAC.

The minimum detectable activity for a counting system is: 

A) a measure of the efficiency of the detector 

B) an indication of the range of energy response 

C) a measure of the counting efficiency 

D) an estimate of the lowest sample activity for 

which activity should be considered present 

E) a time weighted average of the count rate for 

all samples of a specific condition at the 

time of counting 


Calculation of the MDA is dependent upon background count rate 

and count time, as well as sample count time. Increasing 

background and sample counting times will decrease MDA. An 

increase in background count rate will increase MDA.

Albedo dosimetry will function properly if: 

A) the individual's body water is evaluated and 

fast neutrons are reflected from the body 

into the dosimeter 

B) a cadmium filter is used between the 

dosimeter and the external neutron field, and 

neutrons are reflected from the body into the 

dosimeter 

C) the neutron spectrum is evaluated and fast 

neutrons are reflected into the dosimeter 

D) the individual's body water is evaluated and 

the neutron spectrum is evaluated 

E) the individual's body water is evaluated and 

a cadmium filter is used between the 

dosimeter and the external neutron field 


The cadmium filter, which has a high capture cross section for 

neutrons over a fairly broad energy range, is used to shield 

against ambient thermal neutrons. The term "albedo" means 

"reflecting".

Which of the following detectors operates in a voltage region 

where gas mulitplication effects are observed? 

A) TLD 

B) proportional counter 

C) CsI scintillator 

D) zinc-sulfide detector 

E) air ionization chamber 


The only two gas-filled detectors shown are the proportional 

counter and the ionization chamber. The ionization chamber 

operates in the "current" rather than the "pulse" mode, where no 

amplification of initial ions occurs.

What is the ionization region? 

A) the region of current over which the 

saturation current is produced 

B) the region of voltage over which the 

saturation current is produced 

C) the region of voltage over which ionization 

is taking place 

D) the region of current over which ionization 

is taking place 

E) the region of current over which the 

saturation voltage is produced 


The operation of a gas-filled detector in the "current" mode, as 

opposed to the "pulse" mode, places it in the ionization region 

of voltage in the six-region curve for gas-filled detectors. In 

the ionization region of voltage, one electron reaches the 

detector electrode (anode) for each electron released by 

ionization in the detector. This is called the "saturation 

current".

The value used to relate the linear energy transfer of a 

particular type of radiation to its relative biological 

effectiveness is: 

A) collision stopping power 

B) attenuation coefficient 

C) absorption factor 

D) quality factor 

E) tissue weighting factor 


Quality factor is defined in ICRP Publication 26 (1977) as a 

function of the collision stopping power of a radiation in water. 

It has been replaced in ICRP Publication 60 (1990) with 

"radiation weighting factor". Quality factor and radiation 

weighting factor are most dependent upon the LET of the 

radiation.

The difference between x-ray and neutron responsive films is: 

A) the grains are the same size and the emulsion 

is thicker and may be in several layers in 

neutron film 

B) the grains are larger and the emulsion is in 

several layers in x-ray film 

C) the grains are the same size and the emulsion 

is thicker and may be in several layers in 

x-ray film 

D) the grains are smaller and the emulsion is 

thicker in neutron film 

E) the grains are smaller and the emulsion is 

the same thickness in neutron film 


In neutron track film, the emulsion is about three times thicker 

than x-ray film and the grain size is reduced from between 1 and 

2 to about 0.3 micron. These conditions enhance the production 

of the proton recoil tracks in the film.

THe ICRP lung model has divided the respiratory tract into three 

compartments. They are: 

A) upper respiratory tract, lower respiratory 

tract, and alveoli 

B) upper respiratory tract, tracheal/bronchial 

tree, and pulmonary 

C) nasopharynx, pulmonary, and lymph 

D) nasopharynx, tracheal/bronchial tree, and 

pulmonary 

E) naspharynx, tracheal/bronchial tree, and 

alveoli 


There are four internal models presented in the 1977 

recommendations of the ICRP in Publication 30. They are the 

lung, gastrointestinal tract, bone, and submersion models. 

Typically, each relies on first order kinetics and consists of 

sequential compartments. The compartments for the lung model are 

addressed in this question.

Three different labs measure the same NIST-traceable source and 

determine count rates to the 68.3% confidence level of 3000 +/- 

30, 2900 +/- 35, and 3100 +/- 25. How should the results be 

expressed? 

A) 3000 +/- 9 

B) 3000 +/- 25 

C) 3000 +/- 30 

D) 3000 +/- 35 

E) 3022 +/- 9 


In this situation, the mean of the sample value and the largest 

margin of error should be used to express the composite result.

Which of the following five detectors would provide the most 

accurate measurement of exposure rate in a mixed energy gamma 

field? 

A) Geiger-Mueller detector 

B) Zn S scintillation detector 

C) Na I scintillation detector 

D) Air ionization chamber 

E) BF3 detector 


Since exposure rate is a measurement of ionization of air, the 

most direct and accurate instrument would be the air ionization 

chamber. GM detectors do not provide a direct measurement of 

exposure and may overrespond at lower energies.

An ionization chamber which as a diameter greater than the 

diameter of a monoenergetic gamma beam will: 

A) overrespond to the beam 

B) underrespond to the beam 

C) respond correctly to the beam 

D) alternately respond correctly and overrespond to the beam, 

depending upon the fill gas pressure 

E) alternately underrespond and overrespond to the beam, 

depending upon the fill gas pressure 


Since the instrument is calibrated under a uniform field, the 

entire detector wall is subject to ionization. When only part of 

the wall is subjected to ionization, such as in this narrow beam 

scenario, not as much current is produced, and so, a lower 

response.

The major routes of entry of radionuclides into the body are: 

A) absorption through the skin and inhalation 

B) inhalation and ingestion 

C) absorption through the skin and ingestion 

D) through wounds and ingestion 

E) through wounds and inhalation 


Inhalation and ingestion are the two most common routes of 

radionuclide intake, occupationally or otherwise. Inhalation is 

generally more predominant than ingestion.

A NaI counting system would be appropriate for measurement of the 

radioactivity concentration in water of all of the radionuclides 

listed EXCEPT: 

A) Sr-90 

B) Cs-137 

C) Co-60 

D) I-131 

E) Cs-134 


Sr-90 is the only "pure beta-emitter" listed. All other nuclides 

listed include significant gamma emissions in their beta-minus 

decays.

Bonner spheres are used to characterize neutron spectrums. This 

is accomplished by: 

A) the use of cadmium filters 

B) selectively thermalizing neutrons of varying 

energies 

C) the use of alpha spectroscopy on the B-10 

(n,a) Li-7 reaction 

D) comparison to Long counter results 

E) the use of boronated plastic scintillators 


Using different diameter polyethylene spheres with a central BF3 

detector enables the researcher to plot the contribution of 

varying energy neutrons to the total spectrum. This works 

because it takes different thicknesses of a material to 

thermalize neutrons of different energies. The BF3 detector 

responds only to the thermalized neutrons.

A person is standing in a semi-infinite cloud of Krypton-88 (2.39 

MeV gamma, 0.196 MeV gamma) with a concentration of 2.0 E-2 

microcuries per milliliter. If the person remains there for 

fifteen minutes, his whole body gamma radiation dose will be: 

A) 2.1 rem 

B) 7.7 rem 

C) 11.6 rem 

D) 19.6 rem 

E) 21.1 rem 


The absorbed deep dose from submersion in a cloud of 

gamma-emitting noble gas can be estimated as 

D = .25 EX 

where 

D = rad/sec 

E = gamma energy (MeV) x yield 

X = concentration (uCi/cc) 

and 

Dose rate x time = dose 

and 

yield is not given, so 1 must be assumed 

So 

{.25[(2.39x1.00)+(0.196x1.00)](2.0 E-2)}x(15m x 60s/m) 

= 11.64 rad 

and, for gamma(QF = 1) 

= 11.64 rem

A chemical which has shown some success as an internal chelating 

agent for plutonium is: 

A) diethylenetriaminepentaacetic acid (DTPA) 

B) thenolytrifluoracetone (TTA) 

C) versene 

D) potassium permanganate (KMnO4) 

E) nitrile triacetic acid (NTA) 


DTPA is typically used as a chelating agent for Pu and Am. For 

Cs-137, Prussian blue is somewhat effective. KMnO4 is used as a 

topical decontamination agent when soap and lukewarm water are 

ineffective.

The net counts observed from successively counting a sample are 

plotted on semilog paper, and the plot forms a curved line. It 

is probable that: 

A) the counting system was not working properly 

B) the sample contained more than one 

radionuclide 

C) the effective half-life obtained from the 

initial counts is the correct half-life 

D) the half-life obtained is the correct 

half-life of the longest lived radionuclide 

in the sample 

E) the half-life cannot be determined by 

repetitive counts of the sample 


Since radioactive decay of a single radionuclide is a lognormal 

function, it appears as a straight line on a semilog graph. If 

two nuclides with different half-lives are present, the resulting 

curve is a sum of two straight lines with different slopes.

The most appropriate survey instrument for the detection of 

Pu-239 surface contamination is one which utilizes a(n): 

A) GM detector 

B) NaI(Tl) detector 

C) zinc sulfide detector 

D) ionization chamber 

E) boron trifluoride counter 


Since Pu-239 decays by alpha, with only a weak gamma emitted, the 

detector which is most efficient for alpha is chosen.

For NaI and GeLi detectors, as gamma energies increase above 200 

keV, the efficiency of the detector is: 

A) linear 

B) decreased 

C) increased exponentially 

D) increased proportionally 

E) supralinear 


Above 200 keV, Compton effect begins to predominate for gamma 

interactions in a material. For a given incident photon energy 

whose accurate measurement is dependent on photoelectric effect, 

efficiency is reduced. Higher energy photons are also less 

likely to interact with the detector material at all, further 

decreasing the efficiency as photon energy increases.

The exposure rate at three feet from a five curie Cesium-137 

point source is approximately: 

A) 1 R/hr 

B) 2 R/hr 

C) 3 R/hr 

D) 4 R/hr 

E) 5 R/hr 


Using D = 6CEN and the inverse square law: 

D = [6(5)(.662)(.85)]/(3)^2 

= 1.875 R/hr

Ar-41 is a noble gas which decays by a 1.2 Emax beta and a 1.29 

MeV gamma photon. Which of the following statements regarding 

exposure in a cloud of Ar-41 is INCORRECT? 

A) If the Ar-41 concentration is equal to the 

occupational DAC the external radiation dose 

rate to an individual standing on the ground 

would be 2.5 mrem/hr 

B) Since the cloud is very large, it is 

realistic to neglect the beta contribution to 

the body surface dose 

C) The lung dose resulting from inhalation is 

small compared to the external dose received 

from the direct radiation from the cloud 

D) The surface dose rate to the body will exceed 

the dose rate at any depth in the body 

E) A person standing on the ground is immersed 

in a "semi-infinite" cloud of Ar-41 


Since only a 70 keV beta particle is required to penetrate to the 

basal layer of the skin, a 1.2 MeV Emax beta-emitter will be 

contributing significantly to the "body surface" dose. All other 

presented data are valid.

An instrument that gives a direct exposure rate reading from 

ionizing photon radiation is: 

A) a quartz fiber self-reading dosimeter 

B) a liquid scintillation counter 

C) an air ionization chamber survey meter 

D) a silver halide film badge 

E) a boron trifluoride counter 


Exposure is ionization of air by photons. The only two insruments 

shown which give a direct response to exposure are A and C. A 

quartz fiber self-reading dosimeter, however, gives an integrated 

reading, not a rate.

The exposure rate at two feet from a point source is 20 R/hr. 

What is the expected exposure rate at four feet from the source? 

A) 5 R/hr 

B) 10 R/hr 

C) 1.25 R/hr 

D) 0.1 R/hr 

E) 0.5 R/hr 


Use the inverse square law: 

R1 (D1)^2 = R2 (D2)^2 

20 R/hr (2)^2 = R2 (4)^2 

R2 = 5 R/hr

When using a TLD badge with TLD 600 and TLD 700 chips, the 

neutron contribution is determined by: 

A) subtracting the TLD 600 from the TLD 700 

reading 

B) subtracting the TLD 700 from the TLD 600 

reading 

C) averaging the response of both chips to 

thermal range neutrons 

D) adding the response of both chips to thermal 

range neutrons 

E) it is not possible to determine neutron dose 

equivalent with this configuration 


The TLD 700 chip contains natural lithium, which is mostly Li-7 

and is primarily gamma responsive. The TLD 600 is natural 

lithium enriched in Li-6, which is neutron responsive from the 

Li-6(n,alpha)H-3 reaction, but contains enough Li-7 to also be 

gamma responsive. So, to obtain the neutron contribution, the 

TLD 700 (gamma only) is subtracted from the TLD 600 (neutron and 

gamma) reading.

A worker spends 90 minutes in a field of 120 mR/hr gamma, 40 

mrad/hr thermal neutrons, and 80 mrad/hr fast neutrons. The 

total whole body dose equivalent to the worker for this period 

is: 

A) 240 mrem 

B) 360 mrem 

C) 1320 mrem 

D) 1560 mrem 

E) 1980 mrem 


The appropriate quality factors are as follows: 

Gamma 1 



and 

rad X QF = rems 

and 

dose rate x time = dose 

So 

[(120 x 1)+(40 x 3)+(80 x 10)] x (90 min/60 min/hr) 

= 1560 mrem

A sample counted for ten minutes yields 3000 counts. A 20 minute 

background count yields 2400 counts. The net counting rate at 

the 95% confidence level is: 

A) 240 +/- 15 c/m 

B) 180 +/- 4 c/m 

C) 180 +/- 6 c/m 

D) 180 +/- 12 c/m 

E) 180 +/- 18 c/m 


Net count rate = samplerate - bkgrate 

and 

2 sigma= 


so 

(3000/10)-(2400/20)+/- 

1.96[(2400/20/20)+(3000/10/10)]^1/2 

= 

180 +/- 11.76 cpm

Obtaining reproducible results during a check of a radiation 

detection instrument is a measurement of: 

A) accuracy 

B) precision 

C) validity 

D) conformity 

E) deviation 


Precise results are those that can be corrected consistently to 

an accurate value through the use of the detector efficiency, a 

correction factor, or a calibration graph. The ability to 

consistently correct to an accurate value is precision.

Nominal counting efficiencies of a 2 Pi proportional counter for 

alpha and beta sources, respectively, would be: 

A) 50% and 10% 

B) 50% and 40% 

C) 50% and 65% 

D) 75% and 50% 

E) 75% and 100% 


Nominal efficiency in this case takes into account only geometry 

effects. Since one half of the sample is exposed to the detector 

in 2 Pi geometry, the nominal efficiency for a high-LET radiation 

such as alpha would be 50%. Since beta particles will scatter 

into the detector from the sample holder, the nominal efficiency 

for beta particles will be greater than 50%. The answer which 

fits this decision logic is C.

A worker stands 12 feet from a gamma point source which reads 3 

R/hr at 3 feet. If the worker remains there for three hours and 

breathes 10 DAC air the entire time, what is his approximate 

total effective dose equivalent? 


B) 610 millirem 





TEDE = DDE + CEDE 

and,using the inverse square law 

DDE = [(3 R/hr)(3)^2]/(12)^2 x 3hrs 

= .1875 rem/hr x 3 hrs 

= .5625 rem 

= 562.5 mrem 

and 

CEDE= (10 DAC x 3 hrs) x 2.5 mrem/DAC-hr 

= 75 mrem 

So 

TEDE= 562.5 mrem + 75 mrem 

= 637.5 mrem

Glass is frequently selected as a material for liquid 

scintillation vials in the analysis of tritium, primarily to: 

A) prevent diffusion of the tritium from the 

sample 

B) enhance the light output from the sample 

C) minimize optical quenching in the system 

D) minimize chemical quenching in the system 

E) avoid undue natural background radiation from 

the components of plastic liquid 

scintillation vials 


Since plastic is a hydrogenous material, H-3 will readily diffuse 

from a sample into the plastic vial. Glass does have the 

disadvantages of natural radioactivity and optical quenching.

Determine the mean of the following set of sample results: 

233 cpm 

270 cpm 

249 cpm 

239 cpm 

250 cpm 

A) 250.2 cpm 

B) 251.5 cpm 

C) 247.8 cpm 

D) 248.2 cpm 

E) 1241 cpm 


To obtain the mean, simply take the sum of n results and divide 

by n. 

So 

(233+270+249+239+250)/5 = 248.2

When a radionuclide is taken into the body, the extent of damage 

is determined by: 

A) the type of radiation emitted and its 

half-life 

B) the rate at which the radionuclide is 

excreted from the body 

C) the place of deposition of the radionuclide 

in the body 

D) all of the above 

E) both A and B 


All of these factors must be taken into account to properly 

estimate the dose and resultant potential damage from a 

radionuclide intake.

The full width of a given photopeak at half the maximum peak 

height, identified with a photon energy of 1 MeV, is 1.8 keV. 

The percent resolution of the detector at 1 MeV is: 

A) 1.8% 

B) 0.0018% 

C) 0.18% 

D) 18% 

E) 0.018% 



= (1.8 keV/1000 keV) x 100% 

= 0.18%

In the ionization region of a gas-filled detector, the output 

current is approximately: 

A) proportional to the energy of the radiation 

entering the detector 

B) equal to the energy of the radiation entering 

the detector 

C) independent of the voltage over a fairly 

large voltage range 

D) the same size regardless of the type of 

energy of the radiation 

E) independent of the fill gas 


In the ionization region, there is a current of electrons 

produced which is equal to the number of initial ionizations 

produced in the detector. The current is independent of the 

voltage over a fairly broad range, the range being dependent on 

detector volume and fill gas characteristics.

In the G-M region of a gas filled type detector, the output: 

A) is approximately proportional to the energy 

of the radiation entering the detector 

B) decreases to zero in a high radiation field 

C) pulse height is independent of the type and 

energy of the radiation entering the detector 

D) pulse height is independent of the voltage on 

the chamber over a fairly large voltage range 

E) pulse is proportional to the amount of the 

primary ionization produced in the gas 


In the G-M region, the voltage is high enough such that one 

triggering event of any type of ionizing radiation will produce 

complete ionization of the detector fill gas, creating the same 

height pulse for any initiating event. Regarding choice B, 

modern G-M detectors are designed to fail high in high radiation 

fields.

Unless some type of quenching is used, a geiger-mueller detector 

will re-trigger because of: 

A) breakdown of the detector gas caused by 

severe ionization 

B) creation of satellite pulses 

C) reduction in ion density due to recombination 

D) release of electrons from the cathode during 

the collection of positive ions 

E) release of electrons from the anode during 

the collection of negative ions 


When the fill gas molecule in a G-M or proportional counter is 

ionized, the negative ion (electron) reaches the electrode 

(anode) much quicker than the positive ion would reach the wall 

(cathode). If the positive ion did reach the wall, additional 

electrons would be released, causing another pulse in the 

detector. For this reason, quenching molecules are added to the 

fill gas to combine with the positive ions before they reach the 

detector wall.

Which of the following materials is commonly found in 

photoneutron sources? 

A) tantalum 

B) carbon 

C) beryllium 

D) cobalt 

E) aluminum 


Since beryllium has a low nuclear binding energy, it is often 

combined with gamma or alpha emitting nuclides to produce a 

neutron source. A typical photoneutron source is SbBe, used as a 

"startup source" in nuclear reactors.

At medium gamma energies (100-300 keV), the BEST explanation for 

the decrease in Ge(Li) detector counting efficiency is: 

A) photoelectric absorption decreases linearly 

when graphed on a log-log scale 

B) Compton scattering decreases linearly when 

graphed on a log-log scale 

C) pair production does not become a significant 

interaction in Ge(Li) untiul gamma energies 

are above 5 MeV 

D) energy absorbed from Compton scattering 

decreases with increasing energy 

E) the K-edge for Ge(Li) occurs at 4 MeV 


Since the efficiency of a gamma spectroscopy is largely dependent 

on the full transfer of energy from the incident photon to 

electrons in the detector (photoelectric effect), higher energies 

where Compton interactions predominate result in a reduced 

efficiency. Compton interactions begin to predominate at 200 

keV.

The average number of ion pairs produced by a 100 keV beta 

particle that stops in air is approximately: 

A) 30 

B) 300 

C) 3,000 

D) 30,000 

E) 300,000 


The "W" value for air (dry air at STP) is 33.7 eV. So: 

(100 keV x 1 E3 eV/keV)/(33.7 eV/ion pair) 

= 3000 ion pairs

A simultaneous operating mode is used by proportional counting 

systems to: 

A) count more than one sample at a time 

B) count more than one sample type 

C) account for fluctuating background levels 

D) count alpha and beta particles at the same 

time 

E) count beta and gamma emitters at the same 

time 


The simultaneous mode uses pulse height discriminators to 

register alpha and beta-gamma pulses in different channels. The 

higher LET alpha radiation causes a higher pulse in the 

proportional region when counted simultaneously with beta 

particles.

An important advantage of using a halogen quenching gas rather 

than an organic quenching gas in a G-M detector is: 

A) halogen gases have a lower ionization 

potential so they also have an increases 

sensitivity 

B) organic gases corrode the detector 

C) organic gases can be depleted thus losing the 

quenching required for the detector while the 

halogen is self rejuvenating 

D) halogen gases are better conductors 

E) it makes the instrument lighter 


Organic quench gases such as methane have a distinct life, 

usually expressed in total counts detected. Inorganic quench 

gases such as bromine are self-rejuvenating and, thus, have an 

indefinite life. This may be an important quality in a fixed 

volume, sealed detector.

A worker has an inhalation intake of 1000 Bq of Class Y Co-60 and 

6000 Bq of Class D I-131. The ICRP 30 stochastic based annual 

intake limits are 1E+6 Bq and 6E+6 Bq respectively for Co-60 and 

I-131. Lacking any other specific information, the worker's 

committed effective dose equivalent is properly estimated as: 

A) 10 mrem 

B) 8 mrem 

C) 6 mrem 

D) 4 mrem 

E) 2 mrem 


CEDE = (intake/sALI) x 5 rem 

= [(1000/1 E6)+(6000/6 E6)] x 5 rem 

= 10 mrem

The target organ for most transportable long lived alpha emitters 

is: 

A) the gonads 

B) the lung 

C) the gastrointestinal tract 

D) the bone surfaces 

E) the breast 


The heavy metals, which tend to decay by alpha emission and have 

long half-lives, affix themselves to the bone surfaces when taken 

in to the body.

Silver zeolite is the medium of choice for iodine sampling 

primarily because of its: 

A) high collection efficiency for iodine 

B) long shelf life 

C) low cost 

D) low affinity for noble gas 

E) low natural radioactivity content of silver 

zeolite 


When sampling for radioiodines in the presence of noble gases, 

such as during fission accident scenarios, the ability of silver 

zeolite to collect iodine with little affinity for inert fission 

gases is desirable.

The short-lived Radon (Rn-222) decay products are: 

A) Po-226,Bi-214,Po-218,Bi-216 

B) Pb-214,Po-214,Bi-216,Po-218 

C) Bi-214,Pb-214,Po-218,Po-214 

D) Po-214,Ra-226,Rn-220,Pb-214 

E) Po-216,Pb-212,Bi-212,Po-212 


These are the nuclides that are included in the definition of 

"working level" and produce the majority of natural background 

radiation exposure by inhalation.

Carbon dating is possible because: 

A) the specific activity of Carbon-14 in living 

organisms has changed over time and one can 

identify the era of time the organism lived 

based on its current specific activity 

B) Carbon-14 is in secular equilibrium with its 

daughter 

C) the specific activity of Carbon-14 in living 

organisms is relatively constant through 

time, but decays after the death of the 

organism 

D) the specific activity of Carbon-14 in wood 

increases over time due to shrinkage of the 

wood 

E) the specific activity of Carbon-14 in wood 

decreases over time due to shrinkage in wood 


All organisms establish an equilibrium level of C-14 while alive. 

After death, the intake ceases and the equilibrium level 

decreases as a function of the decay constant. If the 

equilibrium level is known for certain living organisms, the time 

elapsed after death can be calculated.

Which material is most likely to ionically bind with Cs-137 

before it migrates to groundwater? 

A) topsoil 

B) clay 

C) gravel 

D) mud 

E) sandstone 


Illite clay, such as that found below pond and river beds, has a 

particular affinity for cesium. It is a useful environmental 

indicator for Cs-137 dispersion.

Which of the following instruments would have good sensitivity to 

neutrons while providing the best discrimination against gammas? 

A) BF-3 proportional counter in polyethylene 

moderator 

B) GM tube at greater than 2 atmospheres in 

polyethylene moderator 

C) silverwrapped GM tube inserted in 

polyethylene moderator 

D) LiI(Eu) scintillator inserted in polyethylene 

moderator 

E) cadmium wrapped LiI(Eu) scintillator 


Since the BF-3 detector operates in the proportional region, and 

is set at an alpha voltage to detect the B-10(n,alpha)Li-7 

reaction, discrimination against gammas is excellent.

In a field of mixed neutron and gamma radiation, the gamma dose 

measured on a phantom is: 

A) greater than the gamma dose measured in air 

due to the H (n,gamma) D reaction in the 

phantom 

B) less than the dose measured in air due to the 

moderation of neutrons in the phantom 

C) the same as the measured dose in air because 

phantoms do not influence gamma irradiation 

D) less than the dose measured in air because 

some incident gamma rays are absorbed in the 

phantom 

E) not a quantity of interest in a dosimetry 

program 


Since the H concentration in tissue (represented by a phantom in 

this case) is much higher than that in air, it could be expected 

that the (n,gamma) reaction would produce a greater gamma 

contribution in the phantom than in air.

Which one of the following statements is TRUE regarding neutron 

bubble detectors? 

A) They are insensitive to intermediate energy 

neutrons 

B) They are accurate within +/- 30% in neutron 

dose rates of over 1000 rads/hr 

C) They are affected by temperature 

D) They cannot measure the total integrated dose 

E) They are not yet commercially available 


Neutron bubble detectors rely on superheated gas molecules in a 

polymer matrix to expand and "pop" when exposed to the heat of 

the H-1(n,gamma)H-2 reaction in the detector. The events are 

either recorded as number of bubbles created or number of "pops" 

registered by transducer. Since they rely on the heat of the 

reaction, they are temperature sensitive.

Tissue dose from thermal neutrons principally as a result of: 

A) (n,gamma) reactions with hydrogen 

B) (n,gamma) reactions with hydrogen and (n,p) 

reactions with nitrogen 

C) (n,p) reactions with carbon 

D) (n,alpha) reactions with carbon 

E) (n,alpha) reactions with carbon and (n,gamma) 

reactions with hydrogen 


Thermal neutrons interact by absorption (capture). These are the 

two significant thermal neutron interactions with tissue. Fast 

neutrons produce dose in tissue primarily through elastic 

scattering interactions with hydrogen, producing recoil protons.

Tissue dose from fast neutrons (0.1 to 14 MeV) is due primarily 

to: 

A) elastic scattering 

B) resonance scattering with nuclei 

C) inelastic scattering with nuclei 

D) Coulomb scattering with nuclei 

E) nuclear capture and spallation 


Elastic scattering with hydrogen produces high LET recoil 

protons, significant in fast neutron dose production in tissue.

The provisions of ANSI N13.11-1983 "American Dosimetry 

Performance Criteria for Testing" apply: 

A) to neither pocket dosimeters nor extremity 

dosimeters 

B) to pocket dosimeters but not to extremity 

dosimeters 

C) only to beta and gamma radiation 

D) to extremity dosimeters but not to pocket 

dosimeters 

E) to film badges but not to TLDs 


ANSI N13.11 represents NVLAP requirements for external dosimetry 

programs, which neither apply to pocket or extremity dosimeters.

ANSI N13.11-1983, "American National Standard for Dosimetry: 

Personnel Dosimetry Performance Criteria for Testing": 

A) forms the basis for the NVLAP for dosimetry 

processors 

B) provides guidance for individual variability 

from reference man 

C) provides guidance for summing the external 

and internal dose 

D) is applicable to the entire range of gamma 

energies 

E) is not required to be implemented by 10 CFR 

Part 20 


NVLAP represents the National Voluntary Laboratory Accreditation 

Program, which is not voluntary at all for "dosimetry processors" 

under 10 CFR Part 20.

If the skin were contaminated by an isotope with a half-life of 8 

days and assuming an exponential turnover time of the skin of 50% 

in 5 days, calculate the time to reduce the contaminant to 10% of 

the initial level. Assume decontamination has been ineffective. 

A) 1.1 d 

B) 3.1 d 

C) 7.1 d 

D) 10.2 d 

E) 43 d 


Use the effective half-life and decay formulas to solve. 

Teff = (Tb x Tr)/(Tb + Tr) 

= (5 x 8)/(5 + 8) 

= 3.077 days 

and 

lambda eff = .693/3.077 days 

= 0.225/day 

and 

A = Ao e^-(lambda x t) 

So let Ao = 1 

Then 

0.1 = 1 e^-(0.225 x t) 

ln(0.1) = -(0.225 x t) 

-2.3 = -0.225 t 

10.23 d = t

The PRINCIPAL detriment of long bioassay sampling periods for 

tritium is: 

A) the reduced ability to estimate actual doses 

received by workers 

B) the potential for an intake to escape 

detection 

C) the increased cost of the detriment 

D) the loss of prompt detection of tritium 

contamination in the work areas 

E) the reduced cost of the required bioassays 


Since H-3 has a short effective half-life, the frequency of 

bioassay periods for occupational exposures is generally about 2 

weeks.

Which statement is most accurate? 

A) it is hard to identify K-40 in the presence 

of 10 nCi of 60-Co 

B) the quantity of K-40 dose not vary by more 

than plus or minus 5% from individual to 

individual 

C) K-40 has no regulatory significance in a 

whole body counting program but serves as an 

important qualitative system check 

D) K-40 should be omitted from the radionuclide 

library for whole body counting since it is 

of no regulatory interest 

E) a multi-detector counter will typically not 

identify K-40 


Since K-40 is a significant naturally occurring radionuclide, 

ther is some level of K-40 in every individual's body. An 

in-vivo gamma spectroscopy result which does not show K-40 is 

suspect of counting error. ICRP 23 gives a value of 100 nCi of 

K-40 in reference man.

The major pathway by which soluble radioactive material is 

removed from the body is: 

A) perspiration 

B) feces 

C) urine 

D) respiration 

E) exhalation 


Urine represents the largest volume of liquid excretion from the 

body, and therefore is responsible for the greatest removal of 

soluble compounds and elements. This characteristic makes urine 

well-suited for in-vitro bioassay sampling.

Measurement uncertainty in a radiation measuring device is a 

function of: 

A) the method of detector operation 

B) the type of radiation measured 

C) both precision and accuracy in the 

measurement 

D) the magnitude of the quantity measured 

E) the significance of the hazard monitored 


Althogh A and B are correct responses, they are contributing 

factors to selection C, making it the best answer.

A sample counted for 10 minutes resulted in 1,000 counts. The 

background count was 250 counts in 10 minutes. Assuming 

negligible radioactive decay of the sample during counting, the 

net counting rate in counts per minute should be reported at the 

95% confidence level as: 

A) 750 +/- 35 

B) 75 +/- 7 

C) 75 +/- 10 

D) 75 +/- 3.5 

E) 75 +/- 14 



and 

2 sigma = 


So 

1000/10-250/10 +/-1.96[(1000/10/10)+(250/10/10)]^1/2 

= 

75 +/- 6.93 cpm

What is the most efficient ratio of sample counting time to 

background counting time given that the background counting rate 

is 10 counts per minute and the total counting rate with a sample 

is 1,000 counts per minute? 

A) 0.01 to 1 

B) 1.0 to 1 

C) 10 to 1 

D) 100 to 1 

E) 1,000 to 1 


The statistically optimum ratio of sample count time to 

background count time is calculated as: 

sampletime/bkgtime = (samplerate/bkgrate)^1/2 

= (1000/10)^1/2 

= 10

Which of the following is assumed to be a model of the human body 

for dosimetry calculations when made of unit density materials? 

A) a 15 cm by 30 cm rectangular block 

B) a 30 cm diameter sphere 

C) an ellipse with a 30 cm major diameter and a 

20 cm minor diameter 

D) a right circular cylinder of 30 cm height and 

15 cm diameter 

E) a right circular cylinder of 15 cm height and 

30 cm diameter 


The ICRU uses a 30cm diameter sphere of unit density in its 

recommendations on dose equivalent calculation.

When performing in-vivo measurements of personnel after a 

criticality accident to assess neutron dose, what is the nuclide 

of concern? 

A) I-131 

B) Cs-137 

C) Na-24 

D) N-16 

E) P-32 


For in-vivo measurements of criticality accident proportions, the 

Na-23(n,gamma)Na-24 reaction from large blood pools in the body 

(armpit, abdomen) is most useful.

9.25 E 11 Bq (25Ci) of a gas, with a half-life of 2.3 h, is 

uniformily distributed in the air in a 2.5m X 10m X 15m room. The 

effective room ventilation rate is 150 cubic meters/hour. After 

one hour, the activity concentration in the room is: 

A) 7.32 E8 Bq/cubic meter 

B) 1.10 E9 Bq/cubic meter 

C) 1.22 E9 Bq/cubic meter 

D) 1.73 E9 Bq/cubic meter 

E) 2.47 E9 Bq/cubic meter 


The removal mechanisms from the room are by decay and 

ventilation. Take both of these into account when calculating 

the effective removal constant. 

In the equation A = Ao e ^-(lambda x t) 

let A and Ao equal concentrations and let lambda equal the sum of 

the removal constants. 

So 

Ao = 9.25 E11 Bq/(2.5 x 10 x 15) m^3 

= 2.47 E9 Bq/m^3 

and 

lambda = (.693/2.3 hr)+[(150 m^3/hr)/375 m^3] 

= 0.7013/hr 

So 

A = 2.47 E9 Bq/m^3 {e^-[(0.7013/hr) x (1 hr)]} 

= 1.22 E9 Bq/m^3

Gas and aerosol detectors (smoke detectors) use radiation to 

cause ionization in the air between two electrodes, allowing an 

electric current to flow across the gap. The source most 

manufactors use is: 

A) Cs-137 

B) Am-241 

C) Ra-226 

D) Pu-239 

E) H-3 


Am-241 half-life = 433 yrs. Alpha emitters are used in smoke 

detectors, Ra-226 is another source used. NCRP 56

Using a dual energy subtraction x ray unit, the high contrast 

image of bone can be removed from the image by using the 

differences in: 

A) compton scattering angle of the two x rays 

B) x ray attenuation coefficients of the two x 

rays 

C) quality factors between the two x rays 

D)linear stopping power of the x rays 

E) x ray absorption coefficients of the two x 

rays 


In chest radiography, low energy x ray photons, such as are 

generated at 70 kVp, will produce images of both soft tissues and 

bone. Because of its relatively high absorption coefficient for 

low energy x rays, the bone image will present a high contrast 

relative to the surrounding tissue. A second image obtained with 

high energy x ray photons (130 kVp) will show much less bone 

contrast because of the reduction in photo-electric absorption. 

By computer subraction the bone images can be suppressed, leaving 

only a soft tissue image or the reverse, a bone image. 

Health Physics Journal Vol 69 No 5 (Webster 1995)

To obtain count rates that will fall in the mid-range of the 

mid-high range Noble gas effluent detectors when subjected to 

high gas concnetrations the detectors are designed with a: 

A) lower sensitivity and smaller viewing volume 

of gas 

B) higher sensitivity and smaller viewing volume 

of gas 

C) higher sensitivity and larger viewing volume 

of gas 

D) lower sensitivity and larger viewing volume 

of gas 

E) extreme sensitivity and smaller viewing 

volume of gas 


These detectors must have low sensitivity so that high gas 

concentrations will produce moderate count rates (

Laboratories designed to evaluate environmental samples taken 

from sited surrounding operating nuclear power plants must be 

designed to measure extremely low concentrations of 

radioactivity. Typical MDAs required for plant effluent releases 

are on the order of _____ to meet regulatory license requirments. 

A) 3.7 E-10 Bq/cm3 

B) 2.2 E-5 Bq/cm3 

C) 3.7 E-4 Bq/cm3 

D) 2.2 E-3 Bq/cm3 

E) 1.7 E-6 Bq/cm3 


10 CFR 20

Germanium-Lithium semiconductor detectors are limited by count 

rate due to: 

A) recommenatioon of ion pairs before electrons 

reach detector 

B) the cold temperatures maintained in the 

detector area 

C) the amount of lithium impurities 'drifted' 

into the Germanium crystal 

D) coincident circuitry limitations 

E) the width of the electrical pulses produced 


Pulse widths of ~100 micro seconds are common for GeLi detectors. 

Introduction to Radiochemistry, David Malcome-Lawes

Coincident circuitry is used in liquid scintillation detectors to 

eliminate the effects of: 

A) background radiation 

B) light current 

C) background noise 

D) thermionic noise 

E) tube temperature 


Circuit includes two PMTs which are used to discriminate against 

random noise pulses from the tubes by thermionic emission from 

the photocathodes of a PMT. 

Introduction to Radiochemistry, David Malcolme-Lawes

One of the components of the liquid scintillation cocktail is the 

solvent. Its purpose is to: 

A) keep the scintillator in solution and absorb 

the decay energy of the radioisotope 

B) keep the scintillator in the center of the 

cocktail and adsorb the light generated 

during decay of the radionuclide 

C) convert radionuclide excitation energy to 

light photons 

D) keep the scintillator in solution and shift 

the wave length of light emitted from the 

blue to red spectrum. 

E) keep the scintillator in solution and at the 

correct temperature for light production 


Introduction to radiochemistry, David Malcolme-Lawes

The function of the primary solute in a liquid scintillation 

cocktail is: 

A) remove the effects of ambient light on the 

scintillation process in the sample 

B) suspend the scintillator in solution and 

absorb the energy of decay from a 

radioisotope 

C) shift the emitted light photon wavelength so 

that the PMT can detect the photon 

D) convert the excitation energy of the solvent 

molecules into a light photon 

E) reduce the absorption of the light photons 

emitted by the scintillator 



A sample containing tritium, Carbon-14, and Phosphorus-32 is 

counted using a liquid scintillation counter. The sample 

generates three peaks. The radionuclides peaks from highest to 

lowest were: 

A) P-32, H-3, C-14 

B) H-3, P-32, C-14 

C) C-14, H-3, P-32 

D) C-14, P-32, H-3 

E) H-3, C-14, P-32 


Average beta energies emitted by H-3, C-14 and P-32 are 5.7 keV, 

49 keV, and 694 keV. 


The reduction of counting efficiency in liquid scintillation 

counters because of impurities, sample solvents and other 

materials of poor solvent category is called: 

A) wavelength shift 

B) photo reduction 

C) quenching 

D) adsorption 

E) dark current 



Quenching effects in a liquid scintillation counter are the 

result of two processes: 

A) chemical and color quenching 

B) color and temperature quenching 

C) percipitation and chemical quenching 

D) stratification and color quenching 

E) electrical and chemical quenching 


Chemical quenching is caused by de-excitation of electronically 

excited molecules which would otherwise emit photons. Color 

quenching is caused by adsorption of emitted photons by materials 

in a sample. 


A gamma spectrometer spectrum of a quantity of Cs-137 reveals two 

peaks one at 0.662 Mev and one at 32 keV. The 32 keV peak is due 

to: 

A) electron interactions with lead shielding 

B) internal conversion x-rays 

C) compton edge 

D) annilation xrays 

E) backscatter 


A radionuclide undergos decay emitting a gamma photon which 

interacts with an internal orbital electron. The electron absorbs 

the photon and is ejected from the atom. Another electron moves 

from a higher orbital shell to the vacated spot in the lower 

orbital. An x ray is emitted in the process. 

Introduction to Radiochemistry, David Malcomle-Lawes

A gamma spectrometer spectrum of a quantity of Co-60 reveals 

three peask. The smallest of the three peaks is at 2.5 MeV. This 

peak is the result of: 

A) interaction of Co-60 gammas with the lead 

shield 

B) backscatter 

C) decay of Co-60 

D) sumation of Co-60 gammas 

E) simultaneous production of Co-60 gammas 


Summing occurs when gammas are emitted in a very rapid succesion, 

cascade, during a decay. In this problem, Co60 decys by beta- to 

an excited state on Ni-60. Ni-60 goes to the ground state, 1.17 

and 1.33 MeV gammas are emitted ina very rapid succession. 


Summing of gamma photons on a gamma spectrometer spectrum can 

also occur between: 

A) gamma photons and annilation gammas 

B) gamma photons and Pb x rays 

C) gamma photons and internal conversion x rays 

D) Pb x rays and internal conversion x rayss 

E) annilation gammas and Pb x rays 


This compilation most commonly occurs with low energy gamma 

processes. 

Introduction to Radiochemistry, David Malcomle-Lawes

You are analyzing a sample containing Na-24 which emits two gamma 

photons at 2.76 MeV and 1.37 MeV with 100% abundance. On the 

gamma spectrometer spectrum two additional peaks are seen at 2.25 

MeV and 1.74 Mev. These two additional peaks are due to: 

A) escape of one or more pair production gammas 

from the detector 

B) another radionuclide contaminant in the 

sample 

C) backscatter from interaction with lead 

shielding 

D) activation gammas from detector walls 

E) relaxation gammas from sample 


pair production occurs to photons with energy in excess of 1.022 

MeV. The e+ e- pair created in the detector cause the production 

of the two peaks. In this case either all the original photon 

energy will be detected as charge particles loose their kinetic 

energy and annilate with both photons being detected OR one or 

both of the two 0.511 MeV photons will escape from the crystal 

without being detected. 

2.76 - 0.511 = 2.25 2.76 - 0.511 = 1.74 


With large gamma energies, the compton edge will occur at ____ of 

the photopeak energy. 

A) 75% 

B) 95% 

C) photopeak energy + 150 keV 

D) photopeak energy - 250 keV 

E) 65% 


Introduction to radiochemistry, David Malcolme-Lawes

To improve the efficiency of an instrument, you must create a 

situation where more of the source disintegrations are recorded. 

All of the methods below improve efficiency EXCEPT: 

A) minimize self adsorption in the sample 

B) change the detector type 

C) increase detector size 

D) change detector shape 

E) move the detector farther from the source 


Need to move the sample closer to the detector 

Introduction to Radiochemistry, David Malcolmne-Lawes

To avoid excessive dead time on multi-channel gamma analyzers you 

should keep samples below: 

A) 100 mr/hr at 30 cm 

B) 100 mr/hr at 2 inches 

C) 10 mr/hr at 2 inches 

D) 1 mr/hr at 30 centimeters 

E) 5 mr/hr at 1 meter 


EPRI Rad Waste Reference Question 1621

You are assigned to count a number of environmental samples. To 

meet the required LLDs you need to adjust a number of the 

counting parameters. To increase the LLD value what must you do 

to: sample size, count time and detector background? 

A) increase sample size, decrease count time, 

increase detector background 

B) decrease sample size, decrease count time, 

reduce detector background 

C) increase sample size, decrease count time, 

reduce detector background 

D) increase sample size, increase count time, 

reduce background 

E) decrease sample size, increase count time, 

increase detector background 


EPRI Rad Waste Desk Reference Question 1623

You have received a hot particle recovered from an individual. 

To determine the type of particle, fuel or crud, the best method 

to use is: 

A) allow the particle to decay for half-hour and 

recount 

B) use a 90 mg/cm2 shield and observe the change 

in count rate 

C) cover particle with plastic and recount 

D) survey the particle with an alpha meter 

E) use a magnet and observe particle response 


NRC Information Notice IN 90-48: crud particle betas are of a 

lower energy than fuel hot particles. The plastic shield will 

significantly reduce the crud betas while most of the fuel betas 

will pass through.

The method used to determine the amount of uptake of C-14 is: 

A) whole body count 

B) urinalysis 

C) blood analysis 

D) breath analysis 

E) fecel analysis 


Capture an individual's breath with a ballon or bag abd count for 

C-14. Looking for CO2 on exhalation from exposed individual. 

Moe, Operational Health Physics Training

The average energy expended to produce an ion pair is called: 

A) W value 

B) dosimetry constant 

C) ion pair energy 

D) kinetic energy 

E) rest mass 



In a gas filled detector a low voltage potential will increase 

the time required to collect ions produced by radiation 

permitting a large number to be neutralized. This process is 

called: 

A) neutralization 

B) ion leakage 

C) annihilation 

D) recombination 

E) saturation 



A gas-filled detector is collecting 100% of the ion pairs 

produced. It is said to be operating in the ______ region. 

A) recombination 

B) ionization 

C) proportional 

D) limited proportional 

E) geiger-mueller 



A gas-filled detector in which the current is independent of the 

voltage but proportional to the amount of radiation to which the 

instrument is exposed is working in the _____ region. 

A) ionization 

B) recombination 

C) proportional 

D) geiger-mueller 

E) limited proportional 


Moe, Operational Health Physics Training, Page 10-5

In the proportional region, the size of the avalanche in the 

gas-filled detector may be controlled by use of a known and 

stable voltage and use of a: 

A) stable fill gas 

B) quench gas 

C) cylindrical design 

D) large anode 

E) stable saturation current 


For a cylindrical chamber, the field strength at any radius from 

the needle is dependent on the voltage, the radius of the wire 

and the radius of the chamber. The field stregth is very high 

near the wire, but drops off quickly as we move away from the 

wire. At some distance near the wire, the field strength is great 

enough to initiate a cascade. this means the cascade always 

starts the same distance from the wire for a given voltage. For 

a specific voltage the size of the cascade is almost constant. 


A semi-conductor is distinguished from an insulator or conductor 

by its: 

A) boiling point 

B) band gap 

C) conductivity 

D) ductility 

E) thermal abilities 


For semi-conductore and insulators, a gap exists between the 

highest filled electron band (called valence band) and the next 

empty band (called conduction band). This gap is called the band 

gap. Moving an electron into the empty band is not easy. In an 

insulator the gap is large, 5 eV or more, in a semi-conductor the 

gap is in the range of 0.7 - 2.1 eV. 


"Doping" a semi-conductor material involves adding an impurity 

that has: 

A) a loosely bound electron 

B) a lack of electrons in the outer shell 

C) same number of electrons as an insulator 

D) same W value as the semi-conductor 

E) a different decay mode than the 

semi-conductor 


An impurity with a loosely bound electron is called a "donor" 

substance. This donor decreases the band-gap width to some small 

value. Adding phosphorus to silicon reduces the band gap to onlyt 

0.045 eV. Since conduction in this case involves negative charges 

(electrons) the substance is called an n-type semi-conductor. 


An "acceptor" substance in a semi-conductor is a material that 

has: 

A) a loosely bound electron 

B) a vacancy in the outer shell of electrons 

C) same number of electrons as the conductor 

D) same W value as an insulator 

E) a lower resistance to current flow 


An impurity atom does not contain enough outer electrons for 

valence binding. This means that a vacancy now exists in what was 

originally a filled band. This creates a hole in the valence 

band. This positive hole can easily "accept" an electron from a 

nearby atom. This type of impurity is called "acceptor" 

substance. These substances are referred to as p-type 

semi-conductors. 

Moe, Operational Health Physics Training book, Page 10-12

A semi-conductor detector is said to be compensated when it has: 

A) more n-type than p-type impurities 

B) more p-type than n-type impurities 

C) equal number of n-type and p-type impurities 

D) no p-type impurities 

E) no n-type impurities 


If the number of n-type impurities is equal to the number of 

p-type impurities, the material is said to be compensated and the 

substance would be like an intrinsic semi-conductor. In this 

case, the impurities "compensate" for each other. 

Moe, Operational Health Physics Training book, Page 10-12

The secondary emission ratio of a photomultiplier tube is the: 

A) number of gammas generated by bremsstrahlung 

B) number of electrons freed by thermionic 

emission 

C) number of light pulses freed by each incident 

electron 

D) number of electrons freed for each incident 

electron 

E) number of incident electrons that are freed 

by light pulses 


This ratio is also a function of the dynode surface substance, as 

well as the energy if electrons that bombard it. Common dynode 

surface materials are BeO, MgO and Cs3Sb. 


A light pipe is used in a scintillation counter to: 

A) shield the phospher from outside light 

sources 

B) illuminate the meter display 

C) remove excess light from detector 

D) provide a standard source of light for 

calibration 

E) prevent the light from being trapped in the 

phospher 


Lucite and quartz are substances used as light pipes. It is 

placed between the scintillator and photocathode. Used to prevent 

the light from being trapped in the phosphor. Such a device 

doesn't eliminate the need for good optical contacts. 

Moe, Operational Health Physics Training, Pages 10-23

Methods used to reduce the amount or effects of dead time in GM 

counters is: 

1. electronic calculations using resolving time 

2. quench gas 

3. using a smaller detector volume 

4. increasing gas pressure 

5. using shorter count times 

A) 145 

B) 12 

C) 13 

D) 123 

E) 235 


Electronic circuitry is used to calculate the true count rate. 

RM-14SA uses this type of circuit to enable unit to indicate 5 E6 

cpm. Decrease detector volume allows ions needing an electron a 

shorter path to detector wall. Quench gas used to provide +ions 

with a source of electrons. 


You have two beta-gamma gas flow proportional detectors on site. 

One detector (1) is located in a low background building and 

registers 22 cpm background. The other detector (2) is located 

near a radioactive material storage area and registers 3 cpm 

background. The difference in background count rate can be 

explained by the use of __________ on detector (2). 

A) 1 1. shielding 

B) 245 2. counting gas 

C) 13 3. coincident counter 

D) 235 4. temperature 

E) 124 5. detector voltage 


Using more shielding will reduce the background seen by the 

detector. Adding coincident circuit involves adding another 

detector which provides the biggest reduction in background count 

rate. If a count is seen in the coincident detector any counts 

coming from the sample detector are ignored, thus reducing the 

background effects by a factor of almost 10 in this example even 

though the detector is in a higher background. 


For protons and neutrons, most of the interactions in occur in 

the ___ of the ion chamber. 

A) wall 

B) center 

C) proximity of the needle 

D) gas 

E) discriminator 


The secondary radiation produced results in ionization in the 

gas. The problem is then to relate the ions collected in the gas 

to the energy imparted to a unit mass of the wall material. 


The response of a GM survey meter is: 

A) directly proportional to the energy absorbed 

in the sensitive volume 

B) not directly proportional to the energy 

absorbed in the sensitive volume 

C) accurate enough for use in exposure rate 

determination 

D) slow in gamma fields > 100 keV 

E) constant for any energy absorbed in the 

detector volume 


The GM survey meter is not an accurate instrument for exposure 

rate measurement. 


A long counter is encased in a cadmium jacket to: 

A) remove thermal neutrons 

B) provide detector integrity 

C) compensate for tissue-equivalency 

D) provide electrical continuity with detector 

circuits 

E) shield against photon radiation 


Outside wall of the tub is enclosed in a cadmium jacket. This 

jacket absorbs all neutrons with energies < 0.5 eV to remove all 

unwanted thermal neutrons. A brass jacket that provides 

mechanical strength is used to cover the cadmium jacket. 

Moe, Operational Health Physics Training, Pages 12-35

Consider a proportional detector operated at a constant voltage. 

Based only on the statistical fluctuations, which of the 

following fill gases would you expect to have the lowest percent 

resolution? 

A) He with a W value of 41.4 ev/ion pair 

B) Ne with a W value of 36.2 ev/ion pair 

C) Air with a W value of 33.7 ev/ion pair 

D) Ar with a W value of 26.2 ev/ion pair 

E) Xe with a W value of 21.9 ev/ion pair 


As the W value decreases, the number of ion pairs created for a 

given amount of energy deposited in the detector gas increases. 

Based on statistics, the percent resolution decreases, (i.e. 

improves), as the number of charge carriers increases. The 

formuly is 

R = 2.35/sq root of N, where N equals the number of charge 

carriers or ion pairs.

Choose the BEST answer that describes the difference between 

stopping power and LET. 

A) Stopping power is a function of the absorbing 

medium and LET is a function of the charged 

particle 

B) Stopping power includes both radiative and 

collision losses and LET considers only 

collision losses 

C) LET is a function of the absorbing medium and 

stopping power is a function of the charged 

particle 

D) LET is a function of the specification 

ionization of the charged particle and 

stopping power is a function of specific 

ionization of the absorbing medium 

E) LET and stopping power are the same 


According to the ICRU, stopping power includes losses due to 

collisions (ionizations, excitations) and radiative losses 

(bremsstrahlung). LET includes losses due to collisions which in 

turn is energy that will be locally deposited.

Radiation detectors can be operated in which of the following 

modes? 

A) Current and pulse 

B) Pulse and mean square voltage 

C) Current, pulse and mean square voltage 

D) Current and mean square voltage 

E) Current, pulse, and absolute voltage 


Pulse is the most common mode of operation, allowing analysis of 

the energy of the radiation. Current mode is generally used in 

ionization chambers where the event rate in the detector is high. 

The mean square voltage mode is most often used in mixed 

radiation fields to allow discrimination between two types of 

radiation with high event rates where the charge produced by one 

type of radiation is very different from the other. Mixed 

neutron gamma fields are an example.

In a photomultiplier tube with 7 dynodes and a gain of 5 

electrons per dynode, the ratio of the magnitude of the output 

pulse to the primary photoelectron would be approximately: 

A) 35 

B) 2,500 

C) 17,000 

D) 80,000 

E) 1,000,000 


To calculate the output pulse size the gain is raised to the 

power of the number of dynodes. In this case 5^7 or 78,125.

Which of the following is the best method to compensate for high 

background gamma radiation on a 4 pi has flow through ion chamber 

designed to detect tritrium? 

A) Use electronic pulse height discrimination 

B) Shield the detector from gamma radiation with 

a lead housing 

C) Reduce the voltage to the ion chamber to 

prevent the collection of ions created in the 

wall by gamma radiation 

D) Install the instrument in the gamma field 

then calibrate the ion chamber with a known 

concentration of tritrium 

E) Continuously subtract off the gamma 

background with an identical ion chamber not 

sampling tritrium 


Ion chambers do not operate in the pulse mode and cannot 

electronically discriminate between different types of radiation. 

Shielding would most likely not be as practical as answer E. 

Answer D does not allow for changes in the gamma background once 

installed and would most likely be difficult to perform.

A dose of 20 rem from alpha radiation to one Kilogram of tissue 

deposits how many ergs or energy? 

A) 100 

B) 200 

C) 2,000 

D) 20,000 

E) 100,000 


rem = rad x Q, so; 

rad = rem/Q = 20/20 = 1 

(1 rad)(100 erg/gm/rad)(1000 gm/Kg) 

= 100,000 erg/Kg

GM detectors are fairly inefficient for gamma radiation. When 

gamma is detected by a GM tube the mode of interaction is most 

likely due to? 

A) A gamma photon interacting with a detector 

fill gas molecule causing a recoil electron 

which is then detected 

B) A gamma photon interacting with the wall of 

the detector and releasing an electron into 

the fill gas which is then detected 

C) A gamma photon interacting with an air 

molecule outside the GM window, creating a 

recoil electron which then enters the 

detector window and is then detected 

D) A gamma photon interacts with the anode wire 

creating a pulse 

E) GM detectors only detect the beta component 

of a radionuclide and not the gamma component 


The probability of gamma interaction is much greater with a dense 

material such as the metal housing of the GM detector, rather 

than causing an ionization of a un-dense gas.

The efficiency for collecting ion pairs produced in an ionization 

chamber is greater using: 

A) Parallel plate electrodes 

B) Negative feedback 

C) Cylindrical shaped collecting electrodes 

D) A guard ring 

E) Spherical shaped collecting electrodes 


Parallel plate electrodes yields the greatest efficiency for 

collecting ion pairs in an ionization chamber for the methods 

listed above.

The effective Z of tissue is? 

A) 4.7 

B) 5.6 

C) 7.5 

D) 12.3 

E) 16.3 


The effective atomic number of tissue is generally stated as 7.5. 

This value takes into account the Z of the predominant elements 

compromising tissue.

Which planchet material would yield the highest sample count rate 

in a gas filled proportional counter? 

A) Tungster 

B) Copper 

C) Steel 

D) Aluminum 

E) Plastic 


Tungster is the densest material listed. This material will 

result in the most beta and gamma backscatter into the detector.

Which of the following TLD phosphors exhibits an energy response 

most similar to that of tissue? 

A) CaS04:Tm 

B) LiF 

C) Li2B407:Cu 

D) CaF2:Mn 

E) CaS04 


The effective Z of LiB407:Cu is 7.4, and the effective Z of 

tissue is 7.5.

Which of the following reactions is most commonly used for TLD 

monitoring of thermal neutrons? 

A) Li-6 (n, alpha) H-3 

B) Li-6 (n, gamma) Li-7 

C) F19 (n, proton) 019 

D) Ca40 (n, alpha) Ar37 

E) Tm169 (n, gamma) Tm170 


The reaction is Li-6 + n = H3 + alpha + 4.8 MeV

Ultimately, absorbed dose in tissue from alpha, beta, gamma, and 

neutron radiation is due to: 

A) the damage to biological systems via direct 

and indirect effects 

B) the chemical composition of the tissue 

C) the transfer of kinetic energy to electrons 

D) the transfer of energy to atoms or molecules 

E) none of the above since different radiations 

have different interaction modes 


Although alpha, beta, gamma, and neutron radiations have 

different modes of interactions, absorbed dose will eventually be 

determined by the transfer of kinetic energy to electrons.

Which of the following has a density thickness closest to 2 cm of 

water? 

A) 1 cm of Al with a density of 2.7 gm/cm^3 

B) .5 cm of Cu with a density of 8.96 gm/cm^3 

C) .25 cm of Pb with a density of 11.3 gm/cm^3 

D) .1 cm of W with a density of 19.3 gm/cm^3 

E) None of the above 


The density thickness of 2 cm of water = 2 cm x 1 gm/cm^3 = 2 

gm/cm^2. So .1 cm x 19.3 gm/cm^3 = 1.93 gm/cm^2

One coulomb per kilogram in air equals how many roentgens? 

A) 8,700 

B) 3,881 

C) 3,440 

D) 2,580 

E) 1,000 


(1R/2.58 E-4 C/Kg)(1 C/Kg) = 3,881 R

A 1Kg block of ice and a 1 Kg block of lead are exposed to a 1 

Roentgen per hour radiation field. Which object receives a 

greater absorbed dose after one hour if the photon energy is .2 

MeV? 

A) The absorbed dose to both is the same 

B) The block of ice receives a greater dose 

because the interaction coefficient for water 

is smaller than that for lead at this energy 

C) The block of lead receives a greater dose 

because the interaction coefficient for lead 

is smaller than that for water at this energy 

D) The block of ice receives a greater dose 

because the interaction coefficient for water 

is larger than that for lead at this energy 

E) The block of lead receives a greater dose 

because the interaction coefficient for lead 

is larger than that for water at this energy 


The 0.2 MeV photons are much more likely to interact with the 

high density lead than the relatively low density ice.

On a mass basis, which of the following gives the correct 

descending order of the elements found in soft tissue? 

A) Oxygen, Carbon, Hydrogen, and Nitrogen 

B) Hydrogen, Oxygen, Nitrogen, and Carbon 

C) Nitrogen, Carbon, Oxygen, and Hydrogen 

D) Oxygen, Nitrogen, Carbon, and Hydrogen 

E) Nitrogen, Oxygen, Carbon, and Hydrogen 


Oxygen, Carbon, Hydrogen, and Nitrogen is the correct descending 

order of elements found in soft tissue, on a mass basis.

The difference between the energy 1 roentgen deposits in air per 

gram vs the energy 1 roentgen deposits in tissue per gram from 1 

MeV photons is mainly due to: 

A) the difference in density of air vs. tissue 

B) the difference in electron density per unit 

mass of air vs. tissue 

C) the difference in elemental composition of 

air vs. tissue 

D) the difference in quality factor for tissue 

E) the electrical charge of an ion in air vs. 

the electrical charge of an ion in tissue 


Tissue has roughly 10% more electrons per gram than air. This 

mostly accounts for the difference in energy absorbed (87 ergs 

gm^-1 in air and 95 ergs gm^-1 in tissue). In the Compton 

Scatter region of .1 - 5 MeV, electron density per gram is most 

important.

The term rem is a unit of dose equivalent. Which of the 

following is NOT a correct statement? 

A) A rem is the product of absorbed dose and a 

factor which is currently based on the 

collision stopping power in water 

B) A rem can be considered a unit of risk 

relevant to late effects 

C) Rems are used as units for regulatory limits 

D) Rems can be converted to Sieverts 

E) A dose in rems always has measurable, 

reproducible, and observable acute biological 

effects 


The quality factors used to derive dose equivalent for absorbed 

dose do not apply at absorbed dose rates high enough to produce 

these effects.

The process of transferring photon energy to matter is commonly 

called: 

A) ionization 

B) interactions 

C) excitations 

D) stopping power 

E) LET 


The photon interactions of importance in matter are photoelectric 

effect, compton scatter, and pair production.

In the shielding equation I = Io e^-ux, how does the shielding 

thickness x compare if x is calculated using the linear 

attenuation coefficient vs. the mass energy absorption 

coefficient for a 1 MeV photon? (Assume the same transmission 

factor value and shielding material. Neglect any build-up) 

A) The shielding thickness will be about the 

same 

B) The shielding thickness x will be thicker 

using the linear attenuation coefficient vs. 

the mass energy absorption coefficient 

because the linear attenuation coefficient is 

a larger numerical value than the mass energy 

absorption coefficient for a 1 MeV photon 

C) The shielding thickness x will be thinner 

using the linear attenuation coefficient 

because the linear attenuation coefficient is 

a smaller numerical value than the mass 

energy absorption coefficient for a 1 MeV 

photon 

D) The shielding thickness x will be thicker 

using the mass energy absorption coefficient 

because the mass energy absorption 

coefficient is a larger numerical value than 

the linear attentuation coefficient for a 1 

MeV photon 

E) The shielding thickness x will be thicker 

using the mass energy absorption coefficient 

because the mass energy absorption 

coefficient is a smaller numerical value than 

the linear attenuation coefficient for a 1 

MeV photon 


Since the total linear attenuation coefficient is the sum of 

absorption and scattering processes, the mass energy absorption 

coefficient will generally by a smaller numerical value. A 1 MeV 

photon will most likely under go a compton scatter interaction in 

most materials.

Given a uniform disk source of radiation, at what minimum 

distance from the disk source would the a point source formula 

have only about 1% difference from the disk source formula? 

A) .7 diameters 

B) 1 diameter 

C) 2 diameters 

D) 3 diameters 

E) 4 diameters 


At three diameters the exposure rate calculated from a disk 

source approximates the same value as the point source formula.

What would be the most reliable means to quantify an individuals' 

tritium uptake? 

A) Count nasal wipes on shielded gas flow 

proportional counter to estimate the activity 

inhaled 

B) Well counting of a urine sample via NaI 

spectrometer 

C) Whole body counting in a shielded facility 

via GeLi spectrometer 

D) Analysis of urine samples by liquid 

scintillation counter 

E) Analysis of fecal samples by GeLi 

spectrometer 


Tritium is very soluble and readily eliminated in the urine. 

Gamma spectrometers are useless for detecting the low energy beta 

emitted by tritium.

A photon with a linear attenuation coefficient of .0023/cm^0-1 in 

air will travel how far before an interaction occurs? 

A) .0023 cm 

B) 2.3 cm 

C) 45 cm 

D) 230 cm 

E) 430 cm 


The mean free path = 1/u - 1/0.0023 cm^-1

The most abundant elements in soft tissue on a per atom basis 

are: 

A) Oxygen, Carbon, Hydrogen, and Nitrogen 

B) Hydrogen, Oxygen, Carbon, and Nitrogen 

C) Hydrogen, Carbon, Oxygen, and Nitrogen 

D) Oxygen, Hydrogen, Nitrogen, and Carbon 

E) Carbon, Oxygen, Hydrogen, and Nitrogen 


In descending order, Hydrogen, Oxygen, Carbon, and Nitrogen are 

the most abundant elements found in soft tissue on a per atom 

basis.

The buildup factor used in shielding calculations is not a direct 

function of which of the following parameters? 

A) shield thickness 

B) source activity 

C) gamma-ray energy 

D) source geometry 

E) shield material 


Buildup is independent of source activity. All other choices 

will affect photon scatter, therefore buildup.

The buildup factor should only be used: 

A) for photons of energy below 3 MeV 

B) for photons of energy above .5 MeV 

C) in cases where the shield thickness exceeds 3 

relaxation lengths 

D) for situations involving broad beam or "poor 

geometry" 

E) for situations involving narrow beam or "good 

geometry" 


The effect of photon scatter is much greater in broad beam 

geometries than for narrow beam situations.

The half-value thickness for 1 MeV photons in lead is 

approximately 1 cm. A 100 mCi Zn-65 (1.12 MeV/photon) point 

source produces a dose rate of 30 mR/hr at 1 meter. What is the 

exposure rate at 10 cm from this source with the addition of a 5 

cm lead shield? (Assume a buildup factor of 2.1) 

A) 0.02 mR/hr 

B) 93.8 mR/hr 

C) 2.0 mR/hr 

D) 9.4 mR/hr 

E) 200 mR/hr 


I = B Io (1/2)^n / d^2 

I = (2.1) (30 mR/hr) (1/2)^5 / (0.1m)^2 

I = 196.9 mR/hr at 10 cm (0.1 m)

A worker is exposed to 2340 Bq m^-3 (6.3E-8 uCi cm^-3) I-131 for 

4 hours. The DAC for I-131 is 333 Bq m^-3 (9E-9 uCi cm^-3). The 

worker was wearing cotton coveralls, rubber boots and gloves, and 

an air-purifying respirator with charcoal cartridges. How many 

DAC-hours should the worker be assigned? 

A) 0.5 DAC-hours 

B) 1 DAC-hour 

C) 4 DAC-hours 

D) 7 DAC-hours 

E) 28 DAC-hours 


DAC-hours = Airb. Conc./DAC x hours 

DAC-hours = (6.3E-8 uCi cm^-3)/(9E-9 uCi cm^-3) x 4 hr 

= 28 DAC-hrs 

Note: No protection factor for iodine can be taken for 

charcoal cartridges (see 10CFR20, App. A)

BF3 gas filled detectors frequently used in neutron measuring 

instruments provide good discrimination against gamma radiation 

induced pulses because: 

A) B-10 has a high cross section for (n, gamma) 

reactions where the high energy photon causes 

a large pulse compared to those due to 

photons originating outside of the detector 

B) the detectors are operated in the GM voltage 

region and the neutron induced pulses greatly 

exceed the photon induced pulses 

C) the cross section for neutron scattering off 

the BF3 molecule is large and the resulting 

pulse is very large because of the large 

molecule size 

D) the cross section for the (n, alpha) reaction 

for thermal neutrons with B-10 is large and 

the detector is operated in the proportional 

voltage region 

E) the abundant F atoms have a high affinity for 

gamma induced free electrons, thus inhibiting 

the detection of photons 


In proportional counters, alpha particles create a much larger 

output signal due to their mass and double positive charge. The 

alphas produced by the (n, alpha) reaction within the detector 

volume are easily distinguished from any pulses produced by gamma 

photons.

A worker wearing a respirator with a rated protection factor of 

100 for particulates is exposed to a concentration of airborne 

particulate Co-60 at 10 times the DAC for a period of eight 

hours. What is the worker's calculated dose equivalent? 

A) 200 mrem CEDE 

B) 2 mrem CEDE 

C) 200 mrem CDE 

D) 0.1 mrem CDE 

E) 2 mrem CDE 


Since the DAC for Co-60 is based on the stochastic Annual Limit 

on Intake (sALI), one DAC-hr represents 2.5 mrem committed 

effective dose equivalent (CEDE). 

CEDE = (DAC fraction x hrs x 2.5 mrem/DAC-hr)/PF 

= (10 DAC x 8 hrs x 2.5 mrem/DAC-hr)/100 

= 2 mrem

A GM detector with a resolving time of 100 microseconds indicates 

a net sample count rate of 55,540 cpm. The true sample count 

rate is approximately: 

A) 61,200 cpm 

B) 50,830 cpm 

C) 364,000 cpm 

D) 56,060 cpm 

E) 101,660 cpm 


True Ct. Rate = Obs. Ct. Rate/1-(Obs. Ct. Rate)(r) 

= 55,540 cpm/1-(55,540 cpm)(100 usec)(1 sec/1E6 usec)(1 

min/60 sec) 

= 61,206 cpm

A worker has an inhalation intake of 1000 Bq of Class Y Co-60 and 

6000 Bq of Class D I-131. The ICRP 30 stochastic Annual Limits 

on Intake for Co-60 and I-131 are 1E6 Bq and 6E6 Bq respectively. 

Lacking any other specific information, the worker's committed 

effective dose equivalent is properly estimated as: 

A) 2 mrem 

B) 4 mrem 

C) 6 mrem 

D) 8 mrem 

E) 10 mrem 


Calculate the fraction of the ALI received: 

(1000 Bq/1E6 Bq sALI^-1) + (6000 Bq/6E6 Bq sALI^-1) 

= 0.002 sALI 

One sALI = 5,000 mrem CEDE, so: 

0.002 sALI x 5,000 mrem/sALI = 10 mrem

Electrons that are initially at rest are accelerated through a 

voltage potential of 1,000 volts before striking a tungsten 

target. What energy do the electrons have upon striking the 

target? 

A) 1,000 MeV 

B) 10 MeV 

C) 0.1 MeV 

D) 0.001 MeV 

E) 0.511 MeV 


The unit "electron volt" (eV) is used to quantify radiation 

energy. One eV is attained when accelerating an electron through 

an electrical potential difference of one volt. (More 

accurately, one eV is the energy required to move an electron 

through a one volt potential difference. See "Operational Health 

Physics Training", H.J. Moe, Argonne National Laboratory, or 

"Introduction to Health Physics", Second or Third Edition, H. 

Cember, Pergamon Press.) 

In this problem, each electron would attain an energy of 1,000 

eV, or 1 keV, or 0.001 MeV.

The dead time for proportional counters is approximately: 

A) 5 nanoseconds 

B) 0.5 microseconds 

C) 50 microseconds 

D) 100 microseconds 

E) 0.5 milliseconds 


Since proportional counters have such short dead times, 

correcting observed count rates for high activity samples is not 

nearly as significant as such corrections for GM detectors. GM 

counter dead times may exceed 100 microseconds.

For general area radiation surveys, the NRC specifies measuring 

dose rates at what distance from a radiation source or a surface 

the radiation penetrates? 

A) 18 inches 

B) 30 inches 

C) 18 centimeters 

D) 30 centimeters 

E) 50 centimeters 


10 CFR 20 defines Radiation and High Radiation areas in terms of 

potential individual doses at a distance of 30 cm (roughly 12 

in.) from radiation sources or surfaces the radiation penetrates. 

Very High Radiation Areas are determined based on dose rates at 1 

meter.

A sample with mixed alpha and beta emitting nuclides is counted 

with a gas flow proportional counter at the alpha voltage (A) and 

at the beta voltage (B). The alpha and beta count rates, 

respectively, may be estimated from these count rates as: 

A) B-A and B 

B) A and B-A 

C) B-A and A 

D) A and A-B 

E) A-B and A 


"A" represents the detector voltage at which only counts due to 

alpha radiation will be detected. "B" represents a higher 

detector voltage at which both alpha and beta radiation will be 

detected. The count rate at voltage "A" is simply the alpha 

count rate. Subtracting the count rate at voltage "A" from the 

higher count rate at voltage "B" will yield the count rate due to 

beta radiation only.

For a gas filled detector operating in the GM region, the 

detector output pulse amplitude: 

A) is approximately proportional to the energy 

of the radiation entering the detector. 

B) will increase proportionally with detector 

wall density-thickness. 

C) is independent of the type and energy of the 

radiation entering the detector. 

D) is dependent on the voltage applied to the 

detector. 

E) is proportional to the number of primary ion 

pairs produced in the fill gas. 


Any number of ionizing events in the detector fill gas will cause 

complete detector discharge. The output pulse amplitude is 

therefore independent of the type and energy of radiation 

entering the detector, and there is no proportionality with 

respect to radiation energy or number of primary ion pairs 

produced. In the GM region, output pulse amplitude is not 

significantly affected by detector applied voltage (as indicated 

by the "flat" GM region of the six-region curve). 

See Gollnick, 3rd Ed., p. 254

A detector yields a FWHM of 3 keV for the primary I-131 

photopeak. The percent resolution of the detector at this energy 

is: 

A) 0.008% 

B) 0.08% 

C) 0.8% 

D) 8.0% 

E) 80% 


% Res = (FWHM/photopeak energy) x 100% 

= (3 keV/364.5 keV) x 100% 

= 0.82% 

If you didn't know the I-131 peak energy, an educated guess of 

somewhere between 100 and 2000 keV would yield % resolution 

values between 0.15 and 3. "C" is the only choice in this range.

For a typical NaI scintillation detector, the energy resolution 

for a 662 keV Cs-137 gamma photon is approximately: 

A) 7% 

B) 15% 

C) 25% 

D) 40% 

E) >50% 


Memorize this or remember that the FWHM for the Cs-137 photopeak 

on a NaI system is roughly 50 keV. Since % resolution = 

(FWHM/Photopeak energy) x 100%, a 50 keV FWHM yields an energy 

resolution of 7.5%. 

See Gollnick, 3rd Ed., p.270

An HPGe detector is advertised as being 120% efficient. Which of 

the following best explains how the detector can be greater than 

100% efficient? 

A) Each gamma interaction within the detector 

volume produces multiple output pulses. 

B) Germanium detector efficiencies are commonly 

stated in terms of relative efficiency as 

compared to a 3 x 3 inch NaI(Tl) detector. 

C) The detector operating voltage is so high 

that output pulses are amplified by a factor 

of 1.2. 

D) The germanium crystal is 120% larger than a 

3 x 3 inch NaI(Tl) crystal. 

E) The manufacturer has produced a germanium 

crystal that is 1.2 times as dense as 

standard germanium. 


The 3 x 3 inch sodium iodide scintillation detector is used as an 

industry standard by which other gamma spectrometer detectors are 

compared. Germanium detectors are less efficient than 

comparably-sized NaI(Tl) detectors. 

See Gollnick, 3rd Ed., p. 273

What is the approximate efficiency for the radioiodines on an 

activated charcoal filter at the appropriate flow rate for the 

specific instrument used? 

A) 5% 

B) 25% 

C) 75% 

D) 95% 

E) 99% 


If the flow rate approaches 5 liters per minute, the efficiency 

can be as high as 98%.

What is the approximate efficiency for the detection of Xe-133 on 

activated charcoal? 

A) 1% 

B) 10% 

C) 50% 

D) 95% 

E) 99% 


The efficiency is usually less than 1%. This radioisotope of 

xenon is a byproduct of the fission process in a nuclear reactor 

and is used in nuclear medicine as a lung scanning agent.

The largest respirable particle is considered to be: 

A) 100 microns 

B) 30 microns 

C) 10 microns 

D) 1 micron 

E) 0.1 microns 


Additionally, the most difficult particle sizes to filter are 0.2 

to 0.5 microns.

A worker wearing a supplied-air full-face respirator and cotton 

coveralls worked in an area where the exposure without protection 

would have been 2,000 DAC-hours of I-131 and 1,000 DAC-hours of 

tritium. If the protection factor of the respirator is 1,000, 

the approximate intake corresponds to: 

A) 3,000 DAC-hours 

B) 1,000 DAC-hours 



E) 3 DAC-hours 


Since the maximum protection factor that can be taken for tritium 

is 2 (10 CFR 20, Appendix A), the calculation is as follows: 

(2000 DAC-hrs/1000) + (1000 DAC-hrs/2) = 502 DAC-hrs

A worker wearing a respirator with a rated protection factor of 

50 is exposed to a concentration of long-lived airborne 

particulate activity at 10 times the DAC for a period of 10 

hours. Allowing for the respiratory protection, what is the 

worker's calculated exposure? 

A) 500 DAC-hours 

B) 100 DAC-hours 



E) 0.2 DAC-hours 


(DAC fraction/PF) x time (hrs) = DAC-hrs 

10/50 x 10 hrs = 2 DAC-hrs

Which of the following is NOT a basis used for choosing 

environmental sampling locations? 

A) meteorological data 

B) population density 

C) hydrological data 

D) locations of main intakes of water from 

surrounding rivers 

E) geological data 


Population density is a factor considered when choosing the 

location for the construction of a facility, but is not as 

important as the other listed factors when establishing sampling 

locations once the facility is operational.

The term solubility or transportability, when applied to the 

metabolism of radionuclides, refers to the: 

A) metabolic breakdown of a radionuclidecontaining 

compound which allows its 

incorporation into body tissues 

B) solubilization of a radionuclide-containing 

compound by means of hydration, ion exchange, 

or esterification reactions 

C) translocation dissimilation of a 

radionuclide-containing compound by means of 

biological-chemical action such as enzymatic 

attachment and catabolism 

D) property of a radionuclide-containing 

compound which results in its transfer across 

body membranes 

E) translocation of a radionuclide-containing 

compound from one point to another under 

conditions of physiological dysfunction 


The more soluble, or transportable, a compound is, the more 

likely it is to be taken up systemically in the body and 

transferred to a number of tissues. An example of a very 

"transportable" compound in the body is tritium oxide. A 

low-transport compound may be one containing heavy metals, such 

as plutonium, that tends to adhere to the bone surfaces.

A worker is exposed to 2,340 Bq/cubic meter (6.3 E-8 

microcuries/ml) I-131 for 4 hours. The DAC for I-131 is 333 

Bq/cubic meter (9 E-9 microcuries/ml). The worker was wearing 

cotton coveralls, rubber boots and gloves, and an air-purifying 

respirator with particulate combination cartridges. Which one of 

the following gives the closest number of DAC-hours that you 

would assign the worker? 

A) 28 DAC-hours 

B) 7 DAC-hours 


D) 1 DAC-hour 

E) 0.5 DAC-hour 


The respirator provides a protection of 1 for iodine (see 10 CFR 

20, App. A). 

(DAC fraction/PF) x time (hrs) = DAC-hrs 

[(6.3 E-8/9.0 E-9)/1] x 4 hrs = 28 DAC-hrs

Which is the major factor in considering the milk-food chain when 

relating release of activity to the air and the dose to the 

population? 

A) short period of time between cow exposure and 

retail marketing of milk 

B) large volume of air the cow breathes daily 

C) large concentration factor between air and 

milk due to the large pasture area a cow 

traverses to obtain food 

D) large quantity of milk consumed by adults 

E) large quantity of milk consumed by children 


This pathway is specified in NRC Regulatory Guide 1.109 as a 

predominant ingestion exposure pathway. Not only is the large 

grazing area a factor, but also the large volume of food that the 

cow consumes.

A research facility that uses tritium in levels that may pose an 

internal radiation hazard to workers is usually required by the 

NRC to have as part of their radiation safety program the 

following: 

A) whole body counting of potentially exposed 

workers 

B) air sampling and analysis for tritium in the 

workplace environment 

C) blood tests of potentially exposed workers 

D) tritium urine analysis of potentially exposed 

workers 

E) tritium breath analysis of potentially 

exposed workers 


Urinalysis with frequent sampling periods and liquid 

scintillation counting is necessary to properly assess internal 

dose to personnel from tritium. Since tritium is an isotope of 

hydrogen, the body assimilates it in its oxide form much the same 

as water.

The most important types of environmental monitoring to perform 

soon after accidental release of radioactive materials to the 

outside air would be: 

A) airborne concentrations and sediment sampling 

B) direct radiation levels and water sampling 

C) water sampling and vegetation sampling 

D) direct radiation levels and airborne 

concentrations 

E) silt and broad-leaf vegetation sampling 


Since it is specified that the measurements will be taken soon 

after release, the radioactive material may still be airborne. 

Since exposure pathways may include both internal and external 

factors, measurements must be taken for both.

Indoor unattached radon decay products are commonly measured 

using all of the following EXCEPT: 

A) diffusion battery 

B) cyclone precollectors 

C) electrostatic collectors 

D) diffusion tubes 

E) screen samples 


The unattached radon decay products would not be large enough to 

be collected with a cyclone precollector.

The fraction of unattached radon decay products in the air 

depends upon all of the following EXCEPT: 

A) condensation nuclei concentration 

B) particle size distribution 

C) radon concentration 

D) diffusion coefficient of Po-218 

E) room surface plateout rate 


The key word in the question is "fraction". The concentration of 

radon decay products in the air will depend upon the radon 

concentration, but the fraction is independant of the radon 

concentration.

The primary purpose of a routine tritium urinalysis bioassay is 

to: 

A) monitor and assign doses to workers at 

regular intervals in order to provide 

feedback for determining the remaining annual 

allowable dose 

B) verify doses estimated by the airborne 

concentrations and workplace stay times 

C) set a bioassay time interval capable of 

detecting 100 mrem committed effective dose 

equivalent 

D) comply with ANSI N477.1 

E) assess the effectiveness of administrative 

and physical controls of the radiation 

protection program for tritium 


A routine bioassay program should be designed to provide a 

quality assurance check on the effectiveness of the radiation 

protection program. Event-driven bioassays are performed to 

determine internal doses to workers from a suspected uptake.

Why is the thumb rule formula X = 6CEN valid over a wide range of 

photon energies? 

A) The mass attenuation coefficients for most 

materials are linear over the compton scatter 

region for photon energies of 0.1 - 2 MeV 

B) The mass energy absorption coefficients for 

most materials are linear over the compton 

scatter region for photon energies of 0.1 - 2 

MeV 

C) The photoelectric effect is linear for most 

materials for photon energies of 0.1 - 2 MeV 

D) The mass energy absorption coefficient for 

air is linear over most of the compton 

scattering region for photon energies of 0.1 

- 2 MeV 

E) The thumb rule is only a rough approximation 

valid to +/- 70% of the actual values 


In the formula X = 6CEN, recall that: 

X = exposure rate at 1 ft from a point source (R/hr) 

C = source activity (Ci) 

E = photon energy (MeV) 

N = photon abundance (photons/disintegration) 

The thumb rule is valid to within 20% of actual values for photon 

energies of 0.1 - 2 MeV. The probability of compton scatter is 

virtually independant of the "Z" (atomic number) of the absorber.

If an isotope has a DAC of 1 E-8 microcuries/ml and it will be 

released through a stack with a flow rate of 1 E 6 liter/hr, how 

many microcuries of the isotope can be released at a constant 

rate in one day without exceeding the DAC? 

A) 240 

B) 120 

C) 24 

D) 1.0 

E) 0.4 


1 E-8 uCi/ml x (1 E6 L/hr x 24 hr x 1 E3 ml/L)= 

240 uCi

A low energy alpha detector is usually effective 

if the detector is _______ distant from the source. 

A) 1/4 inch 

B) 1/2 inch 

C) 1 inch 

D) 1 1/2 inches 

E) 2 inches 


Low energy alpha particles can only travel 

less than 1/2 inch in air. Therefore, one must 

be closer than this to detect them.

A sample of I-131 (half life = 8 days) is kept for 80 days, at 

which time the activity is 1 microcurie 

What was the original activity? 

A) 2.0 millicurie 

B) 1.0 millicurie 

C) 1.5 millicurie 

D) 3.5 millicurie 

E) 4.0 millicurie 


After 10 half lives the remaining activity is approximately 

1000th of the original amount. Therefore if there was 1 

microcurie left after 10 half lives then there must have been 

1000 times more to start with. Hence 1 microcurie x 1000= 1 

millicurie.

A sample of radioactive material is reported to 

contain 2000 picocuries of activity. Express this value as 

disintegrations per minute. 

A) 370 dpm 

B) 900 dpm 

C) 3770 dpm 

D) 4440 dpm 

E) 5320 dpm 


dps = 2000 piCi x 10^-12Ci/pi x 3.7x10^10 dps/Ci 

dpm = 74 dps x 60 sec/min 

= 4440 dpm 

Remember to convert to disintegrations per minute not 

DISINTEGRATIONS PER SECOND !

A sample of wood from an ancient forest showed 

93.75% of the Carbon-14 decayed. How many half 

lives did the carbon go through ? 

A) 1 

B) 2 

C) 3 

D) 4 

E) 5 


1 half life = 50% remaining 

2 half lives = 25% remaining 

3 half lives = 12.5% remaining 

4 half lives = 6.25% remaining

A worker accidentally ingested one millicurie of 

tritium. Tritium has a half life of 12 years. The number of 

disintegrations per second in the worker's body is: 

A) 3.7 E7 dps B) 2.5 E3 dps 

C) 1.7 E8 dps D) 2.2 E6 dps 

E) 3.7 E10 dps 


By definition, 1 millicurie = 3.7 E7 dps. Dps 

stands for disintegrations per second. Therefore if one 

millicurie of tritium is ingested the number of disintegrations 

per second must be 3.7 E7.

Calculate the absorbed dose rate produced in bone (f= 0.922) by a 

1MeV gamma radiation source which produced an exposure rate of 

0.5mr/hr. 

A) 0.37 mr/hr 

B) 0.4 mr/hr 

C) 0.32 mr/hr 

D) 0.004 mr/hr 

E) 0.002 mr/hr 


D = 0.87 x f x X (in rads) 

= 0.87 x 0.922 x 5 E-4 mr/hr 

= 4 E-4 Rads/hr 

= 0.4 mr/hr 

Where D = absorbed dose rate

Conjunctivitis may result from a welding arc due 

to: 

A) Intense visible light radiation 

B) UV radiation 

C) IR radiation 

D) Soft x-ray radiation 

E) Spark 


The wavelengths responsible for conjunctivitis are 270-280 nm in 

the ultraviolet area of the electromagnetic spectrum.

Eight curies of tritium has a disintegration rate of: 

A) 12.5 E4 dps B) 2.96 E11 dps 

C) 2.5 E7 dps D) 4.8 E11 dps 

E) 7.4 E10 dps 


By definition, 1 Ci = 3.7 E10 disintegrations 

per second therefore 8 curies would have: 

8 Ci x 3.7 E10 dps/Ci = 2.96 E11 dps

Eventually, charged particles give up their energy to the 

surrounding medium. In the case of the alpha particle, it 

becomes (a): 

A) Proton 

B) Neutron 

C) Tritium 

D) Helium 

E) Deuteron 


An alpha particle consists of 2 neutrons and 2 

protons carrying two positive charges. It absstracts two 

electrons from the surrounding atoms and becomes a helium atom.

Gamma radiation produces ionization by: 

A) Photoelectric effect, compton effect, pair 

production 

B) Photoelectric effect, compton effect, 

bremsstrahlung 

C) Bremsstrahlung, photoelectric effect 

D) Excitation, photoelectric effect, pair 

production 

E) Excitation and bremsstrahlung 


Absorption of gamma ray photons occurs primarily by the 

photoelectric effect, compton effect and pair production.

Gamma rays get their energy from: 

A) Electrons outside the nucleus 

B) Nuclear disintegration 

C) Cosmic rays that change as enter the 

atmosphere 

D) High energy meson particles 

E) Braking radiation 


Gamma rays are similar to X-rays but differ in origin and 

wavelength. Gamma rays get their energy from nuclear 

disintegration while X-rays are produced from dislodging inner 

electrons.

Given a reading of 100mr/hr, gamma, at 10 feet, 

what would be the reading at 2 feet assuming a 

point source geometry? 

A) 6400 mr/hr 

B) 2500 mr/hr 

C) 5000 mr/hr 

D) 3000 mr/hr 

E) 2200 mr/hr 


Apply the inverse square law: (r2/r1) = (d1/d2)^2 

r2 = 100 mr/hr x (10/2)^2 = 2500 mr/hr 

Where r1=distance1; r2=distance2 

d1=exposure rate1; d2=exposure rate2

What is the usual unit of measurement for laser radiation? 

A) J/cm2 or W/cm2 

B) H/cm2 or E/cm2 

C) g/cm2 or m/cm2 

D) J/min or W/min 

E) cm2/g or mg/cm2 


Normally equated to the aperture of the eye, i.e. 7 mm, the 

limits of the laser are normally expressed as joules/cm2 or 

watts/cm2.

If the HVL of Pb for Cobalt-60 gamma radiation is 11 mm, the 

thickness of Pb that would reduce a narrow beam of Cobalt-60 

gamma rays to 1/32 its original value is _____________: 

A) 352 mm 

B) 0.34 mm 

C) 2.91 mm 

D) 55 mm 

E) 0.5 mm 


1/32 is equal to (1/2)^5. Therefore it takes 5 

HVL's to accomplish a reduction of 1/32. Hence, 

5 x 11 mm = 55 mm.

Normal background radiation exposures are partially due to 

ingestion/inhalation and subsequent accumulation in the thyroid 

of which of the following isotopes? 

A) Strontium-90 

B) Cesium-137 

C) Iodine-131 

D) Uranium 

E) Krypton-85 


Iodine has a half life of eight days and collects in the thyroid 

gland. Uranium accumulates in the lung and kidney, Strontium 

accumulates in the bones.

One RAD is equal to : 

A) 100 ergs/gram 

B) 0.1 curies 

C) 3.14 rems 

D) 0.87 Roentgen 

E) 0.98 rem 


The RAD is a special unit for absorbed dose and is equal to 100 

ergs/gram.

Plutonium, taken into the circulatory system, will deposit in 

what areas of the body? 

A) Bone 

B) Liver 

C) Kidney 

D) Thyroid 

E) Nasopharnyx 


Soluble plutonium deposits mainly in the bones. 

The insoluble forms remain in the lungs.

Sealed sources should be tested for leakage at 

least: 

A) Weekly 

B) Monthly 

C) Quarterly 

D) Semiannually 

E) Annually 


All sealed sources should be checked for leaks 

semiannually under NRC RAM licenses.

The average person contains about 0.1 microcuries of K-40 (half 

life = 1.27 E6 years). How many dps is this? 

A) 3.7 E4 dps B) 3.7 E3 dps 

C) 4.6 E6 dps D) 2.6 E3 dps 

E) 1.3 E6 dps 


By definition 1 microcurie = 3.7 E4 dps, 

therefore, 0.1 microcurie = 3.7 E3 dps.

The becquerel is a measure of: 

A) The rate of disintegration of a radioisotope 

B) The ionizing power of a radioisotope 

C) The quantity of a radioisotope 

D) The activity of a radioisotope 

E) The dose equivalent from radiation 


The becquerel is a unit in the S.I. system used to express the 

activity of a radioisotope.

The current OSHA standard for far field exposure 

to microwave radiation averaged over any 0.1 hour period is: 

A) 0.01 W/cm2 

B) 0.1 W/cm2 

C) 1.0 W/cm2 

D) 10 W/cm2 

E) 100 W/cm2 


The value is normally listed as 10 mw/cm2.

The electromagnetic radiation produced by the 

rapid deceleration of charged particles is called: 

A) Compton effect protons 

B) Bremsstrahlung 

C) Light 

D) Angular radiometric release 

E) Pair production 


The classic definition of Bremsstrahlung is: the 

electromagnetic radiation produced by the rapid 

deceleration of charged particles.

The fraction of atoms which undergo decay per unit time is: 

A) Half life 

B) Activity 

C) Decay constant 

D) Effective half life 

E) Effective removal constant 


The decay constant is expressed in disintegrations per second.

The most common exposure to ultraviolet radiation is from: 

A) Welding 

B) Germicidal lamps 

C) Direct sunlight 

D) Black lights 

E) X-ray diffraction units 


Sunlight is the major source of exposure to ultraviolet light.

The portion of the body most susceptible to laser damage is: 

A) Gonads 

B) Eye 

C) Skin 

D) Blood cells 

E) Bone 


Damage can occur to the skin but it is of secondary importance to 

the eye.

The radon daughters inhaled during uranium mining are normally 

deposited in what part of the human body? 

A) Bone 

B) Kidneys 

C) Liver 

D) Lungs 

E) Thyroid 


The most important radon daughters are Bi, Po, Pb. They are 

deposited in the lung when inhaled, where they may lead to lung 

cancer.

The gray is a quantity used to express: 

A) Energy deposited per unit weight 

B) Ionization in air 

C) Biological effectiveness 

D) Ionization in air due to gamma radiation 

E) Specific ionization 


The gray is the SI quantity of absorbed dose, and is expressed in 

units of J/kg. One gray = 100 rad.

The roentgen is a unit used to express: 

A) The energy deposited in a unit weight of 

material 

B) The ionization in air due to all radiation 

types 

C) The biological effectiveness of gamma 

radiation 

D) The ionization in air due to gamma radiation E) The specific 

ionization of a material 


The measure of ionization produced in air by X-ray or gamma 

radiation is called the Roentgen (R).

A very thin windowed Geiger-Mueller detector 

can detect which of the following radiations? 

A) Alpha 

B) Beta 

C) Gamma 

D) Alpha, beta, gamma 

E) Beta, gamma 


The thin windowed GM counter can detect all three types of 

ionizing radiation.

Three half value layers of lead will produce a 

reduction ________ fold reduction in x-rays. 

A) 4 

B) 5 

C) 6 

D) 8 

E) 16 


A half value layer produces a reduction of 1/2. 

Therefore 1/2 x 1/2 x 1/2 = 1/8 for a reduction 

factor of 8.

What is the charge produced in a 250 cc free air 

ionization chamber by an exposure of 100 mr? 

A) 25 esu 

B) 30 esu 

C) 100 esu 

D) 250 esu 

E) 300 esu 


If 1 R = 1 esu/cc, then how many esu's=0.1R ? 

X = (0.1 R) x (1 esu/cc/R) x (250 cc) = 25esu 

Where R= Roentgen; esu= Electrostatic unit

What is the most common ionizing radiation hazard associated with 

antistatic devices? 

A) Alpha 

B) Beta 

C) Gamma 

D) Neutron 



Antistatic devices often contain Polonium-210, an alpha emitter. 

It is a hazard only if ingested or inhaled.

What is one of the special units used to express 

activity of radioactive materials? 

A) Microrad 

B) Curie 

C) Gamma 

D) Dose 

E) Becquerel 


The curie is a unit of activity. One curie 

equals 3.7 E10 disintegrations per second. The 

SI unit is the Becquerel. One becquerel is equal to one 

disintegration per second.

What type of radiation presents the greatest 

internal hazard? 

A) Alpha 

B) Beta 

C) Gamma 

D) Positron 

E) Neutron 


Alpha particles can cause extensive ionization in tissues, due to 

their large mass and high LET. They are shielded by the skin as 

an external source.

When a charged particle strikes an electron 

knocking it out of its orbital, creating an ion 

pair, it is called: 

A) Indirect ionization 

B) Direct ionization 

C) Specific ionization 

D) Linear energy transfer 

E) Spallation 


Direct ionization is ion pair formation by the incident charged 

particle.

Which instrument would you use to locate a lost, 

small radium source? 

A) Cutie pie 

B) Condenser R meter 

C) Geiger-Mueller meter 

D) NaI scintillation counter 

E) Proportional counter 


The GM meter would be effective but since the radium source would 

be producing gamma rays the most sensitive meter would be the 

scintillation counter.

Which of the following is a Beta emitter? 

A) Strontium-90 

B) Americium-241 

C) Thorium-232 

D) Uranium-238 

E) Neptunium-237 


The heavier elements Am, Th, U, and Np are all alpha emitters, 

Strontium is a beta emitter.

Which of the following radionuclides in soil is 

major contributor to genetically significant radiation exposure? 

A) Carbon-14 

B) Tritium 

C) Radium-226 

D) Potassium-40 

E) Argon-41 


Potassium-40 is present in significant quantities soil.

Which one of the following types of radiation has the highest 

quality factor? 

A) Beta particles 

B) Gamma radiation 

C) Alpha particles 

D) High speed neutrinos 

E) Neutrons of unknown energy 


Quality factors measure linear energy transfer. 

Since alpha particles are large, they would have a large quality 

factor. Beta particles are much 

smaller and hence a smaller Q.F..

Production of a positron is the result of the conversion of a: 

A) Neutron to a proton 

B) Proton to a Pi meson 

C) Proton to a neutron 

D) Proton to an electron 

E) Electron to a proton 


When a proton converts to a neutron it releases a positively 

charged particle called a positron.

What will the activity of 10 Ci of I 131 be in 60 days? (Given 

that the halflife of I 131 is 8 

days). 

A) 5.5 mCi 

B) 55 mCi 

C) 550 mCi 

D) 37.5 mCi 

E) 375 mCi 


Activity= Ci x e^-(ln2/halflife x days) 

= 10 Ci x e^-(ln2/8 x 60) 

= 10 x e^-(0.693/8 x 60) 

= 10 x e^-(5.20) 

= 10 x (0.0055) = 55 mCi

How long will it take for 20 Ci of Polonium 210 to decay to less 

than 1 mCi? The halflife of Polonium 210 is 138 days. 

A) 3.0 years 

B) 5.4 years 

C) 9.2 years 

D) 10.1 years 

E) 12.3 years 


Activity at t= Activity at t(0) e^-(ln2/t1/2 x days) 

A(t)=A(0) e^ -0.693/138 x Days 

1.0 mCi = 20 Ci e^ -(0.693/138 x Days) solve for Days 

Days= -(ln 1 E-3/20) x (138/0.693) 

Days= 9.9 x 199 = 1970 days = 5.4 years

Radon has been estimated to account for 5k-20k lung cancers in 

the United States alone. Controlling radon exposures in a 

building means that __________ of the building is to be avoided. 

A) Pressurization 

B) Congestion 

C) Depressurization 

D) Dilution ventilation 

E) Open ventilation 


Depressurization of the building would tend to draw radon gas in 

from the surrounding soils. Depressurization therefore is to be 

avoided.

Which of the following control methods would not be effective in 

controlling exposure to radon? 

A) Mechanical air filters 

B) Building pressurization 

C) Increase dilution ventilation in building D) Increase 

natural ventilation in building 

E) Sealing foundation cracks 


Since radon is a gas, mechanical filtering devices would not be a 

good control method. Pressurizing the building, increasing 

dilution ventilation and natural ventilation would be methods for 

controlling radon gas exposure.

Two cost effective means available to test for radon gas in a 

building are: 

A) Geiger-Mueller Counter, alpha track detector 

B) Scintillation counter, charcoal canister 

C) Proportional counter, alpha track detector 

D) Alpha track detector, charcoal canister 

E) E-Perm, proportional counter 


Radon gas is an alpha emitter. Since ambient levels are 

extremely low, tradtional grab sampling techniques are very 

expensive. The two most cost effective methods for measuring 

radon in buildings are charcoal canister and alpha track 

detector. Both devices are left exposed to the ambient air in 

the building for 3-7 days and 2-4 weeks respectively.

A classic type interaction occurs when a positron and an electron 

interact to produce 2 photons each with an energy of 511 KeV. 

The reaction is called: 

A) Compton effect 

B) Annihilation 

C) Fusion 

D) Electron fission 

E) Pair production 


A positron is a particle with the same mass as an electron but 

carries a positive charge. When a positron collides with an 

electron both particles are annihilated and converted to two 

photons of energy, each with 511 KeV.

Higher atomic weight (Z) elements tend to release ________ upon 

radioactive decay. 

A) Beta particles 

B) Alpha particles 

C) Gamma photons 

D) X-rays 

E) Positrons 


High Z elements tend to release alpha particles upon radioactive 

decay. The lower Z elements tend to produce beta particles.

The SI unit replacing the rad is the: 

A) Coulomb per kilogram 

B) Gray 

C) Rem 

D) Lambert 

E) Sievert 


The gray is the SI unit replacing the rad. One gray is 

equivalent to 100 rad or 1 joule/kilogram. The gray is denoted 

by Gy.

Under the SI system there have been a number of 

changes in terminology in radiation protection. The SI term for 

activity is the: 

A) Gray 

B) Foot-lambert 

C) Becquerel 

D) Sievert 

E) Coulomb per Kilogram 


The becquerel is the unit that is replacing the disintegration 

per second. One becquerel is one disintergration per second and 

is 2.703 E-11 Ci. 

The becquerel is denoted by Bq.

The SI replacement unit for the rem is the: 

A) Gray 

B) Becquerel 

C) Sievert 

D) Rad 

E) Coulomb per Kilogram 


The sievert is the SI unit that replaces the 

rem. One sievert is equal to 100 rem, i.e. 0.01 Sv is equivalent 

to 1.0 rem.

Smokers have increased exposure to several radionuclides relative 

to non-smokers. This increased dose to the lungs is due to the 

presence of ____ in tobacco. 

A) Polonium-210 and Lead-210 

B) Thorium-232 

C) Radon-222 

D) Radium-226 

E) Potassium-40 


Polonium 210 and lead 210 are thought to be responsible for a 

three fold dose equivalent rate for the lungs of smokers versus 

those of non-smokers.

When ionizing radiation impacts a biological molecule a(n) 

________ is ejected. 

A) Orbital electron 

B) Nulcear electron 

C) Neutron 

D) Proton 

E) Beta particle 


Ionization is the ejection of an orbital electron. This ejection 

results in formation of an ion pair i.e. a positive ion that the 

electron left and a negative ion that the electron became.

When ionizing energy ejects an electron from a 

water molecule it makes a H2O+ ion, when an electron is added to 

a water molecule it makes H2O - . H2O - then decomposes into: 

A) Carbonium ions 

B) Superoxide ions 

C) Acetyl CoA 

D) Free radicals 

E) Electrically neutral hydrogen 


H2O - decomposes and releases a hydrogen radical. A radical 

contains an unpaired electron. They are short lived and very 

reactive. H2O+ decomposes and releases a hydroxyl radical. 

These radicals can interact with biological molecules. This is 

one of the theories concerning the possible mechanisms of damage 

for ionizing radiation.

Cobalt 60 has a half life of 5.27 years. What amount of a 0.100 

gram sample will remain after 1.0 years? 

A) 8.8 g 

B) 0.876 g 

C) 0.0876 g 

D) 0.98 g 

E) 0.098 g 


Rate constant k=0.693/half life =0.693/5.27= 0.132/y 

|frac x orig= 

log (No/N)=kt/2.3 | 

=(0.132) x (1.0 y)/2.3 |0.876 x 0.1 = 

log(No/N)=0.0573 | 0.0876 g 

log(N/No)=-0.0573 | 

N/No =0.876 (fraction remaining) |

What is the decay constant for Carbon-14 

given that the half life is 5770 years? 

A) 0.120/year 

B) 0.0012/year 

C) 1.2 E-4/year 

D) 1.2/year 

E) 12/year 


k the decay constant is related to 

half life via the equation: 

k=0.693/half life 

k=0.693/5770 years 

k=0.00012/year equivalent to 1.2 E-4/year

One of the processes that increases the neutron/proton ratio in a 

nucleus involves the conversion of a proton to a neutron. This 

process is called: 

A) Beta minus decay 

B) Electron capture 

C) Fission 

D) Fusion 

E) Isomeric transition 


Electron capture is sometimes called K capture because it 

involves the nucleus "capturing" an electron from the K or L 

shell. The electron converts one of the protons to a neutron and 

the neutron/proton ratio is increased.

A scintillation counter takes advantage of properties of 

materials that ________ after being exposed to energy from 

radioactive sources. 

A) Emit fast neutrons 

B) Fluoresce 

C) Undergo beta decay 

D) Undergo alpha decay 

E) Undergo fission 


Zinc sulfide and Sodium Iodide have been used as detector 

material in scintillation counters. These materials emit bursts 

of light after exposure to energy from radioactive sources. The 

bursts of light are multiplied in intensity and counted. The 

count is a measure of radioactivity.

In a Geiger-Muller counter, gammas and x-rays pass through a 

chamber containing argon. The argon atoms are _______ in the 

chamber and move through an electric field. 

A) Converted to alpha particles 

B) Left unchanged 

C) Ionized 

D) Annihilated 

E) Activated 


The argon atoms are ionized to Ar+. The chamber 

where the ionization takes place is in an electric field of 

1000-1200 volts. The positively charged argon ions cause an 

avalanche of ions to reach the detector anode as a pulse. This 

pulse is amplified and translated into a count rate, and the 

clicking sound heard when using the instrument.

Radioactive decay is said to be first order decay. It is also 

__________ temperature. 

A) Dependent on 

B) Independent of 

C) Dependent on enthalpy and 

D) Dependent on entropy and 

E) Dependent on high 


Radioactive decay is first order decay and is independent of 

temperature.

Radon-222 has a half life of 3.8 days. What will the activity be 

of 1.0 mCi of radon 222 after 15.2 days? 

A) 0.05 mCi 

B) 0.5 mCi 

C) 0.62 mCi 

D) 0.062 mCi 

E) 0.125 mCi 


One solution: 

One half life results in decrease of 1/2 in the activity of the 

radon 222. How many half lifes is 15.2 days ? 15.2/3.8 = 4 half 

lifes 

4 half lifes = 1/2 x 1/2 x 1/2 x1/2 = 1/16 

1/16 of the original activity will remain. Therefore 

1/16 x 1.0 mCi = 0.062 mCi.

How long will it take for 200 Ci of carbon 14 to 

decay to less than 1 Ci? (The half life is 5770 

years). 

A) 4000 years 

B) 40 years 

C) 44,000 years 

D) 80,000 years 

E) 88,000 years 


t1/2=5770 A1=activity at time time in question 

Ao=acitivty at time zero 

Time to reach =-ln(A1/Ao) x (t1/2/0.693) 

activity A1 =-ln(1/200) x (5770/0.693) 

=(-ln(.005) x (8326) 

= 44,114 years

Video display terminals have received much attention recently for 

their possible association with reproductive effects. The 

reproductive effects have been 

attributed to ionizing radiation and: 

A) Low Frequency pulsed magnetic fields 

B) Thermal stress 

C) Microwave emissions 

D) IR fields 

E) UV fields 


The main area of discussion has been the possible effects of low 

level pulsed magnetic fields. There have been several animal 

studies that have shown the waves to have potential teratgenic 

effects. The results have been difficult to replicate and some 

other exposures were not accounted for in the studies. This area 

will continue to be controversial.

If an individual incurred a dose equivalent of 5000 rem, how many 

Sieverts would it be? 

A) 5 

B) 50 

C) 500 

D) 5000 

E) 50,000 


One Sievert is equivalent to 100 rem, therefore 

5000 rem is equivalent to 50 Sv.

An activity of 3.7 E10 becquerel is equivalent 

to how many Ci? 

A) 1.0 

B) 0.1 

C) 0.01 

D) 0.001 

E) 0.0001 


One becquerel is equivalent to one disintegration per second. 

Since one Curie (Ci) has an activity of 3.7 E10 disintegrations 

per second any material that had this activity would equal one 

curie.

A "pig" is a: 

A) Container used to ship or store radioactive 

items 

B) A nuclear reactor 

C) Small ionization chamber to measure radiation D) Survey 

instrument to integrate dose 

E) Metal alloy used in detector walls 


The etymology of this word is Celtic and not related to an 

animal. It is normally a lead container used for shielding.

What is the formula for the relationship between 

energy of a particle and its mass? 

A) E = mc^2 

B) F = ma 

C) V = IR 

D) c = wavelength x frequency 

E) E = 1/2MV^2 


Einstein's formula relating mass and energy describes the 

fundamental relationship between the energy of a particle and its 

mass.

What is a "neutrino"? 

A) Massless particle 

B) Photon 

C) Neutron undergoing decay 

D) Beta antiparticle 

E) Positron antiparticle 


Neutrinos are products of beta decay which share 

energy with the beta particle. They must be 

defined to suit the physics conservation laws and are termed 

"massless particles that travel at the speed of light." 

Neutrinos are of no consequence in Health Physics because their 

probability of interaction is zero and thus give no radiation 

dose.

What is the mathematical relationship of the wavelength of a 

photon to its frequency? 

A) Direct 

B) Inverse 

C) Independent 

D) Equal 

E) Depends on the energy 


The wave equation: speed of light = frequency x 

wavelength. The speed of light is a constant, 

therefore the relationship is inverse, i.e. as the wavelength 

decreases the frequency will increase. Conversely, if the 

wavelength increases the frequency will decrease.

What is elastic scattering of a photon? 

A) Energy increase of scattered photon 

B) Energy decrease of scattered photon 

C) No energy change of scattered photon 

D) Total energy transfer to an electron 

E) Depends on incident energy 


Elastic scattering, also called Thomson scattering, or reflection 

in optics, is an example of a photon which changes direction but 

not energy.

What is inelastic scattering of a photon? 

A) No energy change in scattered photon 

B) Increase in energy of scattered photon 

C) Decrease in energy of scattered photon 

D) Total energy transfer to an electron 

E) Depends on incident energy 


When a photon scatters, it can lose energy to the medium or it 

can be scattered elastically with no loss of energy. Inelastic 

scattering is the decrease in energy of the scattered photon.

What is the "photoelectric effect" in regard to 

ionizing radiation? 

A) Total absorption of incident photon energy 

B) Partial absorption of incident photon energy C) Conversion of 

incident photon to mass 

D) Change in direction with no change in energy 

E) Change in direction with 2% energy absorption 


There are three processes to transfer energy from ionizing 

photons to matter: photoelectric, Compton, and pair production. 

In photoelectric interaction the incident photon energy is 

totally absorbed; in Compton the energy is partially absorbed 

with a scattered photon of less energy; in pair production the 

energy is converted into mass equivalents.

What happens to the incident photon in the 

Compton process? 

A) Total absorption of the incident energy 

B) Partial absorption of the photon energy 

C) Conversion of photon to mass 

D) Change in the direction with no energy change E) Change in 

direction with 2% absorption 


There are three absorption processes of incident 

photons in ionizing radiation: photoelectric effect, Compton 

effect, and pair production. In the first, the total energy of 

the photon is absorbed; in the second, the photon loses some 

energy to the medium and continues as a lesser energetic photon; 

and in the third the energy is converted into mass.

What happens to the incident photon in the pair production 

process? 

A) Total energy absorption 

B) Partial absorption 

C) Conversion of photon into mass 

D) Change in direction with no energy loss 

E) Change in direction with 2% absorption 


There are three absorption processes: photoelectric, Compton, 

and pair production. In PE the incident photon is totally 

absorbed; in Compton, the photon gives some energy to the medium 

and is scattered with less energy. In PP the photon energy, 

which must exceed 1.02 MeV, is converted into two electrons of 

opposite charge, each with 0.511 MeV of energy.

What does the "Z" represent in reference to 

an atom or an element or a nuclide? 

A) Amount of energy required to ionize the atom 

B) The proton number or effective proton number C) Atomic weight 

or atomic mass 

D) Probability of decay 

E) Neutron absorption cross section 


The atomic number, the number of protons, is referred to as the 

"Z" number. E.g., helium has a Z equal to 2. The photoelectric 

effect is highly Z Z dependent; the Compton effect is Z 

independent and pair production is slightly Z dependent.

Which effect predominates in the 10 keV - 100 keV range for 

photons? 

A) Photoelectric (PE) 

B) Compton 

C) Pair production (PP) 

D) Elastic scattering 

E) Inelastic scattering 


PE predominates in the above range. There can be some Compton 

effect, but due to the 1.02 MeV threshold in PP, there is no PP 

in this region. Elastic scattering can occur in any region, but 

does not predominate in this region.

Which effect predominates in the 100 keV - 10 MeV region for 

photons? 

A) Photoelectric effect (PE) B) Compton 

effect 





All effects occur in this region. PE and elastic scattering are 

minimal due to the high momentum of the photon. PP has a 

threshold at 1.02 MeV, but the effect does not dominate until 

very high energies. Compton predominates, and, since it is also 

Z independent, is the region of choice for radiation therapy and 

why lead aprons don't improve shielding.

What effect predominates in the greater than 

10 MeV ionizing region? 

A) Photoelectric Effect (PE) B) Compton 

effect 





Do not confuse 10 keV, the lower level for the ionizing region, 

with 10 MeV, the beginning of the energy range in which PP begins 

to dominate the absorption processes. The lower energy PE 

dominates until about 100 keV when Compton effect is about 50% of 

absorption process. Elastic scattering can occur but is of 

little importance in this range.

What is the energy equivalent of the electron? 

A) 1.6 x E-19 C 

B) Depends on sign of the charge 

C) 0.511 MeV 

D) 0.536 amu 



Electrons, positrons, positive betas, and betas all are 

equivalent to 0.511 MeV of energy, independent of charge. 

Einstein's formula, E = mc^2, is used to calculate the 

equivalents. A proton is equivalent to 938.2 MeV. One atomic 

mass unit (amu) is equivalent to 931.5 MeV.

What is the SI unit of activity? 

A) Ci 

B) Bq 

C) R 

D) Gy 

E) Sv 


Activity is the amount of disintegrations per unit time or a 

reciprocal time unit. There are two such units for radiation: 

curie and becquerel. The SI unit is the becquerel. 1 Bq=l dps.

A positron has the same mass as the: 

A) Proton 

B) Beta particle 

C) Charged nucleon 

D) Alpha particle 

E) Any of the above 


Positrons and beta particles differ in charge not mass. 

Positrons are positively charged electrons of nuclear origin.

The equivalent energy for the rest mass of a 

proton is about: 

A) 0.511 MeV 

B) 938 MeV 

C) 1 amu 

D) Z = 1 

E) 1837 keV 


The ratio of the mass of the proton to the electron is 1837, 

something you should know from chemistry. The ratio of the 

energies must be the same as per E = mc^2. From annihilation 

radiation processes, you know that the rest mass of the electron 

equals 0.5ll MeV. Multiply that number by 1837.

Which particle is considered to be radioactive 

by itself? 

A) Alpha 

B) Beta 

C) Neutron 

D) Positron 

E) Proton 


When removed from the nucleus of its atom, the 

neutron decays with a half-live of about 10.4 minutes into a beta 

particle and a proton.

Which of the following is isobaric decay? 

A) Alpha emission 

B) Beta emission 

C) Gamma emission 

D) Characteristic X-ray emission 

E) Fission 


In the beta decay processes, the Z of the decaying nucleus 

changes but not the mass. A beta particle or a positive beta is 

emitted with the corresponding neutrino. The mass of the 

original nucleus remains the same. This is isobaric decay.

Name the initial and final member of the uranium 

decay series. 

A) Th-232; Pb-208 

B) U-238; Pb-206 

C) U-235; Pb-207 

D) Np-237; Bi-209 

E) U-234; Rn-222 


The four series in A thru D have all occurred in nature. The 

neptunium series has decayed to the final product due to its 

relatively short half-life, and no longer occurs in nature. The 

uranium series is very important as it contains Rn-222 and 

Ra-226.

Name the initial and final nuclide in the thorium series: 

A) Th-232; Pb-208 

B) U-238; Pb-206 

C) U-235; Pb-207 

D) Np-237; Bi-209 E) Th-230; 

Pb-214 


The four series in A thru D have occurred in nature. However, 

the neptunium series has essentially decayed away, and no longer 

occurs in nature. The thorium series contains isotopes of radium 

and radon.

Name the initial and final members of the actinium series: 

A) Th-232; Pb-208 

B) U-238; Pb-206 

C) U-235; Pb-207 

D) Np-237; Bi-209 

E) Ac-227; Bi-209 


The four series in A thru D have occurred in nature, however, the 

neptunium series has essentially decayed away, and no longer 

occurs. The Uranium series contains Rn-222 and Ra-226. The 

Actinium series contains Rn-219 and Ra-223.

Name the initial and final member of the neptunium series. 

A) Th-232; Pb-208 

B) U-238; Pb-206 

C) U-235; Pb-207 

D) Np-237; Bi-209 

E) Np-239; Pb-207 


This series has essentially decayed away due to Neptunium's 

relative short half-life compared to that of the earth. It is 

not important for dose determination from natural sources. The 

most investigated series is that of U-238 since it contains 

Rn-222 and Ra-226. Its relative abundance is used to determine 

the age of earth.

Activation analysis occurs when: 

A) Radiation occurs after absorption of a neutron 

B) Nucleus is bombarded by a linear accelerator 

C) Betatron scans nucleus 

D) Leptons are produced 

E) Quarks are produced 


Neutron activation analysis occurs after a nucleus has absorbed a 

neutron and then radiates. The radiation is characteristic of 

that nuclide.

Plutonium: 

A) Occurs naturally 

B) Is very toxic 

C) Readily undergoes nuclear fusion 

D) Is easily produced in large quantities 



Plutonium is created in a nuclear reactor and is 

manmade. It is radioactive with a long half-life and is very 

toxic.

Technecium-99m is: 

A) A noble radioactive gas 

B) Artificially produced and does not occur 

naturally 

C) Used in medicine in Magnetic Imaging 

D) A positron emitter 

E) A beta minus emitter 


The element Tc does not occur in nature. The 

metastable state decays from Mo-99 with a half-life of 6 hr and 

is used extensively in the area of nuclear medicine. It has no 

known toxicity to man, has excellent chelating chemistry, and can 

be produced in a radiopharamacy in the hospital with little cost 

or radiation problems. As a metastable nuclide, it emits only 

gamma radiation of 140.5 keV. This is a desirable characteristic 

of a diagnostic radionuclide.

What is a use of a chelating agent? 

A) Change decay products to stable ones 

B) Chemically bind materials 

C) Change the activation energy of a 

radionuclide 

D) Measure radiation absorbed dose chemically 

E) To induce vomiting 


Chelating agents are used to bind radioactive materials. The 

chelating agent is used in medicine to give the patient a correct 

chemical form of radionuclide for diagnostics. It is also used 

to remove excess uptakes of nuclides from the body. An example of 

chelating agent for Pu and Am is DTPA. Sometimes chelating agents 

are used to clean surfaces by binding the contamination in a 

manner that makes cleanup easier or more effective. They may also 

be used in the decontamination of contaminated systems.

What is a "nuclide"? 

A) Element 

B) Nucleus with specific Z and A numbers 

C) Radioactive element 

D) Nucleus with specific mass number 

E) Radioactive isotope 


Nuclides specify the exact number of protons, neutrons, energy 

state of each, e.g., Tc-99m and Tc-99 ave different energy 

states. Also, more simply, a-226 and Ra-228 are different 

nuclides. A uclide does NOT have to be radioactive.

The periodic table lists: 

A) All elements 

B) All nuclides 

C) All radionuclides 

D) All naturally occurring elements 

E) All naturally occurring radionuclides 


The periodic table is a list of elements (atomic 

number) and electron structure. It does not list uclides or 

radionuclides. It also lists man-made elements such as 

technecium and the transuranics.

The process of combining two light nuclei into 

a third new nucleus is called: 

A) Fission 

B) Fusion 

C) Neutron activation 

D) Recombination 

E) Transmutation 


Fusion is the process in which two low Z nuclei combine and 

produce a third nuclei. For example, two hydrogen atoms can 

combine to form helium. This is fusion.

A radionuclide that is constantly being released 

by cosmogenic action is: 

A) C-14 

B) C-12 

C) K-40 

D) V-50 

E) He-4 


The two isotopes of carbon are present naturally, carbon-12 

(stable) and carbon-14 (radioactive). C-14 is produced by the 

(n,p) reaction on N-14. Another common cosmogenic nuclide is 

H-3, which is a spallation product from primary cosmic 

interaction with O and N. The neutrons which initiate C-14 

production are a portion of secondary cosmic radiation. 

Potassium-40 is a very long lived naturally occurring 

radionuclide and is present in soil and food.

100 pCi is equivalent to: 

A) 1 E-6 Ci 

B) 100 dpm 

C) 1 E 14 Bq 

D) 1 E-10 Ci 

E) 3.7 E-10 Ci 


In environmental counting, disintegrations per minute (dpm) are 

used more frequently than dps. Picocurie is 1 E-10 curie. 

Units are as follows: 

Curie 

millicurie 

microcurie 

nancurie 

picocurie

The target organ for consideration of biological 

damage to humans from laser exposure is the: 

A) Whole body 

B) Eye 

C) Skin 

D) Immune system 

E) Bone 


Target organ is the eye with a secondary organ of the skin.

All the natural radioactive decay series: 

A) Have very long half-lives 

B) Include Bismuth as a transmutant 

C) End in a stable isotope of lead 

D) Include primordial radionuclides 

E) Include fission fuels 


The neptunium series has decayed away with its relatively short 

half-life in comparison to that of the earth. It half-life is 

about 1 E 6 yr and terminates with Bi-209. The other three 

series, thorium, uranium, actinium, terminate in a stable isotope 

of lead.

If Kr-90 is released from the stack of nuclear 

plant, what radionuclide would be detected from 

its decay chain? 

A) Kr-90 

B) Sr-90 

C) Zr-90 

D) Sr-89 

E) Kr-89 


The chain: Kr-90 to Rb-90 to Sr-90 to Y-90 to Zr-90. This chain 

is environmentally important as strontium-90 has a 29.1 yr 

half-life and a plus two ionic charge. It appears in milk and 

grain products, is a bone seeker and can present a threat to 

children.

Strontium-90 is a very important radionuclide when discovered in 

the environment. It is a(n) _____ emitter. 

A) Alpha 

B) Beta 

C) Gamma 

D) Beta-gamma E) Positron 


The absorption of strontium into the bone matrix is as serious 

as the energy of the beta is high (Emax=546 keV), and the 

physical half-life is long (29.1 yr).

In a radioactive decay process in which a longer 

lived radionuclide decays into much shorter 

half-lived radionuclide, the process is called: 

A) Secular equilibrium 

B) Transient equilibrium 

C) No equilibrium 

D) Transmutation 

E) Depends on radionuclide 


In secular equilibrium the parent radionuclide has a much longer 

half-life than the daughter; in transient equilibrium the 

half-life of the daughter is of the same order of magnitude but 

shorter than that of the parent. If the parent half-life is 

shorter than that of the daughter, then there is no equilibrium.

In a radioactive decay process in which a long 

lived radionuclide decays into another radionuclide with a 

shorter but same order of magnitude half life, the process is 

called: 





E) Depends on radionuclide 


There is equilibrium whenever the parent radionuclide 

has a longer half-life than that of the 

daughter. For a difference larger than an order 

of magnitude, then the process is secular. If the half-life of 

the parent is shorter than that of the daughter, then there is no 

equilibrium.

In a radioactive decay process in which the parent radionuclide 

has a shorter half-life than that of the daughter, but same order 

of magnitude, the process is called: 





E) Depends on radionulcide 


The parent must have a longer half-life than that of the daughter 

for equilibrium to exist. In secular equilibrium the half-life is 

much larger for that of the parent; transient equilibrium, the 

same order of magnitidue.

The build-up factor in radiation shielding is 

caused by: 

A) Broad beam conditions 

B) Narrow beam conditions 

C) Particle emission 

D) Increments in shielding thickness 

E) Poor shielding materials 


The build-up factor, B, is equal to or greater than one. It is 

caused by incident photons scattered back to the detector by bad 

geometry, i.e., broad beam conditions. The B equals one under 

narrow beam conditions, i.e., good geometry.

A build-up factor equal to one in a radiation 

shielding equation occurs under: 

A) Broad beam conditions 

B) Narrow beam conditions 

C) Particle emission 

D) Increments in shielding thickness 

E) Use of poor shielding materials 


The build-up factor, B, in a radiation shielding 

equation is equal to or greater than one. For good geometry, B 

equals one; for poor geometry B is greater than one and is caused 

by the scattering of incident photons back into the detector 

area.

Semiconductor detectors are used primarily for 

their: 

A) High energy resolution 

B) Low cost 

C) Portability 

D) Atmospheric resilience 



The best current health physics detectors are made from 

semiconductor material. They operate with low voltage but may 

require cryostatic temperatures.

Radiation in the visible spectrum that results from the slowing 

down of charged particles in a medium is called _________ 

radiation. 

A) Bremsstrahlung 

B) Cerenkov 

C) Bragg-Gray 

D) Optical 

E) Infrared 


When a charged particle moves through a medium at a velocity 

greater than the phase velocity of light in that medium, the 

phenomenon observed is called Cerenkov radiation. 

Instrumentation for this effect is not used in health physics but 

the effect can be observed when a beta source is stored in water.

Full width half-maximum (FWHM) of the photopeak is a measurement 

of: 

A) Resolution 

B) Energy of the photon 

C) Energy of the charged particle 

D) Channel width 

E) Channel energy 


FWHM is a standard method for the measurement of 

resolution.

The energy distribution of alpha emission: 

A) Is monoenergetic 

B) Ranges from zero to a maximum 

C) Ranges from 1/3 maximum to a maximum 

D) Depends on radionuclide activity 

E) Depends on bound elements to the nuclide 


Alpha emission is monoenergetic and characteristic of the 

radionuclide; beta emission ranges from zero to a maximum 

characteristic of the radionuclide. The beta particle (or 

positive beta) shares the 

energy with the antineutrino (or neutrino).

Neutron activation is a process in which a "free" (unbound) 

neutron: 

A) Is produced in fission 

B) Is elastically scattered 

C) Is captured by a nucleus 

D) Decays 

E) Accelerates 


Many nuclei can absorb a neutron for a finite amount of time and 

produce an isotope of that nuclide. This nuclide is usually 

radioactive and decays with a characteristic radiation, which 

serves to identify the original nucleus. Arsenic in Napoleon's 

hair was identified by neutron activiation analysis.

Radium is considered to be a _______ seeker when 

internal to the body. 

A) Lung 

B) Bone 

C) Total body water 

D) Thyroid 

E) Liver 


All group II elements are considered bone seekers. They have a 

valence of 2+. Radium is especially important as the data from 

the radium dial workers has shown.

An ionization chamber has voltage great enough to cause: 

A) Ions before recombination; no secondary 

electrons 

B) Secondary electrons with a short range 

avalanche 

C) Secondary electrons with avalanche to whole 

anode 

D) Continuous discharge 

E) Recombination before current is produced 


Each answer above represents gas-filled detector responses in 

which the voltage begins at zero and is then increased. 

Recombination is first, then the ionization region; then the 

proportional region, the Geiger region, and then the continuous 

discharge region. Each gas-filled detector operates in one of 

these regions.

A proportional counter has enough voltage to cause: 

A) Ionization before recombination; no secondary 

electrons 

B) Secondary electrons with short range 

avalanche 

C) Secondary electrons with long range avalanche D) Continuous 

discharge 

E) Recombination prior to pulse 


Each answer above represents some part of the curve of for 

gas-filled detectors. First is recombination, then the 

ionization region, the proportional region, the Geiger region, 

and the continuous discharge region.

A Geiger counter has enough voltage to cause: 

A) Electrons before recombination; no secondary 

electrons 

B) Secondary electrons with a short range 

avalanche 

C) Secondary electrons with a long range 

avalanche 


E) Recombination prior to pulse 


Each answer above represents part of the six-region curve for 

gas-filled detectors. The first is recombination, then 

ionization; the proportional region; the Geiger region, and the 

continuous discharge region.

A Geiger counter should never have enough voltage to cause: 

A) Primary electrons 

B) Secondary electrons 

C) An avalanche of electrons 


E) Recombination 


To operate properly in the Geiger region of the 

six-region curve for gas-filled detectors, the voltage must be 

great enough to produce secondary electrons with an avalanche 

range extending the entire length of the anode but not exceed a 

voltage to cause breakdown of the potential field, i.e., 

continuous discharge.

Ionization chambers have gas amplification 

factors: 

A) Equal to 1 

B) Greater than 1 

C) Less than 1 

D) Dependent on the voltage 

E) Dependent on the volume 


A radiation detector used in the ionizing region 

has a gas amplification factor equal to one. Other instruments 

have gas amplification factors greater than one but not less than 

one.

Proportional counters have gas amplification factors that are: 

A) Equal to 1 






Ionization detectors in the ionizing region have 

gas amplification factors equal to one; other 

instruments have factors greater than one. Proportional counters 

in particular distinguish between alpha and beta radiation. Gas 

amplification factor greater than 1 means secondary electrons are 

produced, and that the detector operates in the pulse mode, not 

the current mode. The pulse occurs at a lower voltage for alpha 

than for beta, or, if counted at the same voltage, the alpha 

produces a larger pulse than the beta.

Geiger counters have gas amplification factors: 

A) Equal to 1 






Instruments that operate in the ionizing region have gas 

amplification factors equal to one; proportional counters and 

Geiger counter, greater than one. Proportional counters can 

distinguish between alpha and beta radiation whereas Geiger 

counters cannot. Detectors with gas amplification factors 

greater than 1 operate in a pulse, rather than current, mode.

The primary function of a radiation detecting 

instrument that operates in the proportional 

region is to measure: 

A) Alpha, beta, gamma 

B) Gamma only 

C) Beta distinguished from gamma 

D) Alpha distinguished from beta 

E) Alpha distinguished from gamma 


The reason that proportional counters are used in counting is 

that they can separate the alpha from the beta due to differences 

in pulse height. Since alphas have a higher specific ionization, 

they produce a larger pulse than beta at a given voltage.

The function of an "annular kinetic impactor head" is to trap: 

A) Airborne particles 

B) All surface contamination 

C) Surface contamination that would be permanent D) Liquid 

particles that are filtrable 

E) Particles with an AMAD less than 1 


For collecting alpha, beta, and gamma emitting contaminants, such 

as plutonium and fission products, it collects large airborne 

particles. What is particular to this collecting device is that 

it does not collect radon and thoron. The approximate efficiency 

is 95%.

What is the approximate efficiency for the radioiodines (I-125, 

I-131) on an activated charcoal filter at the appropriate flow 

rate for that instrument? 

A) 5% 

B) 25% 

C) 75% 

D) 95% 

E) 99% 


If the flow rate approaches 5 liters per minute, the efficiency 

can reach 98%.

What is the approximate efficiency for the detection of Xenon-133 

on activated charcoal? 

A) 1% 

B) 10% 

C) 50% 

D) 95% 

E) 99% 


Since it is a noble gas, the efficiency is usually less than 1%. 

Xenon concentration would have to be measured with a 

Marinelli-type grab sample or by direct gamma measurement in the 

atmosphere. This radioisotope of xenon is a by-product in the 

fission process in a nuclear reactor and is used in Nuclear 

Medicine as a lung scanning agent.

For what reason is a mica window used on a portable radiation 

detector? 

A) Low Z material to allow detection of beta 

radiation 

B) Maintains a partial vacuum well 

C) Light weight and inexpensive 

D) Machinable to correct geometry E) Deep dose 

tissue equivalence 


Mica is fragile and subject to fracture and requires a protective 

cap when the instrument is not in use. It is low Z that will 

allow low energy beta radiation through. It can be made shallow 

dose equivalent if used at a density thickness of 7 mg/cm2.

What scintillator material has a high efficiency for alpha 

measurement and is not especially affected by temperature, 

humidity, and barometric pressure ? 

A) Napthalene 

B) Mica 

C) ZnS 

D) NaI 

E) LiF 


ZnS has been used since the beginning of this 

century for alpha detection. A polycarbonate filter (about 0.8 

micron) is recommended to minimize contamination of the crystal 

if used for radon measurement. It is NaI that is used for gamma 

spectroscopy.

The function of a cascade impactor is to separate: 

A) Particles according to mass 

B) Radiation emissions (alpha, beta, gamma) 

C) Solid material from liquid 

D) Liquid material from gas 

E) Particlate radiation emission (alpha, beta) 


The cascade impactor separates particles according to their mass 

(diameter is also a determining factor). This is useful in 

characterizing the composition of airborne contaminants.

A pancake probe is used to: 

A) Filter out beta radiation from photons 

B) Be wedged between two others to detect betas C) Provide a 

large surface area 

D) Be applied outside of a faulty detector E) Perform 

fixed area radiation monitoring 


The pancake probe was designed for rapid checking of laboratory 

bench top and "frisking" of personnel. The large surface area 

provides a large sensitive volume to measure alpha and beta that 

could go undetected as background. It is required by NRC for 

some laboratories.

The "end window" on a Geiger-Mueller probe: 

A) Measures output from the aperture of x-ray 

machines 

B) Filters out alpha and beta radiation 

C) Is the low Z material for alpha and beta 

detection 

D) Discriminates alpha from beta radiation 

E) Discriminates alpha from gamma radiation 


The end window is the low Z material that allows penetration of 

alpha ,beta, and gamma. Some GM instruments are also equipped 

with a movable window to discriminate beta from gamma. The 

movable window, however, is not part of the detector wall as is 

the end window.

If 1 gram of radium equals 1 Ci and 1 mole 

of radon weighs 222 grams, what is the mass of 100 pCi of radon? 

A) 2.22 E-8 g 

B) 2.22 E-10 g 

C) 2.22 E-12 g 

D) 2.22 E-14 g 

E) 2.22 E-16 g 


100 pCi = 1 E-10 Ci 

(1 E-10 Ci) x (222g/Ci) = 222 E-8 g

The term "acute radiation syndrome" describes which of the 

following radiation exposure scenarios? 

A) Long term, moderate dose 

B) Long term, high dose 

C) Short term, moderate dose 

D) Short term, high dose 

E) Short term, low dose 


Radiation exposure to humans is broken into two 

groups: chronic and acute radiation exposure. 

Chronic exposure describes low dose, long term 

exposure, e.g. background radiation exposure. Acute exposure is 

of short duration and higher intensity.

Chronic radiation exposure is the result of: 

A) Low dose over a long time 

B) Moderate dose over a long time 

C) Low dose in a short time 

D) High dose in a long time 

E) Moderate dose in a short time 


Chronic radiation exposure usually involves low 

level exposures over a long period of time. Acute radiation 

syndrome is caused by exposure to high levels of radiation over a 

short period of time.

A fundamental law in radiobiology that has been in use for over a 

century is the Law of: 

A) Becquerel 

B) Bergonie & Tribondeau 

C) Bragg-Gray 

D) Curie 

E) Andersson-Braun 


This "law" states: radiosensitivity of a cell is directly 

proportional to metabolic activity and inversely proportional to 

degree of differentiation. It was Pierre Curie who approached 

Bergonie and Tribondeau to irradiate frog cells to do the initial 

radiobiological work as Madam Curie never accepted that radiation 

was damaging.

Localized (l cm2) high radiation burns sometimes 

occur in which of the following? 

A) Glove box workers 

B) Patients undergoing radiation therapy 

C) X-ray crystallographers 

D) Nuclear power reactor operators 

E) Diagnostic radiologists 


X-ray diffraction units can produce radiation 

burns (usually occurring when the interlocks are 

by-passed). Radiation monitors for these personnel are NOT worn 

nor required since only the index finger is the site of injury, 

and body monitoring cannot indicate dose. Radiation injury 

produced by such units can result in loss of the fingertip. 

X-ray diffraction units are used to examine the crystalline 

structure of materials. The materials are sometimes rotated by 

hand in the operating beam. This is an inappropriate practice in 

terms of radiation safety.

For transportation of radioactive materials, the 

Department of Transportation (DOT) classifies them as hazardous 

materials when their specific activity exceeds: 

A) 0.002 microcurie per gram 

B) 0.005 microcorie per gram 

C) 1000 dpm/100cm2 

D) 220 dpm/100cm2 

E) 2.2 dpm/cm2 


49 CFR 170-179 classifies the material as hazardous if the 

specific activity is greater than 0.002 uCi per gram.

Which radiation instrument below operates on the 

principle of discharging of a capacitor to estimate radiation 

dose? 

A) Pocket ionization chamber 

B) X-ray sensitive film 

C) Thermoluminescent dosimeter 

D) Proportonal counter 

E) Bubble detector 


The pocket chamber is a charged capacitor. As ionization occurs 

due to ionizing radiation exposure, the capacitor discharges and 

indicates the amount of exposure. Physical shock can likewise 

discharge the capacitor, yielding a false high dose.

Which radiation monitoring device uses a crystal 

with an added impurity to trap electrons during 

radiation exposure? 

A) Pocket dosimeter 

B) X-ray sensitive film 

C) Thermoluminescent dosimeter 

D) Plastic scintillator 

E) Long counter 


After the electrons are trapped, the TLD is subjected to a 

heating process. The trapped electrons emit optical photons 

(light) which is measured to determine exposure. Since heat is 

used and light is emitted, the name thermoluminescence is 

appropriate.

Both Cs-137 and I-131 are released as fission products by nuclear 

power plants. The biopathways for these two radionuclides can be 

traced via: 

A) Grain intake (cereals) 

B) Milk 

C) Leafy vegetables 

D) Potatoes 

E) Water 


Cs-137, I-131, Sr-90, and Sr-89 are picked up by cows from the 

grass and turn up in the milk which is consumed by humans. All 

of these nuclides are beta emitters. Cereals are a good indicator 

for Cs-137 and Sr-90, but not for I-131.

The pancake GM probe is designed for: 

A) Checking of surfaces 

B) High radiation dose measurement 

C) High radiation dose rate measurement 

D) Pulsed radiation fields 

E) Fixed area radiation monitoring 


The large surface area of a pancake detector is 

designed to make the GM sensitive enough to measure bench tops 

and personnel. This high sensitivity precludes its use in high 

radiation dose rate areas.

Non-bacterial radiopharmaceutical waste disposal: 

A) Requires separate marked waste containers 

B) Needs no separation from regular waste 

C) Requires a separate ventilated room 

D) Is not regulated by the NRC 

E) Has no special requirements 


Generally speaking, the medical pharmaceuticals have low toxicity 

and short half-lives. They are disposed into a marked recepticle 

during the day. They are removed to a locked storage area for 

decay to background and then disposed of with the regular trash. 

Typically, if the half-life is less than 100 days, they are held 

for ten half-lives prior to disposal as "clean" waste.

Human excreta containing medically administered 

radioactive materials: 

A) Must be collected and held 

B) Must be excreted into special containers 

C) Must be monitored 

D) Can be disposed of in ordinary sewage systems E) Is limited to 

1 curie per year 


Licensees for medical radiopharmaceuticals calculate sewage flow 

volume per year. Excreta radioactivity is exempt; non-excreta 

licensed material can be put into the sewage system at a rate of 

1 curie per year per institution. An additional 1 curie C-14 and 

5 curies H-3 is also allowed in the sewer per year under 10 CFR 

20.

Generally, to protect personnel against neutrons, use: 

A) High Z shielding (Z > 50) 

B) Low Z shielding (Z < 20) 

C) Middle Z shielding (20 < Z < 50) 

D) Albedo dosimetry 

E) Bubble detectors 


For neutrons, a hydrogenated material such as paraffin or lucite 

is used. The hydrogen atoms are good neutron moderators. Care 

should be taken to shield the resulting gammas from hydrogen 

activation with a high Z material.

What is a "phantom" in reference to radiation exposure studies? 

A) Calculation of ideal point in radiation 

formula 

B) Type of radiation detection system 

C) Non-portable survey or monitoring unit 

D) Material to simulate tissue 

E) Unanticipated double beta decays 


Phantoms are tissue-equivalent material, i.e., 

materials that simulate absorption of radiation in the same 

manner as tissue.

The "working level" (WL) used in the USA and 

Canada as a unit of radon decay is: 

A) 1 liter water with emission of 1.3 E5 MeV 

alpha 

B) 1 liter air with emission of 1.3 E5 MeV alpha C) Amount 

received averaged over 40 hours 

D) Volume of air averaged over 40 hours 

E) 1 E-7 pCi/L 


A working level is any combination of radon daughters in one 

liter of air that will result in the ultimate emission of 1.3 E5 

MeV of alpha energy. 1 working level is equivalent to 100 pCi/L 

air of Rn-222 in equilibrium with its daughters. 1 working 

level is also equivalent to 3 times the DAC of Rn-222 from 10 

CFR 20, Appendix B.

The Department of Transportation (DOT) label White I allows a 

dose equivalent on the surface of the package: 

A) Less than 5 uSv per hr 

B) Between 5 uSv per hr and 100 uSv per hr 

C) Between 100 uSv per hr and 500 uSv per hr 

D) Greater than 500 uSv per hr 

E) No greater than background 


49 CFR 173 describes the labels. Radioactive White I is full 

white with one red vertical stripe. There can be no measureable 

radiation at 1 meter, and must be less than 5 uSv (0.5 mrem) per 

hour on the package surface.

The Department of Transportation (DOT) label White I allows what 

radiation dose rate at 1 meter? 

A) None above background 

B) Less than 5 uSv per hr 


D) Between 100 uSv per hr and 500 uSv per hr 

E) Greater than 500 uSv per hr 


49 CFR 173 describes the labels. Radioactive White I is all 

white with one red vertical stripe. The surface radiation rate 

allowed must be less than 5 uSv per hr with no measureable 

radiation at 1 m.

The Department of Transportation (DOT) label Yellow II allows 

what radiation dose rate at 1 meter? 


B) Up to 5 uSv per hr 

C) Up to 10 uSv per hr 


E) Between 100 uSv per hr and 500 uSv per hr 


49 CFR 173 describes the labels. Radioactive Yellow II has two 

vertical red stripes with upper half yellow and bottom white. 

Surface radiation rate allowed lies between 5 and 500 uSv per hr. 

Dose rate at 1 meter cannot exceed 10 uSv (1 mrem) per hr.

The Department of Transportation (DOT) label Yellow II allows 

what radiation dose rate on the surface of the package? 





E) Up to 2000 uSv per hr 


49 CFR 173 describes the labels. Radioactive Package II has two 

vertical red stripes. The upper half is yellow; bottom white. 

Surface radiation dose rate allowed is up to 500 uSv (50 mrem) 

per hr. Dose rate at 1 meter may be up to 10 uSv (1 mrem) per 

hr.

The Department of Transportation (DOT) label Yellow III allows 

what surface radiation dose rate, when the package is shipped 

non-exclusive use? 




D) Between 500 uSv per hr and 2000 uSv per hr E) Betwen 500 

uSv per hr and 5000 uSv per hr 


49 CFR 173 describes the labels. Radioactive Yellow III has 

three vertical red stripes. The surface radiation rate allowed 

is 500-2000 uSv/hr (50-200 mrem/hr). The upper limit at 1 meter, 

if shipped non-exclusive use, is 500 uSv/hr (50 mrem/hr).

Medical use of byproduct material falls under which part of 10 

CFR? 

A) Part 19 

B) Part 20 

C) Part 30 

D) Part 35 

E) Part 50 


Four parts of the Code that are important to know: 

Part 19--Notices, Instructions, Reports to Workers 

Part 20--Standards for Protection Against Radiation 

Part 30--Licensing of By-Product Material 

Part 35--Medical Use of Byproduct Material

KERMA is a unit of radiation measurement expressed in: 

A) Joule per kilogram 

B) Joule per coulomb 

C) Coulomb per kilogram 

D) Disintegrations per kilogram 

E) Disintegrations per liter 


The KERMA (kinetic energy released in material) and absorbed dose 

differ in magnitude only if the energy transferred by the charged 

ionizing particle to the medium is not totally absorbed by the 

material. The KERMA is less than the absorbed dose, for 

instance, when radiative loss of energy (bremsstrahlung) is 

substantial. In this case, energy escapes via photons, with low 

probability of subsequent interaction in the material. KERMA is 

equal to absorbed dose when all energy loss is by collision of 

the charged particle in the material.

Transportation of all types of packages including those which 

have radioactive contents fall under which federal agency? 

A) EPA 

B) NBS 

C) DOT 

D) OSHA 

E) NRC 


It is useful to know the abbreviations for the agencies above and 

something about scope of authority and enforcement. 

EPA= Environmental Protection Agency 

NBS= National Bureau of Standards 

DOT= Department of Transportation 

OSHA= Occupational Safety and Health Administration 

NRC= Nuclear Regulatory Commission

How does the NRC regulate x-ray machines? 

A) Any medical x-ray machine 

B) Any x-ray machine except medical x-ray 

machines 

C) All x-ray machines 

D) NRC does not regulate x-ray machines 

E) Only through agreement states 


NRC regulates reactor-produced radionuclides and 

not x-ray machines. The state generally regulates them according 

to their own regulations, regardless of whether the state is an 

NRC Agreement State. 

OSHA has authority to enforce its standards to 

protect hospital workers.

The NRC regulates radionuclides produced in a 

linear accelerator by which criterion? 

A) Greater than a minimum activity 

B) Greater than a minimum specific activity 

C) Each radionuclide falls into its own category D) NRC does not 

regulate these radionuclides 

E) Through agreement states only 


Radioactive materials (RAM) produced by a reactor are called 

by-product materials. These are regulated by the NRC. 

Accelerator produced radionuclides are not regulated by the NRC. 

Many states however do regulate them, regardless of NRC agreement 

state status.

The SI unit for radiation absorbed dose is the: 

A) Gray 

B) rad 

C) Sievert 

D) rem 

E) Becquerel 


The gray (Gy) is defined as 1 Joule per kilogram. It is the SI 

counterpart of the rad, which is 100 ergs per gram.

The SI unit for dose equivalent in man is the: 

A) Gray 

B) Rad 

C) Sievert 

D) Rem 

E) Becquerel 


The Sievert is defined as a quality factor times the dose in 

Gray. The rem is the "special unit" counterpart and is equal to 

0.01 Gy.

The SI unit of activity is the: 

A) Hertz 

B) Becquerel 

C) Curie 

D) Gray 

E) Sievert 


The becquerel is the SI unit for activity and is 

equal to one disintegration per second.

The underlying principle for measurement of 

radiation absorbed dose is the ____________ 

principle. 

A) Bragg-Gray 

B) Bergonie and Tribondeau 

C) Becquerel and Curie 

D) Einstein 

E) Coulomb 


The Bragg-Gray principle relates absorbed dose in a medium 

(usually the detector wall material) to a measurement of a known 

amount of ionization in a small volume of a gas-(usually 

air)filled cavity.

The underlying principle for radioresponse of a 

mammalian tissue is called the Law of _________. 

A) Bragg and Gray 

B) Bergonie and Tribondeau 

C) Becquerel and Curie 

D) Curie and Joliet 

E) Bragg-Gray 


The Law of Bergonie and Tribondeau states that 

radioresponsiveness is directly proportional to mitotic activity 

and inversely proportional to degree of differentiation of the 

cell.

Which of the below quality factors (QF) apply to 

diagnostic x-rays? 

A) 0 

B) 1 

C) 5 

D) 10 

E) 20 


X-rays and gamma rays have quality factors of 1.

As a charged particle loses energy in a medium and begins to slow 

down and then stop, where along the path from entry to stop is 

most of the energy deposited? 

A) Entry (0 depth) 

B) Electron equilibrium 

C) End of path 

D) Equally along path 

E) Beginning 1/3 of path 


Charged particles lose most of energy at end of 

path, particularly the monoenergetic ones. The 

Bragg Peak is an example of the large dose deposited at the end. 

Betas lose most of the energy at 2/3 maximum range.

In the fission process in a nuclear reactor, many radionuclides 

are produced; yet some radionuclides are considered environmental 

indicators of contamination, e.g. Sr-90 and I-131. Why? 

A) They are toxic 

B) The exposure pathways are significant 

C) They are volatile 

D) They are short-lived 

E) They are long-lived 


Iodine-131 has an 8 day half-life and strontium-90, a 29.1 yr 

half-life. Their presence is easily detected in milk. This is 

largely due to the broad area a cow traverses to obtain her food.

What is the mathematical relationship between the decay constant 

and the physical half-life? 

A) Inverse square 

B) Linear 

C) Direct 

D) Inverse 

E) Equal 


Since the physical half-life is equal to 0.693/decay constant, 

the physical half life is inversely proportional to the decay 

constant. Therefore, materials with a short half life have large 

decay constants and vice versa.

What is the SI unit for the decay constant? 

A) Second 

B) 1/second 

C) Bq 

D) Hz 

E) ln 2 


The SI decay constant unit is 1/second or second^-1. Bq 

(becquerel) is the SI unit for activity; Hz is a unit for 

frequency.

The "lapse rate" is the: 

A) Temperature gradient of the atmosphere 

B) Rate of decay 

C) Initial activity minus decayed activity 

D) Inhalation rate of noble gases 

E) Period between initial decay and equilibrium 


Atmospheric conditions are an important consideration for the 

evaluation of downwind discharges from stacks. There are many 

models for estimation of dispersion of radionuclides, which 

include the lapse rate as a variable.

An atmospheric inversion is one in which the 

lapse rate is: 

A) Positive 

B) Negative 

C) Continuous 

D) Zero 

E) Lognormal 


If the lapse rate is positive, then the air 

temperature increases with increasing height. This condition is 

a very stable condition and undesired since the stack effluents 

tend to sink. This is a consideration in stack studies involving 

release of radionuclides.

The best data to use to estimate the hazard of 

radiation to genetic damage is: 

A) Rat data 

B) Rat and mouse data 

C) Human data 

D) Mathematical modeling 

E) Beagle data 


Human data is the best evidence for any study of effects on 

humans, radiation or otherwise.

When calculating for structural shielding, the 

occupancy factor can have a value of: 

A) 1 

B) 1 or 1/4 

C) 1 or 1/16 

D) 1, 1/4, or 1/16 

E) 1, 3/4, 1/4, or 1/16 


Full occupancy, T = 1, consists of control space, work rooms, 

living quarters, restrooms used by occupational workers, waiting 

rooms, and corridors large enough to hold personnel. Partial 

occupancy, T = 1/4, is used for utility rooms, rest rooms of 

non-occupational workers, narrow corridors. For Occasional 

occupancy: stairways, closets are T=1/16 

Reference: NCRP Report No. 49.

What is a disadvantage of a long sample counting time for 

optimization of counting statistics? 

A) Resolution poorer 

B) Instrument saturates 

C) Background may change 

D) Sample may decay 

E) There is no disadvantage 


Background can vary in certain instances, for instance,if 

radioactive materials are being transported nearby while an 

instrument is counting or if atmospheric conditions cause 

background radiation fluctuation.

A sample of radioactive material is reported to 

contain 2000 picocuries of activity. Express this value as 

disintegrations per minute. 

A) 370 dpm 

B) 900 dpm 

C) 2200 dpm 

D) 4440 dpm 

E) 7770 dpm 


1 curie= 3.7 E10 disintegrations per second. 

There are 60 seconds in one minute. 1 picocurie is equal to 1 

E-12 curie. Therefore, 

(3.7 E10) x (1 E-12) x (60) x (2000) = 4440

Given a reading of 100 mr/hr (gamma) at 10 feet, 

what would be the reading at 2 feet assuming a 

point source geometry? 

A) 500 mr/hr 

B) 1000 mr/hr 

C) 2200 mr/hr 

D) 2500 mr/hr 

E) 5000 mr/hr 


Use inverse square law. r2=(100)x(10/2)^2 . 

The radiation level drops off as one over the 

square of the distance. answer= 2500 mr/hr

What would be a good approximation of the 

quality factor (QF) of the neutrino? 

A) 0 

B) 1 

C) 5 

D) 10 

E) 20 


Since neutrinos have essentially zero probability of interaction 

they cannot cause ionization along their path through the tissue. 

Hence the quality factor will be zero.

Which of the following is not a naturally occurring radionuclide? 

A) carbon-14 

B) potassium-40 

C) radium-226 

D) xenon-133 

E) vanadium-50 


Carbon-14, potassium-40, radium-226, and vanadium-50 are 

naturally occurring radionuclides. Xenon-133 is manmade, as a 

fission product.

Notices to radiation workers and instructions to 

workers fall under which part of 10 CFR? 

A) Part 19 

B) Part 20 

C) Part 30 

D) Part 35 

E) Part 50 


Four parts to the Code that should be familiar 

are: 

Part 19--Notices, Instructions, Reports to Workers 

Part 20--Standards for Protection Against Radiation 

Part 30--Licensing of By-Product Materials 

Part 35--Medical Use of Byproduct Material

The occupational derived air concentration (DAC) is calculated 

based on the average airborne concentration that a person would 

receive in what period of time? 

A) 40 hr week 

B) 168 hr week 

C) 2000 hr year 

D) 2080 hr year 

E) Depends on the radionuclide 


Derived air concentration is the average concentration over a 

2000 hr period. It is calculated by dividing the ALI by the 

product of the reference man breathing rate (1.2 cubic meters per 

hour) and 2000 hrs.

If a point source of radiation had 1000 units of gamma radiation 

at 1 ft, what would the radiation level be at 10 ft? 

A) 10000 units 

B) 1000 units 

C) 100 units 

D) 10 units 

E) 1 unit 


Since radiation obeys the inverse square law the 

radiation would be 1/10^2 of that at 1 foot. Hence, 1/100 x 1000 

= 10 units.

What does an "alpha" emission consist of? 

A) an electron 

B) an electromagnetic wave 

C) 2 neutrons and 2 protons 

D) 1 neutron and 1 proton 

E) 1 triton and 1 neutron 


An "alpha" emission consists of 2 neutrons and 2 protons (a 

helium nucleus). This type of ionizing radiation is easily 

shielded as an external source, but it is considered an internal 

radiation hazard as it can cause heavy damage in tissue. 

External shielding can consist of paper.

A radium decay scheme looks like the following: 

226 XXX 

Ra -> alpha particle + Rn 

88 XX 

What does "XXX" represent? 

A) 226 

B) 225 

C) 224 

D) 222 

E) 220 


As an alpha particle is a helium nucleus it contains 2 neutrons 

and 2 protons for an atomic mass of 4. Losing 4 atomic mass 

units converts Radium 226 to Radon 222.

A radium decay scheme is represented by the following: 

226 XXX 

Ra -> alpha particle + Rn 

88 XX 

What does "XX" represent? 

A) 88 

B) 87 

C) 86 

D) 85 

E) 84 


An alpha particle contains 2 neutrons and 2 protons thereby the 

release of one alpha particle decreases the element's atomic 

number by 2 as only protons are counted for atomic number.

What is the chemical symbol for Radon? 

A) Ra 

B) Rd 

C) Ro 

D) Rn 

E) R 


Radon is represented on the Periodic Table by the symbol "Rn". 

"Ra" denotes Radium.

In the beta particle decay of strontium the following occurs: 

90 XX 

Sr -> Beta electron + 

38 ZZ 

Y 

What is the "XX" value for yttrium (Y)? 

A) 91 

B) 90 

C) 88 

D) 87 

E) 86 


The "XX" refers to the mass number for Yttrium. As beta decay 

causes no change in the mass number it remains at 90 for Yttrium.

In the beta decay of Strontium the following occurs: 

90 XX 

Sr -> beta electron + Y 

38 ZZ 

What is the value "ZZ" for Yttrium (Y)? 

A) 39 

B) 38 

C) 42 

D) 37 

E) 36 


Beta decay causes an increase of +1 in the atomic number as a 

negative mass is leaving atom. A +1 increase in the atomic 

number increases the atom's ranking on the periodic table to the 

next higher element. Therefore "ZZ" is 39.

What is a Roentgen? 

A) The amount of X or gamma radiation that 

produces ionization resulting in 1 

electrostatic unit of charge in 1 cc of dry 

air at STP 

B) Absorption of 100 ergs of energy from any 

radiation in 1 gm of any material 

C) The "biological" dose to living tissue 

D) 98 ergs per gram of any absorber 

E) 3.34 E-10 Coulombs/kilogram 


A Roentgen is a measurement of exposure whose definition is given 

in "A". The measurement of absorbed dose (rad) definition is 

given in "B". A rem is the biological dose. One Roentgen will 

deposit 87 ergs per gram of air, 98 ergs per gram of tissue, and 

will create 3.34 E-10 Amperes per cc of dry air at STP.

The target organ for radium is the: 

A) Bone 

B) GI tract 

C) Lung 

D) Thyroid 

E) Spleen 


The uptake of radium is incorporated into the bone possibly 

leading to bone cancers. Other target organs for radionuclides 

include: 

Isotope 

Tritium 

Strontium 

Iodine 

Plutonium 

Target Organ 

Total body 

Bone 

Thyroid 

Bone

Why are the low atomic number materials such as aluminum and 

organic plastics used to shield against Beta? 

A) Cheaper to use 

B) Eliminate Bremmsstrahlung 

C) Higher atomic number materials are not 

effective 

D) Lighter than lead 

E) They can be transparent 


Beta particles can generate Bremmsstrahlung (braking radiation) 

x-rays when they are slowed too quickly by hitting materials of 

high atomic numbers. Therefore, aluminum and plastics with 

atomic numbers < 14 are utilized for shielding.

Which of the following government agencies regulates the 

classification and control measures incorporated into laser 

products? 

A) OSHA 

B) EPA 

C) NRC 

D) FDA 

E) ACGIH 


The Food and Drug Administration regulates the classification and 

control measures incorporated into laser products, high mercury 

lamps, and sunlamps.

The TLV for exposure to radiation from a microwave oven is: 

A) 10 W/cm2 

B) 10 mW/cm2 

C) 100 W/cm2 

D) 100 mW/cm2 

E) 1000 mW/cm2 


The TLV for microwave radiation from a microwave oven is 10 

mW/cm^2. This is based on a frequency of 2450 MHz.

The most abudant radionuclide in the earth's crust on the average 

is: 

A) Thorium 

B) Uranium 

C) Plutonium 

D) Carbon 

E) Radium 


In the U.S., on the average, one square mile dug to one foot 

would yield: 

6 tons Th-232 

3 tons U-nat 

1 ton K-40

Which of the following series is an artifically produced decay 

series? 

A) Thorium 

B) Neptunium 

C) Actinium 

D) Uranium 

E) Radium 


The three natural decay series are Thorium, Actinium, and 

Uranium. They each begin with Th-232, U-235, and U-238, 

respectively. They are also denoted as 4n, 4n+3, and 4n+2, 

respectively. The Neptunium decay series begins with Np-237 and 

is denoted as 4n+1. Once a naturally occurring series due to 

natural sustained fission reactions, the Np series has decayed 

away and no longer exists in nature.

Which two nuclides are prodcued by cosmogenic action? 

A) Ar-39 and Sr-90 

B) H-3 and C-14 

C) C-14 and Sr-90 

D) H-3 and Ar-40 

E) N-1 and Ar-40 


H-3 is a spallation product fron primary cosmic interactions of 

heavy nuclei with the atmosphere. C-14 is created by secondary 

cosmic interactions (in this case, neutrons) in the N-14 (n,p) 

C-14 reaction.

In an absorbing medium, one gray (100 rads) would produce: 

A) 1 E 2 ergs/gm 

B) 1 E 4 ergs/gm 

C) 1 E 6 ergs/gm 

D) 1 E 10 ergs/gm 

E) 1 E 12 ergs/gm 


Since 1 rad produces 100 ergs per gram of absorber, 1 Gray (100 

rads) produces 10,000 ergs per gram of absorber, or 1 E 4. 1 

Gray is also equal to 1 Joule per kilogram of absorber.

If an isotope has a DAC of 1 E-8 microcuries/ml and it will be 

released through a stack with a flow rate of 1 E 6 liter/hr, how 

many microcuries of the isotope can be released at a constant 

rate in one day without exceeding the DAC? 

A) 240 

B) 120 

C) 24 

D) 1.0 

E) 0.4 


1 E-8 uCi/ml x (1 E6 L/hr x 24 hr x 1 E3 ml/L)= 

240 uCi

A one liter Marinelli air sample is counted on a system which 

indicates 30,000 counts per minute. If the system has a counting 

efficiency of 17%, the activity of the sample is: 

A) 1.76 E+3 Bq/ml 

B) 2.90 E+0 Bq/ml 

C) 7.95 E+1 Bq/ml 

D) 1.06 E+10 Bq/ml 

E) 1.06 E+7 Bq/ml 


[30,000 c/(1 L x 1 E3 mL/L)x(.17)] x (1 Bq/60 dpm) = 

2.9 Bq/mL

95-Am-241 has ______ protons and _______ neutrons. 

A) 95, 146 

B) 95, 241 

C) 95, 336 

D) 146, 95 

E) 241, 95 


In the term Z-X-A: 

Z is the number of protons 

X is the chemical symbol for the element 

A is the number of protons and neutrons (nucleons) 

A - Z = number of neutrons

If an atom is assembled from its constituent parts (electrons, 

protons, and neutrons), the mass of the assembled atom is less 

than the sum of the mass of the parts, largely because: 

A) free electrons are less massive than bound 

electrons 

B) coulombic repulsion among protons tends to 

decrease the effective mass of the protons 

C) the requirements of quantized angular 

momentum demand a reduction in mass 

associated with an increase in total system 

angular momentum 

D) of the transformation of constituent mass to 

binding energy 

E) the gravitons required to complete the 

assembly uses up mass from the consitutent 

parts 


Since E = mc2, energy can be converted to mass, and vice versa. 

The difference in mass between the component parts and the 

assembled atom is termed "mass defect".

Isotopes are defined as: 

A) different radionuclides decaying by the same 

decay mode 

B) forms of the same element containing 

different numbers of neutrons 

C) forms of the same element containing 

different numbers of electrons 

D) topes that have a temperature of 32F 

E) radioactive species containing the same 

number of neturons PLUS electrons 


Isotopes have the same number of protons and a different number 

of neutrons. Isotones have the same number of neutrons and a 

different number of protons. Isobars have the same "A" number. 

Isomers have a parent nuclide in a metastable state.

You have 400 millicuries of a radionuclide on June 15th. On June 

20th, you have 350 millicuries of the material. How much of the 

material will be present on July 15th of the same year? 

A) .02 curies 

B) .08 curies 

C) .15 curies 

D) .18 curies 

E) .45 curies 


Use A = Ao e^-(lambda x t) 

First establish the decay constant (lambda): 

350 = 400 e^-(lambda x t) 

lambda = .0267/day 

Then plug in new time: 

A = 400 e^-(.0267/day x 30 days) 

A = 179.5 mCi

If a radionuclide undergoes eight half-lives, what percentage of 

the original activity remains? 

A) 0.15% 

B) 0.4% 

C) 0.78% 

D) 1.5% 

E) 12.5% 


Use A = Ao (1/2)^n 

A = 100% (1/2)^8 

A = 0.39%

The difference between x-rays and gamma photons of the same 

energy is their: 

A) frequency 

B) wave-length 

C) origins 

D) properties 

E) mass 


Gammas originate from the nucleus, while x-rays originate from an 

electron shell, or in the case of bremsstrahlung, at some point 

outside of the nucleus.

In an elastic scattering interaction between a neutron and an 

atomic nucleus, which one of the following statements is true? 

A) a gamma photon will always be produced 

B) a proton or a neutron will be emitted from 

the nucleus 

C) interaction with a heavy nucleus will result 

in proton recoil 

D) characteristic X radiation is always produced 

E) kinetic energy transferred to the nucleus is 

independent of the mass of the nucleus 


In the case of elastic scattering with a light nucleus such as 

hydrogen, a recoil proton is produced. In elastic scattering 

with a heavier nucleus, the neutron simply scatters off. 

Elastic scattering is often represented by the "marble and 

bowling ball" analogy.

A 7 mg/cm2 mylar window is used on a radiation detector. What is 

the minimum beta particle energy required to reach the detector 

fill gas? 

A) 7 keV 

B) 70 keV 

C) 700 keV 

D) 900 keV 

E) 1 MeV 


7 mg/cm2 is significant because it is the density thickness used 

for shallow dose equivalent. Thus, it requires a 70 keV beta 

particle to penetrate the dead layer of skin.

Secondary radiation following photoelectric interaction can 

include: 

1) scattered photons 

2) photons of shorter wavelengths 

3) characteristic x-rays 

4) auger electrons 

5) neutrons 

A) 1,2,3,4,5 

B) 1,2,3,4 

C) 1,3.5 

D) 2,3,4 

E) 3,4 


There are no scattered photons, since the photon is completely 

absorbed. The characteristic x-rays created would have longer, 

not shorter wavelengths. The production of neutrons would 

require a photoneutron interaction, which is not described by 

photoelectric interaction.

Effects of acute radiation exposure on the central nervous system 

can be observed at doses of: 

A) 1000 rads 

B) 500 rads 

C) 250 rads 

D) 100 rads 

E) 25 rads 


CNS syndrome, where an electrolytic imbalance from excessive 

ionization causes nervous system dysfunction, does not occur 

until about 1000 rads of total body irradiation.

Genetic effects produced by radiation in males are dependent on: 

1) State of germ cell development 

2) LET of the radiation 

3) Interval between the exposure and conception 

A) 1,2,3 

B) 1,2 

C) 1,3 

D) 1 

E) None of the answers 


Germ cells in the male are spermatozoa. Bergonie and Tribondeau 

show that cell maturity is indeed a factor in radiosensitivity. 

LET is certainly a factor since a higher LET causes a higher 

probability of interaction in a fixed volume of spermatozoa. The 

interval between exposure and conception is important since time 

could be allowed for repair of marginally damaged cells or death 

of very damaged cells.

What is the "threshold" of radiation dose effects? 

A) the dose of radiation that will kill any 

organism 

B) the dose of radiation that will kill 50% of 

those exposed 

C) the dose of radiation below which there are 

no effects whatsoever on the body 

D) the dose of radiation that will begin to 

alter cell structure 

E) the dose of radiation at which the damage 

effect is just balanced out by recovery 


The "threshold", as used here, only applies to non-stochastic 

effects of radiation. The current dose effect theories (linear 

and linear-quadratic) assume that some biological effect occurs, 

no matter how small the dose.

The three naturally-occuring radioactive decay chains are: 

A) Thorium, Neptunium, Uranium 

B) Polonium, Plutonium, Neptunium 

C) Hydrogen, Oxygen, Carbon 

D) Thorium, Actinium, Uranium 

E) Neptunium, Actinium, Polonium 


The Thorium, Actinium, and Uranium series begin with the nuclides 

Th-232, U-235, and U-238, respectively. The fourth decay series 

is Neptunium, which no longer occurs naturally and begins at 

Np-237.

Which of the following radionuclides is NOT a naturally occurring 

radionuclide? 

A) K-40 

B) Cs-137 

C) Ra-226 

D) U-235 

E) Ra-228 


Cs-137 is a fission product. It may appear directly as a fission 

fragment, or occur from the beta-minus decay of Xe-137. K-40 is 

a primordial radionuclide. The remaining nuclides are members of 

naturally occurring decay series.

The dose equivalent to the U.S. population from all man-made 

sources of radiation is given by the NCRP as: 

A) 60 mrem/year 

B) 300 rem/year 

C) 1.5 rem/year 

D) 5 rem/year 

E) 12 rem/year 


NCRP Report 93 (1987) shows the average annual radiation exposure 

to the population of the United States to be 360 millirem. 300 

mrem is due to natural sources (200 from radon/thoron and 

daughters). The remaining 60 mrem is from man-made sources (53 

from medical sources).

Most of the dose received by man from man-made sources of 

radiation is due to: 

A) the operation of nuclear power reactors 

B) industrial applications of radiation and 


C) medical applications of radiation and 


D) fallout from nuclear weapons testing 

E) Ra-226 


NCRP Report No.93 (1987) shows the average annual radiation 

exposure to the population of the United States to be 360 mrem. 

300 mrem is due to natural sources. Of the remaining man-made 

contribution (60 mrem), 53 is due to medical uses of radiation 

and radionuclides.

One roentgen is equal to: 

A) 1 coulomb/kg air 

B) 33.7 eV/kg air 

C) 2.58 E-4 coulomb/kg air 

D) 100 ergs/kg air 

E) 87 ergs/kg air 


The Roentgen is the measure of ionization of air by photons less 

than 3 MeV. Thus, we are looking for an answer with units of 

electrostatic charge in a volume of air. This eliminates answers 

D and E. Answer B is a distractor that uses the value 33.7, 

which when expressed as eV is the "W" value of air. The value of 

2.58 E-4 coulomb/kilogram should be remembered. Other values of 

the Roentgen: 

1R = 1 esu/cc air 

1R = 87 ergs/gm air 

1R = 98 ergs/gm tissue 

The air measurements refer to dry air at STP, which is 0 degrees 

centigrade, 760 mm Hg.

For an isotope having an allowed concentration of 1 E-5 

microcuries/cc, what is the minimum discharge time to not exceed 

the concentration when 1.5 curies of activity are discharged into 

a stream having a flow rate of 140,000 gallons/hour? (1 gallon = 

3785.6 cc). 

A) 1.5 hours 

B) 10.7 hours 

C) 140 hours 

D) 283 hours 

E) 1072 horus 


In setting up this equation, look for what units must appear in 

the solution. Since we are looking for time: 

(uCi/cc/hr)/(uCi/cc) = hrs 

Then: 

[(1.5 Ci x 1E6 uCi/Ci)/(140,000 gal x 3785.6 cc/gal/hr)] 

_______________________________________________ 

1 E-5 uCi/cc 

Solving the above equation gives you: 

2.83 E-3 uCi/cc/hr 

= __________________ 

1.0 E-5 uCi/cc 

= 283 hrs

The energy absorbed by 1 gram of air exposed to 1 Roentgen of 

gamma rays is equivalent to: 

A) 100 ergs 

B) 100 rads 

C) 32.5 eV 

D) 87 ergs 

E) dependent upon the radiation energy 


The Roentgen is a measurement of the ionization of air by 

photons. Air, as used when quantifying the Roentgen, is dry air 

at STP (0 degrees C, 760 mm Hg). Representations of the Roentgen 

which are useful to remember: 

1R = 1 esu/cc air 

1R = 2.58 E-4 coulombs/kilogram air 

1R = 87 ergs/gm air 

1R = 98 ergs/gm tissue

All of the following statements about atomic structure are true 

EXCEPT: 

A) the nucleus carries a positive charge 

B) protons and neutrons are collectively known 

as "nucleons" 

C) the diameter of the nucleus is relatively 

small compared to the diameter of the atom 

D) electrons, protons, and neutrons are all of 

about equal mass 

E) electons carry a negative charge 


Electrons are about 1/1837 the mass of a proton. The rest mass 

energy equivalence of an electron is .511 MeV, for 1 atomic mass 

unit (amu) it is 931.5 MeV. Protons have a mass energy 

equivalence of 938.256 MeV, neutrons 939.550 MeV.

The radius of the nucleus of an atom as compared to the atom as a 

whole is: 

A) some 10,000 times greater 

B) some 1,000 times greater 

C) some 10,000 times smaller 

D) some 1,000 times smaller 

E) some 100 times smaller 


Contrary to many pictorial representations of the atom, the 

nucleus is relatively small. If the nucleus were the size of an 

orange, the diameter of the atom would be on the order of 1000 

yards.

Isotopes are: 


decay mode 

B) forms of the same element containing 


C) forms of the same element containing 

different numbers of protons 

D) radioactive species containing the same 

number of neutrons plus electrons 

E) daughter products of radioisotopes in 

equilibrium 




different number of protons. Isobars have the same number of 

nucleons.

What are isotones? 

A) nuclides with the same mass number 

B) nuclides with the same number of neutrons 

C) nuclides with the same atomic number 

D) same nuclides at different excited states 

E) activated isotopes 


Isotones have the same number of neutrons, but a different number 

of protons. Isotopes have the same number of protons, but a 

different number of neutrons. Isobars have the same number of 

nucleons.

Which of the following has the highest specific activity? 

A) one gram of U-238 

B) one gram of Cs-137 

C) one gram of Co-60 

D) one gram of P-32 

E) one gram of Ra-226 


Specific acivity is activity per unit mass. Since the mass is 

constant for each choice (one gram), it must be determined which 

has the highest decay rate. Since the decay rate has an inverse 

relationship to the half-life, the nuclide with the shortest 

half-life will have the highest decay rate and, therefore, the 

highest activity. The half-lives are as follows: 

U-238 4.47 E9 y 

Cs-137 30.17 y 

Co-60 5.27 y 

P-32 14.82 d 

Ra-226 1.6 E3 y

Emission of a negatively charged beta particle results from the 

transformation of: 

A) a neutron into a proton 

B) a proton into a neutron 

C) a neutrino into a neutron 

D) a positron into a proton 

E) an electron into a proton 


If one thinks of the neutron as a particle having one positive 

charge and one negative charge, it is easy to visualize a proton 

being created (positively charged) when the negatively charged 

beta particle is emitted. Such a process occurs during beta 

minus decay and when a free neutron decays.

Following electron capture, the following processes may occur: 

A) 1,3 

B) 1,3,4 

C) 2,3 

D) 2,3,4 

E) 3,4 

1) Z increases by 1 

2) Z decreases by 1 

3) Characteristic x-rays are emitted 

4) Auger electron emission 


We know that selections 1 and 2 cannot both be correct, however 

this does not help since 1 and 2 do not both appear in the same 

answer. Good try. During electron capture, a high 

proton-to-neutron ratio causes the nucleus to capture a 

negatively-charged electron from the K-shell, transforming a 

proton to a neutron. Z has decreased by 1. Then, a higher 

energy level electron fills the vacancy in the K-shell. The 

difference in electron energies is emitted as a characteristic 

x-ray, which if it ionizes the "host" atom, will produce Auger 

electrons. Additional characteristic x-rays are produced as 

other higher energy level electrons fall to the lowest available 

energy sites in a cascade fashion.

Which of the following radionuclides requries the least mass to 

comprise one curie? 

A) U-238 

B) Rb-88 

C) Co-60 

D) Mn-54 

E) Cs-137 


Since the curie is measured by the decay rate, the nuclide with 

the highest decay rate will require the least mass to make a 

curie. Since decay rate is inversely related to half-life, the 

shortest half-life will yield the highest decay rate. The 

half-lives are as follows: 

U-238 4.47 E9 y 

Rb-88 17.7 m 

Co-60 5.27 y 

Mn-54 312 d 

Cs-137 30.17 y

A technician surveys a shielded pure beta-emitting source and 

obtains a measurement of 0.2 R/hr. If all beta particles are 

shielded, the reading is caused by: 

A) Compton scattering in the shield material 

B) pair production in the shield material 

C) photoelectric effect in the shield material 

D) bremsstrahlung 

E) Cerenkov photons 


Since all betas are shielded, it is apparent that the reading is 

due to photons. This could be confirmed by the fact that the 

measurement is given in units of Roentgen, which only applies to 

photons. Since the source is a "pure beta-emitter", the photons 

are being produced by bremsstrahlung.

The dose to tissue from 6 MeV neutrons is delivered primarily by: 

A) high speed electrons 

B) lower energy neutrons 

C) recoil protons 

D) alpha particles 

E) activation products 


Fast neutrons interact by scattering. Since tissue is comprised 

largely of hydrogen, elastic scattering with hydrogen is 

producing high-LET recoil protons. Since the interaction of the 

protons is much more probable than for the neutrons, or resulting 

capture gammas, these deliver most of the dose.

In the interaction of thermal neutrons with tissue, the major 

dose is from: 

A) elastic scattering by hydrogen atoms 

B) the N-14(n,p)C-14 reaction 

C) inelastic scattering by hydrogen atoms 

D) the H-1(n,gamma)H-2 reaction 

E) the H-2(n,gamma)H-3 reaction 


Thermal neutrons interact by absorption (also called capture). 

Dose is produced by the interactions described in both B and D. 

Even though the gamma has a much lower LET than the proton, the 

dose is greater in D due to the great amount of hydrogen present 

in the body.

The average energy required to produce an ion pair in air by x or 

gamma radiation is: 

A) 16 eV 

B) 32 eV 

C) 32.5 eV 

D) 33.7 eV 

E) 35 eV 


Also called the "W" value of air. All gases can be assigned a W 

value. It is of particular importance in radiation measurements 

using gas-filled detectors.

Which of the following organ systems is the MOST radiosensitive? 

A) central nervous system 

B) bone marrow 

C) gastrointestinal system 

D) muscle system 

E) skeletal system 


Use the Law of Bergonie and Tribondeau, as well as the heirarchy 

of effects from the Acute Radiation Syndrome to solve this 

question.

The following are considered as risks of chronic low-level 

radiation exposure: 

A) 1 

B) 2 

C) 3 

D) 1,3 

E) 2,3,4 

1) sterility 

2) leukemia 

3) cataracts 

4) skin erythema 


The risk of chronic, low-level exposure, such as occupational 

exposures, is for stochastic effects only. The only stochastic 

effect shown is leukemia.

Which of the following radionuclides is a bone seeker? 

A) Ca-45 

B) I-125 

C) I-131 

D) Kr-85 

E) Co-60 


The metabolism of radionuclides in the body is dependent upon 

chemical form. Since stable calcium goes to the bone, so to does 

radioactive calcium.

"Below a certain radiation dose, no effects whatsovever occur in 

the human body." This statement supports which dose/effect 

theory? 

A) Threshold 

B) Linear Non-Threshold 

C) Non-Linear Non-Threshold 

D) Linear Quadratic 

E) The "Hormesis" Effect 


The threshold theory is not commonly subscribed to for 

radiation-induced stochastic effects.

Why are the dose equivalent limits for occupationally exposed 

persons so much higher than those set for members of the general 

public? 

A) radiation worker are paid enough to 

compensate for the risk 

B) radiation workers have continous monitoring 

of their exposure and the work environment is 

continously monitored 

C) radioactive materials licensees only hire 

workers with a limited knowledge of 

radiological principles 

D) the number of radiation workers is very low 

compared to the population so the total risk 

is very small 

E) radiation workers develop a higher tolerance 

for the effects of ionizing radiation than 

that of the general public 


In Cost-Benefit analysis in radiation protection, the benefit of 

an implemented process, technology, etc. must outweigh the 

detriment. For a benefit to an entire population, the total 

radiation detriment is small, since radiation workers comprise 

such a small percentage of the total population.

If a linear relationship between somatic effects of radiation and 

absorbed dose is assumed, the number of additional cancers deaths 

to be expected per million persons per rad is: 

A) >100 

B) 20 

C) 50 

D) 10 

E) 2 


BEIR V (1990) estimates an additional 800 cancer mortalities in a 

population of 100,000 exposed to 10 rad. This can be 

extrapolated to 800 per 1 million per 1 rad, if effect to dose is 

assumed to be linear.

Why is a child more radiosensitive than an adult? 

A) an adult has better health 

B) a child's cells are weaker 

C) a child's cells are multiplying more rapidly 

D) a child's cells have less ability to repair 

damage 

E) a child's cells are smaller 


This is a simple application of the Law of Bergonie and 

Tribondeau.

The Systeme Internationale units Gray and Sievert represent the 

same respective quantities: 

A) rad and curie 

B) rem and curie 

C) curie and rad 

D) rad and rem 

E) rem and rad 


Special Unit 

SI Unit 

100 rad 1 Gray 

100 rem 1 Sievert 

1 dps(2.7 E-11 Ci) 1 Becquerel

If a large group of people receive an acute deep dose of 450 

rads, what fraction of the people would you expect to be alive in 

2 months if they receive no medical treatment? 

A)

Of the following cell types, which is LEAST radiosensitive? 

A) lymphocytes 

B) endothelial cells 

C) epithelial cells 

D) nerve cells 

E) erythrocytes 


Using the Law of Bergonie and Tribondeau and the heirarchy of 

effects from the Acute Radiation Syndrome, it becomes easy to 

select cells in their order of radiosensitivity. CNS syndrome 

occurs at the highest dose during acute exposure. Also, nerve 

cells are non-dividing, highly specialized, and very mature.

What is the main factor determining the amount of energy that can 

be transferred to the electron during Compton scattering? 

A) the resultant characteristic x-ray 

B) differences in energy between "K" and "L" 

shell sites 

C) the scattering angle 

D) the energy of the scattered gamma photon 

E) nuclear binding energy 


The scattering angle of the incident photon is inversely 

proportional to the energy of the scattered photon, and therefore 

directly proportional to the energy transferred to the electron. 

In other words, the greater the scattering angle, the greater the 

energy transferred to the electron, and the less the energy of 

the scattered photon.

According to NCRP Report No. 93, the average annual radiation 

dose to persons in the United States from natural and man-made 

sources is: 

A) 100 mrem 

B) 260 mrem 

C) 300 mrem 

D) 360 mrem 

E) 500 mrem 


The 1987 report increased previous estimates by about 200 

millirem, largely due to the contribution of radon/thoron 

daughters.

The range of a 2 MeV alpha particle in air is about: 

A) 0.2 cm 

B) 1.0 cm 

C) 6.5 cm 

D) 7.5 cm 

E) 9.5 cm 


There are classical calculations available to estimate alpha 

particle range based on energy. A simple thumb rule is .5 cm/MeV 

below 2.5 MeV, and .75 cm/MeV above 2.5 MeV.

For a radionuclide with a decay constant of 0.693 per minute, the 

fraction of atoms that undergoes decay in three minutes is: 

A) 0.250 

B) 0.875 

C) 0.693 

D) 0.069 

E) 0.125 


Use A = Ao e^-(lambda x t) 

But remember, we are looking for the fraction which has decayed, 

NOT the fraction remaining. The fraction which has decayed will 

be represented by (Ao - A)/Ao. 

So, let Ao = 1, 

and: 

A = 1 e^-(.693/min x 3 min) 

= .125 

then: 

(1 - .125)/1 = .875

An isotope is one of two or more atoms with: 

A) the same number of protons and a different 

number of electrons 

B) the same number of protons and a different 

number of neutrons 

C) the same number of neutrons and a different 

number of protons 

D) the same atomic weight 

E) the same mass number 




different number of protons. Isobars have the same number of 

nucleons.

The NCRP has reported which of the following to be the largest 

contributor to radiation exposure of the general population? 

A) radiation from nuclear power plants 

B) medical x-rays 

C) cosmic and ultraviolet radiation 

D) radon and thoron daughters 

E) consumer products 


Radon/thoron daughters comprise 200 mrem of the 360 mrem annual 

average radiation exposure from all sources in the United States. 

Data is from NCRP Report No.93, 1987.

The symbols Pa, Ga, Sn, Ni represent which respective elements? 

A) protactinium, gallium, tin, nickel 

B) protactinium, gadolinium, tin, nickel 

C) palladium, gallium, tin, nickel 

D) palladium, gadolinium, tin, nickel 

E) praseodymium, gallium, tin, nickel 


It is helpful to memorize chemical symbols of the elements either 

from the Periodic Table or the Chart of the Nuclides.

The primary mechanism for charged particles to lose energy in a 

medium are: 

A) nuclear interactions involving ejection of 

multiple particles from the target nucleus 

B) bremsstrahlung effects arising in the 

electronic structure of the medium 

C) ionization and excitation affecting the 

electronic structure of the medium 

D) gravitation interactions 

E) pair production interactions 


Charged particles interact by ionization and excitation, and in 

the case of beta particles, bremsstrahlung. Effects on electrons 

can alter the structure of atoms in the absorbing medium.

If the maximum beta particle energy for a radionuclide is 7.0 

MeV, the average beta particle energy is approximately: 

A) 2.33 MeV 

B) 0.223 MeV 

C) 1.43 MeV 

D) 0.256 MeV 

E) 700 keV 


The average beta particle energy is calculated as 1/3 Emax, where 

Emax is the maximum beta particle (or "endpoint") energy.

The mass defect is equal to: 

A) the difference in binding energies between 

parent and daughter nuclides 

B) the difference between the mass of the 

nucleus as whole and the sum of the component 

nucleus masses 

C) the rest mass of particulate radiations 

emitted by the daughter nuclide 

D) the sum of the binding energies of the parent 

and daughter nuclides 

E) the rest mass energy equivalence of the 

daughter nuclide 


This difference in mass is equivalent to the "binding energy" of 

the nucleus. An illustration of E = mc^2.

The major source of radiation exposure averaged over the United 

States population is from: 

A) natural background radiation 

B) diagnostic medical applications 

C) therapeutic medical applications 

D) fallout from nuclear weapons 

E) releases from the fuel cycle necessary to 

support the civilian nuclear power program 


According to NCRP Report No.93 (1987), of the 360 mrem annual 

average exposure to the population of the U.S., 300 mrem is due 

to natural radiation. The components of natural radiation 

include cosmic and terrestrial sources. The largest contributor 

is radon/thoron daughters, at about 200 mrem.

The desired quantity of Technetium-99m (t1/2 = 6 hrs) for a 

medical procedure is 100 millicuries. If the shipment takes one 

day to reach the facility, what quantity of Technetium-99m should 

be shipped? 

A) 200 millicuries 

B) 800 millicuries 

C) 1.6 curies 

D) 1.8 curies 

E) 2.2 curies 


Using A = Ao e^-(lambda x t), solve for Ao 

Ao = A/[e^-(lambda x t)] 

= 100 mCi/[e^-(.693/6 hr x 24 hr)] 

= 1600 mCi 

= 1.6 Ci

In the energy range from 0.1 to 5 MeV in either air or water, the 

most predominant photon interaction is: 

A) pair production 

B) Compton scattering 

C) photoelectric effect 

D) Rayleigh scattering 

E) Thomson scattering 


Photoelectric effect predominates below 200 keV, Compton 

scattering between 200 keV and 5 MeV, and Pair production above 5 

MeV.

A researcher orders 10 mCi of I-131, which has an 8-day 

half-life. If it takes 16 days for the shipment to reach its 

destination, then the minimum quantity that must be shipped is: 

A) 40 mCi 

B) 20 mCi 

C) 60 mCi 

D) 80 mCi 

E) 100 mCi 


Use A = Ao e^-(lambda x t) and solve for Ao. 

Ao = A/[e^-(lambda x t)] 

= 10 mCi/[e^-(.693/8 d x 16 d)] 

= 40 mCi

The Roentgen is a measure of: 

A) absorbed exposure to gamma rays 

B) absorbed exposure to gamma and x-rays 

C) exposure to gamma rays only 

D) exposure of air to gamma and x-rays 

E) absorbed dose in air 


The Roentgen is a measure of exposure, i.e. the ionization of air 

by photons. The Roentgen is only defined for photons (x or 

gamma) in air below 3 MeV. 

The Roentgen may be quantified as 2.58 E-4 Coulombs/kilogram air 

or 1 esu/cc air.

Isobars are: 


mode 

B) radioactive species containing the same 

number of nucleons 

C) forms of the same chemical element containing 


D) elements with the same number of neutrons 

E) gradients in radiation levels 


Isobars have the same number of nucleons (same "A" number). 

Isotopes have the same number of protons, but a different number 

of neutrons. Isotones have the same number of neutrons, but a 

different number of protons.

The antineutrino is associated with what process? 

A) beta minus decay 

B) beta plus decay 

C) electron capture decay 

D) alpha decay 

E) neutron capture 


The "Q" value in a beta minus decay is shared by the beta 

particle and the antineutrino, and unless the nuclide is a "pure 

beta emitter", also a gamma photon. In positron decay (beta 

plus) or electron capture decay, the neutrino shares this energy.

Background radiation contributing to external dose in a wooden 

house versus a concrete building is probably: 

A) greater because of the greater shielding 

provided by the concrete building 

B) less because of the natural radioactivity in 

the concrete 

C) equal to the external radiation in the 

concrete building 

D) less because of the external radiation from 

radon and thoron emanations from the concrete 

E) greater because of the natural Potassium-40 

in the wood 


The closest distractor in this question is D, however, radon and 

thoron emanations pose an internal, rather than external, hazard.

The three types of blood cells in the human body are: 

A) erythrocytes, leukocytes, platelets 

B) erythrocytes, red blood cells, platelets 

C) white blood cells, leukocytes, platelets 

D) leukocytes, granulocytes, platelets 

E) red blood cells, white blood cells, granulocytes 


The blood is composed of red blood cells, white blood cells, 

platelets, and plasma (water). Red blood cells are clinically 

named erythrocytes and white blood cells are leukocytes. 

Granulocytes are a subgroup of white blood cells.

Charged particles interact with matter by which of the following? 

A) photoelectric effect and Compton scattering 

B) inelastic collision 

C) elastic scattering 

D) excitation and ionization 

E) Bremsstrhlung and pair production 


Charged particles lose energy by collision and radiative 

processes. The two collision processes are excitation and 

ionization. Radiative loss occurs for beta particles and 

secondary electrons by bremsstrahlung.

The range of an alpha particle in tissue is approximately 50 to 

100: 

A) centimeters 

B) millimeters 

C) microns 

D) angstroms 

E) barns 


Since the alpha particle energy is not given, we assume an energy 

range of 4-8 MeV, which is typical for alpha decay in natural and 

man-made radionuclides. Alphas in this energy range will travel 

50-100 um in a material of unit density such as tissue.

Which of the following is NOT an isobaric transformation? 

A) beta minus decay 

B) beta plus decay 

C) alpha decay 

D) electron capture 

E) isomeric transition 


We know that isobars have the same number of nucleons (same "A" 

number). The only type of decay shown which does not yield a 

daughter of the same "A" is alpha decay, where "A" decreases by 

4.

After four half-lives, the original activity of a radionuclide 

will be reduced by a factor of: 

A) 4 

B) 8 

C) 16 

D) 32 

E) 64 


Use A = Ao (1/2)^n and solve for Ao/A. 

So: 

Ao/A = 1/(1/2)^n 

= 1/(1/2)^4 

= 16

If Gallium has two naturally occurring isotopes, Gallium-68.926 

with a 60.11% abundance and Gallium-70.925 with a 39.89% 

abundance, what is the atomic weight of natural Gallium? 

A) 33.53 

B) 34.86 

C) 34.96 

D) 69.72 

E) 69.93 


The atomic weight of natural Gallium will be equal to the sum of 

the ratios of each naturally occurring isotope of Gallium. So: 

A = (68.926 x .6011) + (70.925 x .3989) 

= 69.72

Workers are exposed to a Cs-137 concentration of 5 E-4 

microcuries/cc for 2 hours. Calculate their approximate 

committed effective dose equivalent as a result of inhalation. 

GIVEN: Mass of lung: 

5809 grams 

Reference Man 

Breathing Rate: 

1E 7 cc/8 hr 

137-Cs DAC: 

6E-8 uCi/cc 

A) 2.1 E3 mrem 

B) 8.3 E3 mrem 

C) 4.2 E4 mrem 

D) 8.3 E4 mrem 

E) 4.2 E5 mrem 


Assuming the DAC is based on the sALI, a simple DAC-hour 

calculation will be sufficient to calculate the CEDE. When the 

DAC is based on the sALI, one DAC-hour is equal to 2.5 millirem. 

When the DAC is based on the nALI, one DAC-hour is equal to 25 

mrem to the target tissue. So: 

CEDE = [(concentration/DAC) x hrs] x 2.5 mrem/DAC-hr 

= [(5 E-4/6 E-8) x 2] x 2.5 

= 4.16 E4 mrem

Assuming a normal cancer fatility rate of 20%, what would be the 

total probability of developing a fatal cancer for a group of 

occupationally exposed workers with a 3 in 1,000 probability of 

contracting a radiation induced fatal cancer: 

A) 3 in 1,000 

B) 20 in 1,000 

C) 230 in 1,000 

D) 203 in 1,000 

E) 200 in 1,000 


total = normal probability + occupational probability 

= (200 in 1000) + (3 in 1000) 

= 203 in 1000

Based on the 1990 BEIR V Report, the weighted average risk of 

death from cancer follwing an acute dose equivalent of 0.1 Sv of 

low-LET radiation to all body organs is estimated to be: 

A) 1 E-4 

B) 8 E-3 

C) 2 E-3 

D) 8 E-4 

E) 1 E-2 


BEIR V estimates 800 additional cancer deaths in a population of 

100,000 exposed to 10 rad. Since the radiation weighting factor 

is 1 for low-LET radiation, we can assume that 10 rad is equal to 

10 rem. 0.1 Sv equals 10 rem. Therefore, the risk is 

800/100,000 or 8 E-3.

All of the following are applicable to the lung cancer observed 

in uranium miners EXCEPT: 

A) miners who also smoke are observed to have a 

much higher incidence of lung cancer than 

non-smokers 

B) cancer is observed primarily in the bronchial 

epithelium region 

C) cancer is probably associated with the 

radiation dose from "hot particles" 

D) cancer is believed to be the result of the 

dose delivered by radiation emitted from 

radon daughter products deposited in the 

respiratory tract 

E) cancer in observed primarily in workers who 

have a number of years in the industry 


Hot particles are not encountered in the mining of natural 

uranium. All other distractors are valid data.

Based on the laws of Bergoinie and Tribondeau, rate the following 

cells from most to least sensitive. 

1. intestinal crypt cells 

2. nerve cells 

3. mature spermatocytes 

4. lymphocytes 

5. erythrocytes 

A) 4,5,1,3,2 

B) 4,1,3,5,2 

C) 1,4,3,2,5 

D) 1,4,5,3,2 

E) 3,4,1,5,2 


Also use the heirarchy of effects from the Acute Radiation 

Syndrome to rank cells in their order of radiosensitivity. 

Knowing that white blood cells are the most radiosensitive 

immediately narrows the choice to only A or B. B is the better 

choice, since erythrocytes (no nucleus, specialized) are less 

radiosensitive than intestinal crypt cells (unspecialized, 

rapidly dividing).

Ionizing radiation has been directly associated with cataract 

formation. Select the statement which is INCORRECT. 

A) the cataractogenic dose response is 

considered a threshold effect 

B) fast neutrons are more effective at producing 

cataracts than other forms of radiation 

C) the cataract effect is dependent on age at 

time of irradation 

D) occupational exposure to x-rays accounts for 

approximately 1% of the cataracts observed in 

x-ray technicians 

E) radiogenic cataracts are distinct in that 

they originate on the anterior epithelium of 

the lens 


The lens is rarely exposed in occupational medical x-ray 

applications. Even when it is, it is far less than the annual 

limit of 15 rem (.15 Sv) on the average. Since the limit is set 

to allow much less of an incidence of cataracts than 1%, this 

statement is incorrect. All other distractor data are valid.

Which one of the following lists the skin response to acute 

radiation exposure in correct chronological order? 

A) dry desquamation, moist desquamation, 

erythema, recovery 

B) moist desquamation, dry desquamation, 

erythema, recovery 

C) dry desquamation, moist desquamation, 

recovery, erythema 

D) erythema, dry desquamation, moist 

desquamation, recovery 

E) erythema, moist desquamation, dry 

desquamation, recovery 


The order may also be termed: reddening, peeling, blistering, 

recovery.

The ICRP 26 risk factor used for stochastic effects is: 

A) 0.01 per Sievert 

B) 0.001 per Sievert 

C) 0.0001 per Sievert 

D) 0.002 per Sievert 

E) 0.05 per Sievert 


This risk factor is based upon the annual mortality rate in safe 

industries, which is 1 in 10,000 or 1 E-4. A risk of 1 E-4 per 

rem would be the same as a risk of 1 E-2 per 100 rem. Since 100 

rem equals 1 Sievert, the risk per Sievert is 1 E-2, or 0.01.

Genetic mutations are one possible result of exposure to ionizing 

radiation. Select the correct response regarding genetic 

effects. 

A) within a population, a mutation is usually 

manifested in the first generation of 

offspring 

B) since many mutations are recessive, a large 

dose to a small population will cause more 

genetic damage than a small dose to a larger 

population 

C) hereditary defects are relatively rare, 

occuring

Which of the following radionuclides is not included in the 

definition of Working Level? 

A) Rn-222 

B) Po-218 

C) Pb-214 

D) Bi-214 

E) Po-214 


The working level is defined as that amount of radon daughters 

which produces 1.3 E5 MeV alpha energy per liter of air. It does 

not include the contribution of radon itself. All other 

distractors are Rn-222 daughters.

The roentgen is equal to: 

A) 1.0 coulomb/kg 

B) 1.00 E-3 coulomb/kg 

C) 5.28 E-3 coulomb/kg 

D) 2.58 E-4 coulomb/kg 

E) 5.28 E-4 coulomb/kg 


It is helpful to memorize the following values for the Roentgen: 

1R = 2.58 E-4 coulomb/kg air 

= 1 esu/cc air 

= 87 ergs/gm any absorber 

= 98 ergs/gm tissue

Radioactive atoms that have a neutron to proton ratio that is 

great will decay by: 

A) beta plus decay 

B) beta minus decay 

C) electron capture decay 

D) alpha decay 

E) isometric transition 


If the neutron to proton ratio is high, the atom will transform a 

neutron to a proton to reach stability. It will accomplish this 

by ejecting a negatively charged beta particle.

Cancer induced by radon daughters in underground mines is found 

primarily in the: 

A) upper trachea and bronchial tree 

B) upper pulmonary parenchyma 

C) lower trachea and bronchial tree 

D) nasal passage 

E) lower pulmonary parenchyma 


NCRP #78 "Attributed to inhalation of the airborne, short-lived 

daughters Po-218, Pb-214, Bi-214 and Po-214"

The absorbed alpha dose to cells in the _________ in the upper 

airways of the tracheobronchial tree is the significant dose for 

cancer induction in miners. 

A) larynex epithelium 

B) bronchial epithelium 

C) pulmonary epitheial 

D) trachea epithelium 

E) bronchial epidermis 


Bronchial epithelium-NCRP #78

Unlike many man made materials, where radon release is very low, 

most soils have the ability to release more than ______ of the 

radon formed. 

A) 10% 

B) 20% 

C) 30% 

D) 40% 

E) 60% 


NCRP #78 "The fraction of radon released from a solid material 

depends on its porisity and whether radiation is on or near the 

surface of the material. It is currently believed that the source 

of most of the radon is the soil beneath a structure"

10CFR20 requires Very High Radiation Areas to be posted at 500 

Rad/hr at 1 meter. All other radiation postings in 10CFR20 are 

based on mrem/hr dose rates. The Very High Radiation Area posting 

requirement is in Rad/hr because: 

A) The type of radiation is unknown so mrem 

cannot be reported. 

B) Radiation detection instruments are 

unrealiable at high dose rates. 

C) Neutron detection instruments read out in 

mrem/hr eliminating the need to calculate 

dose. 

D) The type of radiation is unknown so mrem must 

be calculated for the type of instrument 

used. 

E) Quality factors do not apply to dose rates 

this high. 


"The values of Q have been selected on the basis of relevent 

values of reletive biological effectiveness but they also take 

into account the fact that the dose-equivalent limits are based 

on extrapolations from higher absorbed doses at which deleterious 

effects in man can be directly assessed. These values of Q are 

therefore not necessarily representative of values of RBE for 

other observed effects such as non-stochastic effects in man at 

high absorbed doses. It is particularly important that dose 

equivalent should not be used to assess the likely early 

consequences of severe accidental exposure." 

ICRP 26 page 5

Deleterious effects caused by radiation exposure to gonads may 

take the form of: 

A) fertility problems and stochastic effects 

B) tumor reduction and somatic effects 

C) fertility problems and hereditary effects 

D) tumor induction and tetrogenic effects 

E) hereditary and tetrogenic effects 


ICRP 26 page 9. Radiation exposure may cause effects of three 

different types: tumour induction, fertility problems and 

hereditary effects

ICRP 26, Recommendations of the ICRP, identify radiosensitive 

cells in the bone as: 

A) haematopoitic and trabecular cells in the 

bone 

B) endosteal and epitheal cells on the bone 

surface 

C) epithelial and epedermial cells on the bone 

surface 

D) epedermial and lymphocyte cells in the bone 

E) platlets and lymphocyte cells in bone marrow 


ICRP 26 The Commision recommends that where possible, dose 

equivalent in the bone should apply to the edosteal cells and 

cells on bone surfaces, and should be calculated as an average 

over tissue up to a distance of 10 micrometer from bone surface.

Cigarette smokers who smoke 1.5 packs a day receive approximately 

8 Rem/yr to the lungs due to: 

A) Rn-222 and Po-210 

B) Ra-226 and Po-210 

C) Bi-214 and Ra-226 

D) Po-218 and Pb-214 

E) Pb-210 and Po-210 


NCRP 56 page 29

During criticality accidents, exposure to neutrons will induce 

radioactivity such as activation of a normal body element top 

form the gamma emitting isotope: 

A) Na-24 

B) P-32 

C) Cs-137 

D) Co-60 

E) I-131 


NCRP 65 page 29

Sr-85 is used in the treatment of bone cancer because it is: 

A) a beta emitter that eliminates carcinomas in 

the bone marrow 

B) a gamma emitter that is absorbed in the bone 

C) a beta emitter that is taken up by the bone 

D) a gamma emitter that concentrates in sites of 

active osteogresis 

E) a beta emitter that remains in healthy bone 

for a period of years 


Sr 89 is a beta emitter which localizes in the bone. major 

feature is that it is calcium analog, meaning very little uptake 

in the bone marrow. Marrow is sparred high doses from absence of 

gamma emissions. Sr89 is taken up by tumors and cancer sites and 

rapidly washes out of healthy bone. 

Health Physics Journal Vol 69 No 5 (Paul Early Edward Lasada 

1995)

Natural Uranium consists of three primary isotopes whose natural 

abundances are: 99.2739, 0.7204, and 0.0057. Those isotopes from 

high abundance to low are: 

A) U-238, U-235, and U-230 

B) U-239, U-238, and U-235 

C) U-238, U-235, and U-232 

D) U-238, U-235, and U-234 

E) U-239, U-238, and U-232 


The decay products of these uranium isotopes consist of long 

decay chains that decay by both alpha and beat radition. 


Joseph Bevelacqua

Uranium and Thorium decay products are predominately an internal 

hazard. Historically, the radiological concerns of uranium have 

been overshadowed by the chemical toxicity of uranium to the: 

A) lymph nodes 

B) lung 

C) bone marrow 

D) liver 

E) kidney 


Uranium, a heavy metal is chemically toxic to the kidneys. 


Joseph Bevelaqua

The minimum mass of material which sustains a nuclear chain 

reaction for a given set of conditions is called: 

A) mass defect 

B) critical mass 

C) enriched mass 

D) keff mass 

E) fissile material 


Critical mass depends on the fissile isotope, the isotopes 

enrichment, its geometry and the presence and types of moderator 

and reflector material. 


Joseph Beleacqua

The relationship between the mass of radioactive material and the 

activity of a material is: 

A) specific activity 

B) decay constant 

C) source activity 

D) transformation constant 

E) plancks constant 


Health Physics and Radiological Health Handbook, 

Page 264

The reason radioactive compounds are often mixed with quantities 

of non-radioactive but chemically identical material is to: 

A) allow scientists to test the non-radioactive 

component of the compound 

B) increase the compounds specific activity so 

that small losses of compound will not affect 

the radioactivity of the compound 

C) increase the amount of compound to work with, 

making measurement easier, decreasing the 

statistical probability of error 

D) ensure that enough of the compound will be 

available to run a number of analysis before 

decaying seven half lives 

E) ensure that the loss of small amounts of 

compound will have a small affect on the 

radioactivity of the compound 


The use of a carrier ensures that only a very small fraction of 

molecules of the compound contain the radioisotope, so that if 

small amounts of the compound are lost through adsorption and so 

on, the amount of radioactivity lost will be negligible. 

Introduction to Radiochemistry 

David Malcolme-Lawes

The NRC defines a hot particle as a: 

A) discrete radioactive fragment that is 

insoluble in water, is less than 1 cm and 

exhibits a dose rate of > 100 mrad/hr 

B) small radioactive particle that is soluble in 

water and is less than 1 mm 

C) discrete radioactive fragment that is 

insoluble in water and is less than 1 mm 

D) small radioactive particle that is insoluble 

in water, is less the 1/4" and exhibits a 

dose rate of > 50 mrad/hr 

E) discrete radioactive particle that is < 1 mm 

and exhibits a dose rate of > 100 mrad/hr at 

1 inch 


NRC Information notice IN 90-48

The electron volt is a unit of energy and is defined as: 

A) 33.7 ergs 

B) 100 ergs 

C) 2.25 E-19 kw-hr 

D) 1.6 E-19 joule 

E) 1.0 E-12 coulombs 


Introduction to Health Physics 

Cember

Uptake and retention of a radionuclide is influenced by all of 

the following EXCEPT: 

A) portal of entry 

B) chemical property of radionuclide 

C) solubility 

D) radioactive half-life 

E) particle size 


All the factors are a component of the biological half-life for 

the radionuclide 

NCRP 65

An individual has received an uptake of Co-60 by inhalation. The 

approximate time it takes for the particle to traverse the 

trachea is: 

A) 4 hours 

B) 1 day 

C) 0.1 hour 

D) 1 hour 

E) 3 hours 


NCRP 65. Clearance times for the respiratory tract are: Trachea: 

0.1 hr Bronchi: 1.0 hour Bronchioles: 4.0 hours Alveoli: 10 to 

1500+ days

An active person who eats a high fiber diet and has adequate 

fluids will have a gastrointestinal tract transit time of: 

A) 24 to 36 hours 

B) 4 to 6 hours 

C) 5 days or longer 

D) 10 to 12 hours 

E) 2 to 3 days 


Mean emptying time for stomach 1 hour, small intestine 4 hour, 

upper large intestine 13 - 20 hours, and lower large intestine 24 

hours 

NCRP 65

In accidents that release fission products, radioactive iodine 

uptake by the thyroid can be checked by holding a beta-gamma 

survey probe over the thyroid. Peak thyroid uptake values will 

not be reached until ___ after exposure. 

A) 2 hours 

B) 12 hours 

C) 2 days 

D) 30 minutes 

E) 36 hours 


NCRP 65

Cesium-137 decays by emitting: 

A) two gammas: 1.17 Mev and 1.13 Mev 

B) two betas: 0.51 Mev and 1.17 Mev 

C) one gamma: 0.662 Mev 

D) one positron: 0.662 Mev 

E) alpha and gamma at 0.662 Mev 


Cs-137 decays by emitting beta particles of two different 

energies, 0.51 Mev (95%) and 1.17 Mev (5%) and is accompanied by 

a 0.662 Mev gamma from its daughter product Ba-137m.

A gram-atomic weight of an element contains: 

A) 3.011 E13 atoms 

B) 3.7 E23 molecules 

C) 1.24 E10 atoms 

D) 6.022 E23 atoms 

E) 2.22 E12 atoms 


Avogados number: 6.022 E23 or a mole 


A mole of U-238 weighs: 

A) 238 amu 

B) 92 amu 

C) 92 grams 

D) 1 gram 

E) 238 grams 



CS-134, Cs-137 and Cs-135 are: 

A) isotopes 

B) isotones 

C) isomers 

D) isobars 

E) isometrics 


Isotopes have the same number of protons or atomic number 


The SI unit of energy is: 

A) Sievert 

B) Roentgen 

C) Watt 

D) BTU 

E) Joule 



All of the following are naturally occuring radionuclides EXCEPT: 

A) K-40 

B) Sm-147 

C) Re-187 

D) Pu-241 

E) Th-232 


Pu-241 is part of the Neptunium series which is artificially 

produced. 


The nucleus transfers its energy to an orbital electron, which is 

then ejected at a discrete energy. This decay mode is called: 

A) isomar 

B) positron 

C) beta 

D) characteristic 

E) internal conversion 


The ejection of the electron can cause secondary radiation; an 

electron will transition to the "vacancy" releasing a 

characteristic x-ray to go to a lower energy state. This x-ray 

can go on to interact with an electron in the atom causing it to 

be ejected producing an auger electron. 


Xe-133 undergoes isomeric transition, the daughter product is: 

A) Cs-133 

B) Te-133 

C) Xe-133 

D) I-134 

E) I-133 


Isomeric transition involves an radionuclide existing in a 

metastable state. When it transitions to a stable state it emits 

a gamma and is the same element. 


The formula for calculating specific activity is: 

A) lambda * N 

B) (lambda * N) / g 

C) (lambda * g) / N 

D) N * g / lambda 

E) g * lambda 


Specific activity is equal to decay constnat (lambda) times 

number of atoms (N) in a gram. 


Specific activity units are: 

A) joules/kg 

B) gram/curie 

C) curie/gram 

D) ergs/gram 

E) ergs/cm 


Specific activity is equal to decay constant times number of 

atoms in a gram.

A radionuclide with a parent half-life longer than that of the 

daughter is in transient equilibrium. The ratio of the number of 

parents atoms to the number of daughter atoms is: 

A) doubled 

B) reduced by half 

C) increases by a factor of ten 

D) constant 

E) decreasing by the natural log of 2 


In this case the daughter activity decays at the same rate as the 

parent activity. "the formation rate of daughter atoms equals the 

decay rate of daughter atoms" 


You have counted a radioactive sample every hour for a period of 

twelve hours. A plot of the count rate versus time on a semi-log 

graph reveals a curved decay line. This indicates: 

A) an isotope with a short half-life 

B) an isotope with a long half life 

C) a counting error has occured 

D) only one radionuclide is present 

E) more than one radionuclide is present 


On a semi-log graph a plot of a single radionuclide decaying will 

be a straight line. More than one radionuclide with differing 

half-lives will give a curved line based on total counts 

obtained. 


As an alpha particle transverses a substance, the ionization of 

the particle produces: 

A) increases as the particle loses energy 

B) decreases lineraly as the particle loses 

energy 

C) remains constant as the particle loses energy 

D) is independent of the energy of the particle 

E) decreases exponentially as the particle loses 

energy 


Ionization gradually increases as the particle loses energy, 

until the ionization reaches a peak value and drops to zero as 

all the alpha energy is lost. 


For an alpha particle to penetrate the dead layer of skin it must 

have an energy of at least: 

A) 2 Mev 

B) 70 kev 

C) 7.5 Mev 

D) 5 Mev 

E) 100 kev 


Moe, Operational Health Physics Training, pages 3-8

The average energy of a positron emitted during positron decay 

is: 

A) 1/3 

B) 1/4 

C) 4/10 

D) 1/2 

E) 3/4 


For positrons it is 4/10 or 0.4 of the maximum energy. 


Bremsstrahlung predominantly occurs at beat energies greater 

than: 

A) 6 Mev 

B) 1 Mev 

C) 70 kev 

D) 100 kev 

E) 2 Mev 



The stopping power for electrons ______ as the atomic number of 

the absorber _______. 

A) decreases, decreases 

B) increases, decreases 

C) increases, increases 

D) is constant, increases 

E) decreases, increases 


This occurs because substances of high z have fewer electrons per 

gram and these are more tightly bound. Consequently, the range 

tends to increase as z increases. 

Moe, Operational Health Physics Training, pages 3-15

The binding energy of a neutron in any element is: 

A) 33.7 ev 

B) 100 kev 

C) 70 kev 

D) 2 Mev 

E) 8 Mev 


This is the energy which holds a neutron in the nucleus except 

for the lighter nuclei. To remove the neuton one must supply at 

least this much energy. 


Kerma is the sum of the initial kinetic energy of all charged 

ionizing particles liberated by: 

A) photoelectric effect 

B) pair production 

C) uncharged ionizing radiation 

D) elastic scattering 

E) ionization 


The Health Physics and Radiological Health Handbook 1992

The Quality factor (Q) in H=DQN is an assigned factor for 

radition protection applications that denotes the modification of 

the effectiveness of a given absorbed dose. The numerical value 

of Q is based partly on: 

A) biological effects and experimental results 

B) observed effects and legal requirements 

C) experimental results and observed effects 

D) biological effects and judgement 

E) observed effects and judgement 


The quality factor is not experimently determined, it is an 

assigned value based on dose modifying factors; Q is for 

radiation protection apllications; that is, for relatively low 

dose rates, not for use in radiobiology or experiments, and not 

for acute accidental exposures. 


The term used to describe a process in which a number of light 

fragments are emitted from an excited nucleus is: 

A) spallation 

B) kerma 

C) fission 

D) fragmentation 

E) scattering 



An individual living in Denver, Colorado (elevation 5280 ft above 

sea level) could expect to receive an average annual dose 

equivalent due to cosmic radiation of approximately: 

A) 13 mrem 

B) 26 mrem 

C) 50 mrem 

D) 76 mrem 

E) 200 mrem 


Cosmic radiation accounts for approximately 26 mrem annual 

average dose equivalent at sea level in the U.S. Each 2000 meter 

increase in altitude above sea level roughly doubles this value. 

(NCRP 93)

Rn-220 is a member of which of the following decay series? 

A) Uranium 

B) Thorium 

C) Actinium 

D) Neptunium 

E) Radium 


Thorium is the 4n series. The mass number 220 is divisible 

evenly by 4 (220 / 4 = 55, no remainder).

The most predominant constituent of primary cosmic radiation is: 

A) Alpha particles 

B) Neutrons 

C) Electrons 

D) Mesons 

E) Protons 


Primary cosmic radiation consists of approximately 87% high 

energy protons, 12% alpha particles, and 1% other nuclei. 

Gollnick, 3rd Edition, Page 157

Which of the following naturally occuring radionuclides 

contributes the most to the annual average background dose 

equivalent to a member of the U.S. due to ingestion? 

A) Th-232 

B) Rn-222 

C) Ra-226 

D) K-40 

E) C-14 


About 80% of our internal dose from ingestion of naturally 

occuring radionuclides is due to K-40. 


One roentgen of gamma radiation deposits approximatley how much 

energy in soft tissue? 

A) 87 erg/gm 

B) 33.7 ev/gm 

C) 1 J/Kg 

D) 2.58 E-4 c/Kg 

E) 98 erg/gm 


One R deposits approximately 87 erg/gm in air and creates an 

electrical charge of 2.58 E-4 c/Kg in air.

An absorbed dose of 3 rad results in an energy deposition of: 

A) 3E-2 J/Kg 

B) 1E-3 erg/gm 

C) 3.3E-3 J/kg 

D) 3E-2 J/gm 

E) 1E-2 erg/Kg 


(3 rad)(1 gray/100 rad)(1 J/Kg/gray) 

= 3E-2 J/Kg

Why is it acceptable to establish gamma dose equivalent rates 

(mrem/hr) using an exposure rate instrument that reads out in 

mR/hr? 

A) A conversion factor relating mR to mrem is 

always applied. 

B) One mR/hr is roughly equivalent to one 

mrem/hr for photons in tissue. 

C) Exposure rate instruments are constructed of 

tissue equivalent materials. 

D) In tissue, one roentgen of photons deposits 

exactly the same energy as one rad of 

photons. 

E) There is only a 10% difference between a 

reading of one mR/hr and one mrem/hr for 

photons in tissue. 


One roentgen deposits 98 erg/gm in tissues roughly equivalent to 

the 100 erg/gm deposited by one rad. One rad = one rem for gamma 

photons, so one R = one rem for photons in tissue.

Which of the following is equivalent to 475 mC: of activity? 

A) 1.06 E 1 MBq 

B) 1.76 E-2 MBq 

C) 1.06 E 1 TBq 

D) 1.76 E 4 TBq 

E) 1.76 E-2 TBq 


(475 mCi)(Ci/1E3 mCi)(3.7E 10 Bq/Ci)(TBq/1E1Z Bq) 

= 1.76 E-2 TBq

The approximate diameter of an atomic nucleus is: 

A) 1 E-12 cm 

B) 1 E-8 cm 

C) 1 E-12 m 

D) 1 E-10 m 

E) 1 E-8 m 


The diameter of the nucleus is roughly 1 E-12 cm, while the 

diameter of the entire atom is roughly 

1 E-8 cm. 


The electron volt is: 

A) a unit of power equal to 1.6 E-19 joules per 

second 

B) a unit of energy equal to 1.6 E-19 joules 

C) a unit of electrostatic charge equal to 

1.6 E-19 coulombs 

D) a unit of electrical capacitance equal to 

1.6 E-19 coulomb per volt 

E) a unit of energy equal to 1.6 E-19 ergs 


An electron volt is an unit of energy equal to 1.6 E-19 joules

An unstable atom with an excess of protons in the nucleus could 

be expected to decay by which of the following? 

A) alpha 

B) electron capture 

C) beta plus 

D) electron capture or beta plus 

E) electron capture, beta plus, or alpha 


All are possible, especially in high Z materials.

Which of the following does NOT affect the mode of radioactive 

decay: 

A) Neutron to proton ratio is too high 

B) Neutron to proton ratio is too low 

C) The amount of excess energy of the parent 

D) The atomic mass of the parent 

E) The electron quantum state 


Radioactive decay is affected only by conditions within the 

nucleus.

Radon gas can be found in which of the following decay chains? 

A) Thorium 

B) Uranium 

C) Actinium 

D) All of the above 

E) None of the above 


Radon 220, 222, 219 are found in the Thorium, Uranium and 

Actinium decay chains respectively.

If the half life of a radionuclide is 10 days, the tenth life 

would be about: 

A) 3 days 

B) 7 days 

C) 14 days 

D) 33 days 

E) 100 days 


In order to calculate the 1/10 life, multiply the half by 3.32. 

3.32 is the ratio of 1n 10/1n 2, 2.3/.693 = 3.32.

Which of the following is true for a charged particle traveling 

through a material? 

A) The linear rate of energy loss is directly 

proportional to the electrical charge and 

inversely proportional to the velocity 

B) The linear rate of energy loss is directly 

proportional to the velocity and inversely 

proportional to the electrical charge 

C) The linear rate of energy loss is directly 

proportional to the velocity and electrical 

charge 

D) The linear rate of energy loss is inversely 

proportional to the velocity and electrical 

charge 

E) Answering this question correctly is directly 

proportional to my understanding of the 

question and indirectly proportional to my 

knowledge 


Multiple-charged particles will lose energy more rapidly than 

singly-charged particles. As charged particles slow down, they 

give up energy more readily.

Which of the following is the BEST definition of photon 

attenuation? 

A) Attenuation is the reduction in photon 

intensity by the processes of ionization and 

excitation interactions 

B) Attenuation is the reduction in photon 

intensity by geometry and shielding 

configuration 

C) Attentuation is the reduction in photon 

intensity by compton interactions 

D) Attenuation is the reduction in photon 

intensity by scattering and absorption 

processes 

E) Attenuation is the reduction in photon 

intensity by photoelectric interactions 


The absorption occurs via the photoelectron, compton electron 

and the pair production electron. Scattering results from the 

compton photon and the pair production annihilation photon.

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