National Registry of Radiation Protection Technicians (NRRPT) Exam — Questions and Answers

Question 1: What should be done with contaminated PPE?

Thrown in trash
Washed with regular laundry
Reused immediately
Stored in radioactive waste containers (Correct answer)

Correct answer: Stored in radioactive waste containers

Contaminated Personal Protective Equipment (PPE) must be treated as radioactive waste to prevent the spread of contamination. After careful removal to avoid further contamination, it should be placed into designated radioactive waste containers. This ensures proper segregation, storage, and eventual disposal according to strict regulatory guidelines for radioactive waste management.

Question 2: Which federal agency has authority over the transport of radioactive materials in commerce, including hospital radiopharmaceutical deliveries?

DOT (Correct answer)
FDA
EPA
NRC

Correct answer: DOT

The Department of Transportation (DOT) regulates the packaging, labeling, and transportation of radioactive materials in commerce under 49 CFR Parts 171-180.

Question 3: Which NRC regulation establishes radiation protection programs for nuclear power plants?

10 CFR Part 50
10 CFR Part 20 (Correct answer)
10 CFR Part 71
10 CFR Part 19

Correct answer: 10 CFR Part 20

10 CFR Part 20 establishes standards for protection against radiation applicable to all NRC licensees, including nuclear power plants.

Question 4: Which OSHA standard addresses bloodborne pathogen exposure control plans that may intersect with radiation safety in interventional suites?

29 CFR 1910.147
29 CFR 1910.1030 (Correct answer)
29 CFR 1910.1200
29 CFR 1910.134

Correct answer: 29 CFR 1910.1030

29 CFR 1910.1030 is OSHA's Bloodborne Pathogens Standard, which requires exposure control plans relevant where radiation procedures involve patient blood contact.

Question 5: During radiological work planning, what is the primary benefit of performing a mockup or dry run of a task?

To identify procedural inefficiencies and reduce actual time—and therefore dose—in the radiation field (Correct answer)
To verify that protective equipment fits correctly
To calibrate dosimeters before actual exposure
To satisfy NRC documentation requirements for complex tasks

Correct answer: To identify procedural inefficiencies and reduce actual time—and therefore dose—in the radiation field

Mockups allow workers to practice a task and optimize their technique before entering the radiation field, directly reducing the time spent in the field and thus the total dose received.

Question 6: An alpha particle and a beta particle have the same kinetic energy. Which particle will have a shorter range in tissue and why?

The beta particle, because it is smaller and less likely to interact.
The alpha particle, because of its higher mass and charge, leading to a higher rate of energy loss. (Correct answer)
The beta particle, because it follows a more tortuous path.
They will have the same range because their kinetic energy is identical.

Correct answer: The alpha particle, because of its higher mass and charge, leading to a higher rate of energy loss.

Alpha particles are much more massive (approx. 7300 times an electron) and have a +2 charge, compared to a beta particle's -1 charge. This results in a much higher specific ionization and linear energy transfer (LET). Consequently, alpha particles lose their energy over a much shorter distance in matter compared to beta particles of the same initial kinetic energy.

Question 7: An area is surveyed and found to have a radiation level that could result in an individual receiving a dose equivalent in excess of 100 mrem in 1 hour at 30 centimeters from the source. According to 10 CFR 20, how must this area be posted?

DANGER, HIGH RADIATION AREA (Correct answer)
CAUTION, RADIATION AREA
CAUTION, RADIOACTIVE MATERIAL
GRAVE DANGER, VERY HIGH RADIATION AREA

Correct answer: DANGER, HIGH RADIATION AREA

10 CFR 20.1902 requires that an area where an individual could receive a dose equivalent in excess of 0.1 rem (100 mrem) in 1 hour at 30 cm from the source must be posted as a "CAUTION, HIGH RADIATION AREA" or "DANGER, HIGH RADIATION AREA".

Question 8: Cementation, bituminization, and polymer impregnation are all examples of which radioactive waste treatment process?

Volume reduction
Decontamination
Thermal treatment
Solidification/stabilization (Correct answer)

Correct answer: Solidification/stabilization

Solidification/stabilization processes immobilize radionuclides in a solid matrix, reducing leachability and improving waste form stability for long-term disposal.

Question 9: How long should radiation exposure records be retained?

1 year
Until inspection is complete
5 years
Lifetime of employment + 30 years (Correct answer)

Correct answer: Lifetime of employment + 30 years

Radiation exposure records must be retained for the lifetime of an individual's employment plus 30 years. This extended retention period is crucial for long-term health monitoring, as potential radiation effects can manifest many years after exposure, and for demonstrating continuous regulatory compliance.

Question 10: Which of the following best describes the function of a dosimeter alarming at its set point during radiological work?

Alerts the worker that a pre-set dose or dose rate threshold has been reached (Correct answer)
Signals that the dosimeter battery is low
Confirms that background radiation levels are normal
Indicates the worker has received a lethal dose

Correct answer: Alerts the worker that a pre-set dose or dose rate threshold has been reached

Electronic personal dosimeters alarm at pre-set dose or dose rate thresholds to warn workers before they exceed planned exposure limits.

Question 11: Why is area zoning important in contamination control?

To contain contamination (Correct answer)
For room aesthetics
To reduce lighting costs
To display art

Correct answer: To contain contamination

Area zoning involves dividing a facility into different zones (e.g., clean, buffer, contaminated) based on the potential for radioactive contamination. This practice is crucial for contamination control as it physically contains radioactive materials within designated areas, preventing their spread to uncontaminated spaces. It also facilitates controlled access and systematic decontamination efforts.

Question 12: The nuclide Am-241 is commonly used in smoke detectors because it emits:

Gamma rays that activate a photovoltaic sensor
Neutrons that activate a BF₃ detector tube
Alpha particles that ionize air in an ionization chamber (Correct answer)
Beta particles that ionize a smoke-sensing gas

Correct answer: Alpha particles that ionize air in an ionization chamber

Am-241 emits 5.49 MeV alpha particles that ionize air between two electrodes; smoke particles reduce this ionization current, triggering the alarm.

Question 13: Which document must accompany a shipment of radioactive material when transported by highway in the US?

Shipping papers (Hazmat manifest) (Correct answer)
Bioassay report
ALARA Action Plan
Radiation Work Permit

Correct answer: Shipping papers (Hazmat manifest)

DOT regulations (49 CFR) require shipping papers describing the radioactive material to accompany all hazmat highway shipments.

Question 14: Which of the following personal dosimeters uses a crystalline solid that, when heated after exposure to ionizing radiation, emits light proportional to the dose received?

Optically Stimulated Luminescence (OSL) Dosimeter
Film Badge
Pocket Ionization Chamber
Thermoluminescent Dosimeter (TLD) (Correct answer)

Correct answer: Thermoluminescent Dosimeter (TLD)

A Thermoluminescent Dosimeter (TLD) contains a crystalline material (like Lithium Fluoride) that traps energy from ionizing radiation. When heated, this stored energy is released as visible light, and the amount of light is proportional to the radiation dose absorbed by the crystal.

Question 15: A 'hot particle' is particularly hazardous because it:

Emits high-energy gamma rays that penetrate shielding
Produces neutron activation of surrounding materials
Delivers a highly localized dose to a small area of skin or tissue (Correct answer)
Travels rapidly through the body and accumulates in the thyroid

Correct answer: Delivers a highly localized dose to a small area of skin or tissue

Hot particles deliver an extremely high local dose rate to a microscopic area of skin or tissue, potentially exceeding skin dose limits even when whole-body dose is low.

Question 16: Under DOT regulations, a Type A quantity of radioactive material is defined as:

Material with a specific activity greater than 70 TBq/kg
Any exempt quantity approved by the NRC
Any quantity requiring a Type B package for transport
A quantity not exceeding the A1 or A2 value for the radionuclide (Correct answer)

Correct answer: A quantity not exceeding the A1 or A2 value for the radionuclide

Type A quantities are at or below the A1 (special form) or A2 (normal form) values, which represent the maximum allowed in a Type A package.

Question 17: Which dosimeter type uses lithium fluoride (LiF) crystals to measure accumulated radiation dose?

Film badge
Pocket ionization chamber
Thermoluminescent dosimeter (TLD) (Correct answer)
Optically stimulated luminescence (OSL)

Correct answer: Thermoluminescent dosimeter (TLD)

TLDs use lithium fluoride crystals that store energy from radiation and release it as light when heated, proportional to dose received.

Question 18: Which detector is most appropriate for measuring neutron dose equivalent in a mixed neutron-gamma field?

Standard GM tube
Silicon PIN diode
Proportional counter with BF3 or He-3 fill gas (Correct answer)
NaI(Tl) scintillator

Correct answer: Proportional counter with BF3 or He-3 fill gas

BF3 and He-3 proportional counters are neutron-sensitive via (n,α) and (n,p) reactions respectively, making them standard choices for neutron detection.

Question 19: What is the primary purpose of a 'step-off pad' at a radiological boundary?

To absorb alpha radiation before workers exit
To provide a clean surface for removing protective footwear and preventing contamination spread (Correct answer)
To shield workers from direct radiation shine
To collect air samples near the boundary

Correct answer: To provide a clean surface for removing protective footwear and preventing contamination spread

Step-off pads provide a clean zone where workers can remove contaminated shoe covers without tracking contamination into clean areas.

Question 20: The 'plume exposure pathway' in nuclear emergency planning refers primarily to doses from which source?

Ingestion of contaminated food and water over months
External exposure from ground deposition over years
Direct irradiation and inhalation during the passage of a radioactive cloud (Correct answer)
Submersion in contaminated water bodies

Correct answer: Direct irradiation and inhalation during the passage of a radioactive cloud

The plume exposure pathway encompasses cloudshine and inhalation exposure during passage of the initial radioactive plume.

Question 21: A direct-reading pocket dosimeter reads 0 mR at the start of a shift and 340 mR at the end. If the worker's legal dose limit is 1250 mR/quarter, what percentage of the quarterly limit was used?

27.2% (Correct answer)
34.0%
13.6%
68.0%

Correct answer: 27.2%

340 mR ÷ 1250 mR × 100 = 27.2% of the quarterly limit was used.

Question 22: Under 49 CFR (DOT), a radioactive material package labeled 'Radioactive II' indicates the transport index (TI) is:

Zero
Greater than 10
Greater than 0 but not exceeding 1 (Correct answer)
Greater than 1 but not exceeding 10

Correct answer: Greater than 0 but not exceeding 1

A Radioactive II label is required when the TI is greater than 0 but does not exceed 1, indicating a limited dose rate at 1 meter from the package surface.

Question 23: Which of the following best describes the purpose of a nuclear track etch dosimeter (e.g., CR-39)?

Detecting alpha contamination on surfaces
Real-time gamma dose rate monitoring
Measuring low-energy beta particle doses
Measuring fast neutron doses through recoil proton tracks in plastic (Correct answer)

Correct answer: Measuring fast neutron doses through recoil proton tracks in plastic

CR-39 track etch dosimeters measure fast neutron doses by detecting the tracks left by recoil protons produced when neutrons interact with hydrogen atoms in the plastic.

Question 24: Which bioassay technique is used to assess internal contamination by measuring radiation emitted directly from the body?

Whole-body counting (in-vivo counting) (Correct answer)
Fecal sample gamma counting
Nasal swab analysis
Urinalysis with gamma spectrometry

Correct answer: Whole-body counting (in-vivo counting)

Whole-body counting detects gamma-emitting radionuclides inside the body by measuring radiation emanating directly through the body surface.

Question 25: A radiological posting reading 'Radiation Area' (per NRC 10 CFR 20) indicates a dose rate of at least:

100 mrem/hr at 1 meter
2 mrem/hr at 30 cm
5 mrem/hr at any point 30 cm from the source or surface (Correct answer)
5 mrem/hr at 30 cm

Correct answer: 5 mrem/hr at any point 30 cm from the source or surface

NRC regulations define a Radiation Area as any area where dose rate exceeds 5 mrem/hr (0.05 mSv/hr) at 30 cm from the source or accessible surface.

Question 26: According to 10 CFR 20.1904, what action is required before disposing of an empty, uncontaminated container that previously held radioactive material?

The radioactive material label must be removed or defaced. (Correct answer)
The container must be filled with shielding material.
The container must be stored for a period of ten half-lives.
A final radiation survey must be attached to the container.

Correct answer: The radioactive material label must be removed or defaced.

10 CFR 20.1904(b) states that prior to the removal or disposal of empty uncontaminated containers to unrestricted areas, the licensee must remove or deface the radioactive material label or otherwise clearly indicate that the container no longer contains radioactive materials.

Question 27: Why must incident reports be filed?

For insurance claims
To improve safety protocols (Correct answer)
To penalize workers
To satisfy surveys

Correct answer: To improve safety protocols

Incident reports are vital tools for identifying hazards, analyzing root causes of accidents or near-misses, and implementing corrective actions. By thoroughly documenting incidents, healthcare facilities can learn from mistakes, revise safety protocols, and prevent similar events from occurring in the future. This continuous improvement cycle enhances overall safety performance and patient care.

Question 28: Under NRC regulations, which document must a healthcare facility post in a conspicuous location accessible to radiation workers?

Emergency action plan
NRC Form 3 — Notice to Employees (Correct answer)
Annual dose summary report
Radiation survey log

Correct answer: NRC Form 3 — Notice to Employees

NRC Form 3 (Notice to Employees) must be posted where it can be seen by workers subject to NRC regulations, per 10 CFR 19.11.

Question 29: What is the primary purpose of maintaining a negative pressure differential in a radiological containment enclosure, such as a glovebox or hot cell, relative to the surrounding room?

To provide a constant flow of fresh air to cool internal components.
To increase the efficiency of the HEPA filters by creating higher airflow.
To reduce the external radiation dose rate for personnel outside the containment.
To ensure that any potential leakage flows from the surrounding room into the containment. (Correct answer)

Correct answer: To ensure that any potential leakage flows from the surrounding room into the containment.

Maintaining negative pressure ensures that the direction of airflow is always from the cleaner area (the surrounding room) into the more contaminated area (the containment). This engineering control prevents the out-leakage and spread of airborne radioactive contaminants should there be a breach in the containment.

Question 30: A nuclear power plant declares a 'General Emergency.' What immediate protective action recommendation is typically made for the public within 2 miles?

Take potassium iodide tablets only
No action required; monitor official notifications
Shelter-in-place with windows and doors closed
Evacuate immediately (Correct answer)

Correct answer: Evacuate immediately

A General Emergency implies imminent or actual substantial release; immediate evacuation within 2 miles (the inner EPZ) is the standard initial protective action.

Question 31: Which type of radiation has the greatest penetrating power in matter?

Alpha particles
Thermal neutrons
Beta particles
High-energy gamma rays (Correct answer)

Correct answer: High-energy gamma rays

High-energy gamma rays are highly penetrating because they are uncharged photons that interact only probabilistically; thick dense shielding is required to attenuate them significantly.

Question 32: What is the purpose of posting a 'Radioactive Material' area sign per 10 CFR 20?

To warn individuals that quantities of radioactive material exceeding certain thresholds are present (Correct answer)
To indicate the area contains more than 10 times the quantity of radioactive material specified in Appendix C to Part 20
To alert workers that dose rates exceed 100 mrem/hr
To designate areas where radioactive waste is stored pending disposal

Correct answer: To warn individuals that quantities of radioactive material exceeding certain thresholds are present

Radioactive Material area postings warn personnel that quantities of radioactive material above regulatory thresholds specified in 10 CFR 20 Appendix C are present.

Question 33: What is the correct sequence for donning personal protective equipment (PPE) when entering a contaminated area?

Coveralls → inner gloves → booties → outer gloves → respirator
Respirator → coveralls → inner gloves → booties → outer gloves (Correct answer)
Inner gloves → coveralls → booties → respirator → outer gloves
Outer gloves → inner gloves → coveralls → booties → respirator

Correct answer: Respirator → coveralls → inner gloves → booties → outer gloves

Respirator is donned first to protect airways before other PPE is put on, followed by coveralls, gloves, and booties to minimize contamination risk during donning.

Question 34: Which of the following best describes a 'dirty bomb' (RDD) from a radiation protection standpoint?

A radiological source placed in a populated area without explosion
A device that causes a criticality accident in a public space
A nuclear weapon with reduced yield designed to minimize blast effects
A conventional explosive combined with radioactive material designed to disperse contamination (Correct answer)

Correct answer: A conventional explosive combined with radioactive material designed to disperse contamination

An RDD uses conventional explosives to disperse radioactive material; its primary effect is contamination and psychological impact, not nuclear yield.

Question 35: A licensee's bioassay program detects tritium (H-3) in a worker's urine at 40,000 dpm/mL. The first required action is to:

Notify the NRC within 24 hours
Immediately suspend the worker from all radiation work
Estimate the intake and calculate the committed effective dose equivalent (Correct answer)
Repeat the urine sample collection after 30 days

Correct answer: Estimate the intake and calculate the committed effective dose equivalent

When bioassay detects internal contamination, the first step is to estimate the intake using appropriate metabolic models and calculate the resulting CEDE to determine if regulatory limits were exceeded.

Question 36: A radiation protection technician is selecting shielding for a high-energy beta-emitting source. To minimize the production of Bremsstrahlung radiation, what type of material should be used as the primary shield?

Any material is sufficient as long as it is thick enough to stop the betas
A thin layer of cadmium followed by a thick layer of lead
Low-Z material, such as plastic or aluminum (Correct answer)
High-Z material, such as lead

Correct answer: Low-Z material, such as plastic or aluminum

Bremsstrahlung (braking radiation) is produced when beta particles (electrons) decelerate rapidly in a material. The production of these secondary x-rays is proportional to the atomic number (Z) of the shielding material. Therefore, a low-Z material like plastic or aluminum should be used as the primary shield to stop the beta particles, which minimizes Bremsstrahlung production. A high-Z material can then be placed after the low-Z shield to attenuate any Bremsstrahlung that is created.

Question 37: The ALARA principle as applied to radioactive waste management means:

All waste must be disposed of within 1 year of generation
Only licensed personnel may handle any quantity of radioactive waste
Activity levels must be reduced to zero before disposal
Waste generation, worker doses during handling, and public doses should be minimized as reasonably achievable (Correct answer)

Correct answer: Waste generation, worker doses during handling, and public doses should be minimized as reasonably achievable

ALARA (As Low As Reasonably Achievable) applied to waste management requires optimizing processes to minimize both waste generation and radiation doses during handling, storage, and disposal.

Question 38: A smear survey shows 450 dpm/100 cm² of beta activity on an uncontrolled surface. What action is required per NRC guidelines?

No action needed; below all limits
Post a Caution - Radioactive Material sign and restrict access (Correct answer)
Evacuate the area and notify the NRC immediately
Decontaminate immediately; the level exceeds the 5,000 dpm/100 cm² limit but not the emergency threshold

Correct answer: Post a Caution - Radioactive Material sign and restrict access

NRC surface contamination limits for unrestricted areas are 1,000 dpm/100 cm² (beta/gamma); 450 dpm/100 cm² exceeds this, requiring posting and restriction.

Question 39: Which of the following best describes the 'doffing' sequence for protective clothing to minimize self-contamination?

Remove hood first to allow full visibility, then gloves, then coveralls
Remove outer gloves first, then hood, then booties, then coveralls, rolling outward as removed (Correct answer)
The sequence does not matter as long as all items are removed before the frisker check
Remove coveralls first, then booties, then outer gloves, then hood

Correct answer: Remove outer gloves first, then hood, then booties, then coveralls, rolling outward as removed

Proper doffing removes outer gloves first to enable clean handling of other items, then proceeds systematically rolling contaminated surfaces inward to prevent spread.

Question 40: What is the derived air concentration (DAC) used for in internal dosimetry?

To measure stack effluent activity
To calibrate air samplers
To establish the airborne concentration that equals one ALI when inhaled for a full work year (Correct answer)
To set external dose rate limits in controlled areas

Correct answer: To establish the airborne concentration that equals one ALI when inhaled for a full work year

The DAC is the airborne radionuclide concentration that, if breathed for 2,000 hours, would deliver one annual limit on intake (ALI).

Question 41: A Derived Air Concentration (DAC) for an inhalation pathway is defined as the airborne concentration that, if breathed for:

8 hours at work rate breathing, results in intake of 1 ALI
40 hours per week at light activity, results in 5 rem dose
100 hours cumulatively, results in 500 mrem
2000 hours per year at work rate breathing, results in intake of 1 ALI (Correct answer)

Correct answer: 2000 hours per year at work rate breathing, results in intake of 1 ALI

DAC is the airborne concentration of a radionuclide that, if inhaled for a full work year (2000 hours) at light work breathing rate, would result in intake of 1 ALI.

Question 42: During decontamination of a wound with embedded radioactive foreign material, what is the recommended initial action?

Irrigate the wound copiously with sterile saline (Correct answer)
Pack the wound with lead shielding material
Leave the wound undisturbed until a radiochemist arrives
Apply a tourniquet proximal to the wound

Correct answer: Irrigate the wound copiously with sterile saline

Copious irrigation with sterile saline removes loose contamination and reduces internal uptake while awaiting medical and HP guidance.

Question 43: Which type of bioassay measures radioactivity directly in the body using external detectors?

In-vivo bioassay (Correct answer)
In-vitro bioassay
Excretion bioassay
Indirect bioassay

Correct answer: In-vivo bioassay

In-vivo bioassay uses whole-body or lung counters to directly detect gamma and X-ray emissions from radionuclides inside the body.

Question 44: What is the first action after a contamination incident?

Clean with a towel
Ventilate the room
Ignore and continue
Report and contain the area (Correct answer)

Correct answer: Report and contain the area

The immediate first action after a contamination incident is to report it to the appropriate supervisor or Radiation Safety Officer and then contain the area to prevent further spread of radioactive material. This ensures that proper response procedures can be initiated promptly, minimizes potential exposure to others, and facilitates effective cleanup and control.

Question 45: Which regulatory body oversees the approval and licensing of radiopharmaceuticals used in nuclear medicine departments?

EPA
FDA (Correct answer)
NRC
DOT

Correct answer: FDA

The FDA approves radiopharmaceuticals as drugs or biologics under the Federal Food, Drug, and Cosmetic Act before they can be commercially manufactured and distributed for patient use.

Question 46: Which method is typically used for skin decontamination?

Scrubbing with alcohol
Soap and water wash (Correct answer)
Applying wax
Using a fire hose

Correct answer: Soap and water wash

For most external skin contamination, a gentle wash with mild soap and lukewarm water is the recommended method for decontamination. This approach helps to physically remove radioactive particles from the skin without causing irritation or abrasion, which could potentially facilitate the absorption of radioactive material into the body. Multiple washes may be necessary.

Question 47: A hospital's radiation therapy department discovers a brachytherapy source is unaccounted for. Under NRC regulations, when must this loss be reported?

Within 30 days of discovering the loss
Only if the source is not found within 7 days
Within 4 hours if dose rate exceeds certain limits; within 24 hours for other cases (Correct answer)
At the next Radiation Safety Committee meeting

Correct answer: Within 4 hours if dose rate exceeds certain limits; within 24 hours for other cases

Per 10 CFR 20.2201, lost or stolen licensed material must be reported within 4 hours (if dose rate thresholds are met) or within 24 hours for quantities above certain levels.

Question 48: Which of the following describes the 'intrinsic efficiency' of a radiation detector?

The total number of counts recorded in the full-energy peak.
The ability of the detector to resolve two closely spaced energy peaks.
The ratio of pulses produced to the number of particles striking the detector. (Correct answer)
The ratio of pulses produced to the total number of particles emitted by the source.

Correct answer: The ratio of pulses produced to the number of particles striking the detector.

Intrinsic efficiency is defined as the ratio of the number of pulses produced by the detector to the number of radiation quanta (e.g., gamma rays) that are incident on the detector's sensitive volume. It represents the probability that a particle striking the detector will cause a recorded event. [14]

Question 49: Which NCRP report specifically addresses the management and disposition of radioactively contaminated soil?

NCRP Report No. 116
NCRP Report No. 129 (Correct answer)
NCRP Report No. 173
NCRP Report No. 146

Correct answer: NCRP Report No. 129

NCRP Report No. 129 (Recommended Screening Limits for Contaminated Surface Soil, 1999) addresses screening limits and management of radioactively contaminated soil.

Question 50: Greater-Than-Class-C (GTCC) LLW differs from Class C LLW primarily because:

Its radionuclide concentrations exceed Class C limits and require deeper disposal (Correct answer)
It is generated exclusively by medical facilities
It contains only naturally occurring radioactive material
It can be disposed of at any licensed LLW facility

Correct answer: Its radionuclide concentrations exceed Class C limits and require deeper disposal

GTCC waste has radionuclide concentrations exceeding the Class C thresholds in 10 CFR Part 61 and is not acceptable for near-surface disposal; it requires disposal in a geologic repository.

Question 51: In which energy range is Compton scattering the dominant interaction mechanism for photons in soft tissue?

10 keV to 100 keV
Above 10 MeV
Below 10 keV
100 keV to 10 MeV (Correct answer)

Correct answer: 100 keV to 10 MeV

For photons interacting with a low-Z material like soft tissue, the photoelectric effect dominates at low energies. As energy increases, Compton scattering becomes the most probable interaction. Pair production becomes dominant at very high energies (above 10 MeV). The intermediate range, approximately 100 keV to 10 MeV, is where Compton scattering is the primary mechanism of energy deposition.

Question 52: The 'ingestion exposure pathway' EPZ around nuclear power plants extends to approximately what distance?

50 miles (Correct answer)
2 miles
10 miles
100 miles

Correct answer: 50 miles

The ingestion pathway EPZ extends to approximately 50 miles to address contamination of food, water, and agricultural products.

Question 53: What is the primary purpose of waste characterization in radioactive waste management?

To calculate the number of workers needed for handling
To establish the color-coding system for waste containers
To determine the monetary value of the waste
To identify radionuclides and quantities to ensure proper classification and disposal (Correct answer)

Correct answer: To identify radionuclides and quantities to ensure proper classification and disposal

Waste characterization identifies the radionuclide inventory, activity levels, and physical/chemical properties needed to classify waste and select the correct disposal pathway.

Question 54: Which respiratory protection device provides the highest protection factor in a radiological environment?

Full-face air-purifying respirator
Self-contained breathing apparatus (SCBA) (Correct answer)
Half-face air-purifying respirator
Powered air-purifying respirator (PAPR)

Correct answer: Self-contained breathing apparatus (SCBA)

SCBA provides a protection factor of 10,000, the highest available, because it supplies breathing air independent of the surrounding atmosphere.

Question 55: During a personnel contamination event, a worker has detectable skin contamination that cannot be removed after three gentle washing attempts. The next appropriate action is to:

Apply a waterproof bandage over the area and continue work
Notify the RSO and seek medical evaluation for possible skin dose assessment (Correct answer)
Perform a whole-body bioassay to determine internal dose
Use abrasive scrubbing compounds to remove the remaining activity

Correct answer: Notify the RSO and seek medical evaluation for possible skin dose assessment

Persistent skin contamination requires RSO involvement and medical evaluation to assess skin dose and determine whether further decontamination is safe or medically warranted.

Question 56: A worker in a laboratory accidentally spills a liquid radioactive solution on their lab coat and gloved hands. What is the immediate, most critical first step for the worker to take?

Begin surveying the area to define the extent of the spill.
Remove the contaminated lab coat and gloves. (Correct answer)
Immediately notify the Radiation Safety Officer (RSO).
Proceed to the nearest emergency shower.

Correct answer: Remove the contaminated lab coat and gloves.

The most critical first step is to remove the source of the contamination from the person to prevent further exposure and potential skin absorption. Removing the contaminated lab coat and gloves accomplishes this quickly and effectively. Notifying the RSO and surveying the area are essential subsequent steps, but personal dose reduction is the top priority.

Question 57: Under 10 CFR Part 20, what is the annual occupational dose limit for the lens of the eye?

1.5 rem (15 mSv)
15 rem (150 mSv) (Correct answer)
5 rem (50 mSv)
50 rem (500 mSv)

Correct answer: 15 rem (150 mSv)

10 CFR 20.1201 sets the annual occupational dose limit for the lens of the eye at 15 rem (150 mSv).

Question 58: When performing a frisking (contamination survey) of a worker exiting a radiological area, which body region should be surveyed last?

Head and hair
Hands and wrists (Correct answer)
Feet and shoes
Torso and back

Correct answer: Hands and wrists

Hands and wrists are surveyed last because they often have the highest contamination potential and are used throughout the frisking process.

Question 59: A healthcare facility's NRC materials license is about to expire. What must be done to continue using radioactive materials legally?

Obtain written approval from the RSO
Transfer all materials to another licensed facility immediately
Notify the state health department and continue under interim authority
Submit a renewal application before the expiration date (Correct answer)

Correct answer: Submit a renewal application before the expiration date

Licensees must submit a renewal application to the NRC before the license expires to continue operations under the existing license terms during NRC review.

Question 60: A worker's thyroid bioassay reveals an uptake of I-131 that results in a committed dose equivalent of 15 rem. Under 10 CFR 20, what is the occupational limit for thyroid dose?

5 rem per year
50 rem per year (Correct answer)
75 rem per year
15 rem per year

Correct answer: 50 rem per year

The occupational dose limit for the thyroid under 10 CFR 20.1201(a)(2) is 50 rem (0.5 Sv) committed dose equivalent per year.

Question 61: Why is documentation of incidents important?

For decoration
To list names alphabetically
To fill space
To document compliance and responses (Correct answer)

Correct answer: To document compliance and responses

Documentation of incidents, such as radiation spills or overexposures, is vital for demonstrating regulatory compliance and for continuous improvement of safety protocols. It provides a clear record of the event, the corrective actions taken, and the effectiveness of the response, aiding in future prevention and training.

Question 62: What is the purpose of a dosimetry report?

Log keyboard activity
Track radiation dose history (Correct answer)
Record parking spaces
Report lunch hours

Correct answer: Track radiation dose history

A dosimetry report provides a detailed record of an individual's occupational radiation exposure over a specific period. Its purpose is to track cumulative radiation doses, ensure that exposure limits are not exceeded, and maintain compliance with radiation safety regulations for long-term health monitoring.

Question 63: A portable alpha spectrometry system used for plutonium air sampling requires the sample to be:

Contained in a sealed, pressurized chamber
In liquid form for accurate energy measurement
Thin and dry to minimize alpha self-absorption within the sample (Correct answer)
Collected on a lead-backed filter to enhance counting efficiency

Correct answer: Thin and dry to minimize alpha self-absorption within the sample

Alpha particles have very short ranges in matter, so thick or wet samples cause energy loss and self-absorption, degrading spectral resolution and reducing detected count rate.

Question 64: When performing personnel decontamination, which sequence is correct?

Remove PPE rapidly to minimize exposure time, then decontaminate
Resurvey while still in PPE, carefully remove PPE from outside-in, then shower and resurvey (Correct answer)
Apply fixative spray before removing PPE to lock contamination in place
Remove PPE, shower, then resurvey

Correct answer: Resurvey while still in PPE, carefully remove PPE from outside-in, then shower and resurvey

The correct sequence minimizes spread: survey in PPE, carefully doff from cleanest surface outward, then shower and resurvey to confirm decontamination.

Question 65: A radionuclide has a physical half-life of 8 days and a biological half-life of 24 days. Its effective half-life is approximately:

6 days (Correct answer)
16 days
4 days
32 days

Correct answer: 6 days

Effective half-life = (T_p × T_b)/(T_p + T_b) = (8 × 24)/(8 + 24) = 192/32 = 6 days.

Question 66: What trigger level typically initiates a formal internal dosimetry investigation under NRC guidance?

Any detectable activity in a bioassay sample
Intake exceeding 10% of the ALI (Correct answer)
Intake exceeding 1% of the ALI
Any positive urine sample result

Correct answer: Intake exceeding 10% of the ALI

NRC and most internal dosimetry programs initiate formal dose assessment investigations when estimated intake exceeds 10% of the ALI.

Question 67: Which Department of Transportation (DOT) regulation primarily governs the transportation of radioactive materials?

40 CFR Part 262
49 CFR Part 170
49 CFR Part 173 Subpart I (Correct answer)
10 CFR Part 71

Correct answer: 49 CFR Part 173 Subpart I

49 CFR Part 173 Subpart I establishes DOT requirements for packaging, labeling, marking, and placarding of radioactive materials during transportation.

Question 68: Which instrument is MOST appropriate for detecting low-level alpha contamination on surfaces?

Sodium iodide (NaI) scintillation detector
Geiger-Müller tube with thin mica window held directly over the surface (Correct answer)
Pressurized ionization chamber (PIC)
Ion chamber survey meter

Correct answer: Geiger-Müller tube with thin mica window held directly over the surface

Alpha particles have very short range in air, so a thin-window GM tube held close to the surface is most effective for detecting surface alpha contamination.

Question 69: Neutrons are considered indirectly ionizing radiation because they primarily interact with matter by:

Undergoing spontaneous decay into protons and electrons.
Repelling atomic electrons via the Coulomb force.
Transferring energy to atomic nuclei, which then cause ionization. (Correct answer)
Directly stripping electrons from the atoms they pass through.

Correct answer: Transferring energy to atomic nuclei, which then cause ionization.

Neutrons have no electric charge and therefore do not interact with atomic electrons via the Coulomb force. Instead, they interact with the nuclei of atoms through processes like elastic and inelastic scattering, or absorption. These interactions transfer kinetic energy to the nucleus, creating a recoil nucleus (a charged particle) that then causes ionization.

Question 70: Under 10 CFR Part 20, what is the required minimum frequency for calibrating survey instruments used in healthcare radiation safety programs?

Monthly
Every 6 months
Annually (Correct answer)
Every 2 years

Correct answer: Annually

Radiation survey instruments must be calibrated at intervals not exceeding 12 months (annually) and after any repair, per 10 CFR 20.1501 requirements.

Question 71: Which instrument is most appropriate for detecting and measuring low-energy beta contamination such as C-14 or H-3?

Sodium iodide scintillation detector
Geiger-Müller detector
Liquid scintillation counter for H-3; thin-window GM for C-14 (Correct answer)
Ion chamber survey meter

Correct answer: Liquid scintillation counter for H-3; thin-window GM for C-14

H-3 emits very low-energy betas that require liquid scintillation counting, while C-14's betas require a thin-window GM detector because standard detectors cannot detect their low energies.

Question 72: Which nuclear decay mode results in no change in atomic mass number (A) but increases atomic number (Z) by one?

Beta-minus decay (Correct answer)
Neutron emission
Alpha decay
Isomeric transition

Correct answer: Beta-minus decay

Beta-minus decay converts a neutron to a proton (Z increases by 1) while emitting a beta particle and antineutrino; A remains unchanged.

Question 73: What does the acronym 'ALARA' stand for and what principle does it represent?

Authorized Limit And Radiation Allowance — regulatory dose caps
All Levels Are Routinely Assessed — periodic dose auditing
As Low As Reasonably Achievable — minimizing dose using practicable means (Correct answer)
Annual Limit on Radiation Activity — source term control

Correct answer: As Low As Reasonably Achievable — minimizing dose using practicable means

ALARA stands for As Low As Reasonably Achievable and requires reducing radiation exposure using time, distance, and shielding whenever practicable.

Question 74: Which particle size range is considered most hazardous for lung deposition from inhaled radioactive aerosols?

Less than 0.1 micrometers
Greater than 100 micrometers
1–5 micrometers (AMAD) (Correct answer)
Greater than 10 micrometers (AMAD)

Correct answer: 1–5 micrometers (AMAD)

Particles in the 1–5 µm AMAD range penetrate into the pulmonary (alveolar) region of the lung where clearance is slowest and dose is highest.

Question 75: What type of shielding requirement typically applies to rooms where x-ray fluoroscopy is permanently installed in a US hospital?

Shielding designed to achieve doses at or below 5 mSv/week in all areas
Shielding adequate to reduce doses to zero in adjacent areas
Shielding designed to maintain doses below 1 mSv/week for controlled areas and 0.02 mSv/week for uncontrolled areas (Correct answer)
No regulatory shielding requirement; shielding is at the institution's discretion

Correct answer: Shielding designed to maintain doses below 1 mSv/week for controlled areas and 0.02 mSv/week for uncontrolled areas

NCRP Report No. 147 and state/NRC regulations require shielding designs that maintain weekly doses below 1 mSv for controlled areas (radiation workers) and 0.02 mSv for uncontrolled areas (public).

Question 76: Under 10 CFR Part 35, which of the following best describes a 'medical event' (formerly misadministration) in radiation therapy?

Any treatment session that differs by more than 5% from the plan
A failure to complete a full course of prescribed radiation therapy
A dose or dosage that differs from the prescribed by specific thresholds causing or able to cause harm (Correct answer)
Any equipment malfunction during a treatment session

Correct answer: A dose or dosage that differs from the prescribed by specific thresholds causing or able to cause harm

A medical event under 10 CFR 35.3045 involves a dose or dosage that differs from the prescription by defined thresholds (e.g., >20% of total dose) with potential to cause harm.

Question 77: What is the main function of a radiation safety officer?

Direct parking
Clean spills
Change uniforms
Ensure radiation safety compliance (Correct answer)

Correct answer: Ensure radiation safety compliance

The Radiation Safety Officer (RSO) is a key individual responsible for developing, implementing, and overseeing all aspects of the radiation safety program within an organization. Their main function is to ensure compliance with all applicable radiation safety regulations and institutional policies. This role is critical for protecting workers, the public, and the environment from radiation hazards.

Question 78: Which administrative control sets dose limits lower than regulatory limits to ensure workers don't inadvertently exceed legal limits?

Exposure rate factor (ERF)
Dose commitment factor (DCF)
Derived air concentration (DAC)
Administrative control level (ACL) (Correct answer)

Correct answer: Administrative control level (ACL)

Administrative control levels (ACLs) are internal organizational limits set below regulatory limits to provide a safety margin and trigger corrective action before limits are exceeded.

Question 79: Which type of radiation is stopped by paper?

X-rays
Alpha particles (Correct answer)
Gamma rays
Neutrons

Correct answer: Alpha particles

Alpha particles are relatively heavy, positively charged particles consisting of two protons and two neutrons. Due to their large mass and charge, they interact strongly with matter, causing them to lose energy rapidly over a very short distance. Consequently, they can be easily stopped by a thin sheet of paper, the outer layer of skin, or even a few centimeters of air.

Question 80: Which regulation mandates handling of biohazardous waste?

EPA Act
OSHA Bloodborne Pathogens (Correct answer)
FDA Rule 121
HIPAA

Correct answer: OSHA Bloodborne Pathogens

The OSHA Bloodborne Pathogens standard (29 CFR 1910.1030) mandates specific procedures for handling biohazardous waste to protect workers from exposure to blood and other potentially infectious materials. This regulation requires employers to implement exposure control plans, provide personal protective equipment, and ensure proper disposal methods. Its purpose is to minimize occupational transmission of diseases like HIV and hepatitis.

Question 81: Under 10 CFR Part 20, what must a licensee do if a worker's total effective dose equivalent exceeds 5 rem in a year?

Double the worker's shielding requirement
Investigate and report to the NRC within 30 days if required thresholds are met (Correct answer)
Issue a citation to the worker
Immediately terminate the worker's dosimetry program

Correct answer: Investigate and report to the NRC within 30 days if required thresholds are met

Exceeding the annual TEDE limit requires investigation and NRC reporting per 20.2203 if the overexposure meets notification thresholds.

Question 82: In whole-body counting, which detection method is most commonly used to measure gamma-emitting internal contamination in a worker?

NaI(Tl) or HPGe scintillation/semiconductor detector system (Correct answer)
Urinalysis
Blood sampling
Nasal swab

Correct answer: NaI(Tl) or HPGe scintillation/semiconductor detector system

Whole-body counters use large NaI(Tl) scintillators or HPGe detectors to directly measure gamma photons emitted from internal radionuclides.

Question 83: In nuclear fission of U-235, the average number of prompt neutrons released per fission event is approximately:

1.0
0.5
5.0
2.5 (Correct answer)

Correct answer: 2.5

Each thermal fission of U-235 releases an average of approximately 2.43 prompt neutrons (often cited as ~2.5), which is essential for sustaining a chain reaction.

Question 84: A technician is tasked with surveying for neutrons. Which of the following instruments is designed specifically for neutron detection?

A cadmium-lined Geiger-Mueller tube
An air-filled ionization chamber
A zinc sulfide (ZnS) scintillator
A Boron Trifluoride (BF3) proportional counter (Correct answer)

Correct answer: A Boron Trifluoride (BF3) proportional counter

Boron Trifluoride (BF3) proportional counters are commonly used for detecting thermal neutrons. [29] Neutrons, being uncharged, are detected indirectly. In a BF3 tube, a neutron interacts with a Boron-10 nucleus, causing a nuclear reaction that releases an alpha particle and a lithium nucleus. These charged particles then ionize the gas, producing a detectable pulse.

Question 85: The mass attenuation coefficient (μ/ρ) of a compound material can be calculated using:

The simple arithmetic mean of elemental coefficients
Only the coefficient of the highest-Z element present
The geometric mean of elemental mass attenuation coefficients
The mixture rule: sum of weight-fraction-weighted elemental coefficients (Correct answer)

Correct answer: The mixture rule: sum of weight-fraction-weighted elemental coefficients

The mixture rule states that μ/ρ for a compound equals the sum of each element's weight fraction multiplied by its elemental mass attenuation coefficient.

Question 86: A tenth-value layer (TVL) reduces radiation intensity to what fraction of the original?

1/100
1/10 (Correct answer)
1/2
1/5

Correct answer: 1/10

A TVL is the thickness of material that attenuates radiation to one-tenth of its original intensity.

Question 87: Under 10 CFR 20, which of the following correctly identifies when a Radiation Work Permit (RWP) or equivalent authorization is typically required?

Whenever a worker carries a personal dosimeter
When entering a High Radiation Area or performing non-routine work with radioactive material (Correct answer)
Only when external dose rates exceed 5 rem/hr
Only for licensed operators working with sealed sources

Correct answer: When entering a High Radiation Area or performing non-routine work with radioactive material

RWPs are administrative controls used to authorize entry into elevated radiation or contamination areas and to define protective measures for non-routine or higher-hazard tasks.

Question 88: What is the purpose of the 'guard ring' electrode in a parallel-plate ionization chamber?

To increase the electric field strength near the collecting electrode
To accelerate positive ions toward the cathode more efficiently
To eliminate field distortions and collect only ions from the defined volume (Correct answer)
To shield the chamber from external electromagnetic interference

Correct answer: To eliminate field distortions and collect only ions from the defined volume

The guard ring maintains a uniform electric field in the collection region and intercepts edge-effect ions so only ionization from the defined sensitive volume is measured.

Question 89: When performing whole-body counting on a potentially internally contaminated individual, the purpose is to:

Detect and quantify gamma-emitting radionuclides in the body (Correct answer)
Determine lung burden of inhaled alpha-emitting particles
Screen for surface contamination remaining after decontamination
Measure external dose received during the emergency

Correct answer: Detect and quantify gamma-emitting radionuclides in the body

Whole-body counters detect gamma radiation emitted from internally deposited radionuclides to estimate internal contamination levels.

Question 90: In a proportional counter, what is the primary advantage over an ionization chamber?

Simpler circuitry requirements
Gas multiplication amplifying the primary ion signal (Correct answer)
Lower sensitivity to gamma radiation
Ability to operate without applied voltage

Correct answer: Gas multiplication amplifying the primary ion signal

Proportional counters operate in the gas multiplication region where avalanche ionization amplifies the primary signal by factors of 10³–10⁵.

Question 91: A radiation worker needs to perform a task in a high radiation area with a dose rate of 150 mrem/hr. The administrative dose limit for this task is 100 mrem. What is the maximum stay time permitted for the worker to complete the task without exceeding the administrative limit?

40 minutes (Correct answer)
60 minutes
30 minutes
20 minutes

Correct answer: 40 minutes

Stay time is calculated by dividing the allowed dose by the dose rate. In this case, Stay Time = 100 mrem / 150 mrem/hr = 0.667 hours. To convert this to minutes, multiply by 60: 0.667 hours * 60 minutes/hour = 40 minutes.

Question 92: The 'derived air concentration' (DAC) in 10 CFR Part 20 is based on:

Breathing 2400 mL/min for 2000 working hours per year receiving one ALI (Correct answer)
Surface contamination per unit area normalized to air volume
The concentration causing 0.5 rem in one hour
The average concentration in ambient air at the site boundary

Correct answer: Breathing 2400 mL/min for 2000 working hours per year receiving one ALI

The DAC is derived by dividing the ALI by the volume of air breathed in a working year (2.4 L/min × 2000 hr), giving the air concentration that delivers one ALI.

Question 93: The half-value layer (HVL) of a gamma-ray beam is 2 cm of lead. What thickness reduces the intensity to 12.5% of the original?

10 cm
6 cm (Correct answer)
4 cm
8 cm

Correct answer: 6 cm

12.5% = (1/2)³, so three HVLs are needed: 3 × 2 cm = 6 cm of lead.

Question 94: What is the regulatory basis for requiring radiation workers to wear dosimetry under 10 CFR Part 20?

Workers who handle sealed sources exclusively
Workers likely to receive 10% or more of any applicable limit (Correct answer)
Any worker who enters a radiation area
Only workers classified as Category A radiation workers

Correct answer: Workers likely to receive 10% or more of any applicable limit

10 CFR 20.1502 requires monitoring for workers likely to receive 10% or more of any applicable annual dose limit.

Question 95: A thermoluminescent dosimeter (TLD) measures absorbed dose by:

Measuring light emitted when heated crystals release stored energy (Correct answer)
Amplifying ionization current with a photomultiplier tube
Detecting changes in chemical composition of a film emulsion
Counting electrical pulses generated by ionization

Correct answer: Measuring light emitted when heated crystals release stored energy

TLDs store energy from radiation in crystal lattice traps; when heated, electrons return to ground state and emit light proportional to the absorbed dose.

Question 96: Which instrument is most appropriate for detecting low-level tritium (H-3) air contamination?

Geiger-Mueller detector
Ionization chamber air monitor
Liquid scintillation counter after air sample collection (Correct answer)
Sodium iodide scintillation detector

Correct answer: Liquid scintillation counter after air sample collection

Tritium's very low-energy beta (18.6 keV max) cannot be detected directly in air; air samples are collected and analyzed by liquid scintillation counting.

Question 97: Which 10 CFR Part 20 section governs the concentration limits for releasing radioactive effluents into sanitary sewerage systems from hospital nuclear medicine departments?

10 CFR 20.1301
10 CFR 20.1501
10 CFR 20.2003 (Correct answer)
10 CFR 20.1801

Correct answer: 10 CFR 20.2003

10 CFR 20.2003 establishes the conditions and concentration limits under which licensed radioactive material may be released into sanitary sewerage systems.

Question 98: Under ALARA, engineered controls are preferred over which type of control?

Neither A nor B
Administrative controls
Personal protective equipment
Both A and B (Correct answer)

Correct answer: Both A and B

The hierarchy of controls places engineering controls above both administrative controls and PPE in the ALARA framework.

Question 99: What is the proper sequence for emergency responders donning Level C personal protective equipment for radiological response?

Coveralls → gloves → boot covers → half-face respirator → tape seams (Correct answer)
Boot covers → coveralls → half-face respirator → gloves → tape seams
Half-face respirator → coveralls → gloves → boot covers → tape seams
Tape seams → coveralls → boot covers → gloves → half-face respirator

Correct answer: Coveralls → gloves → boot covers → half-face respirator → tape seams

Donning sequence proceeds from body suit to extremity protection to respiratory protection, then sealing — ensuring no gaps are created after sealing.

Question 100: When must personnel dosimetry be worn?

While in radiological areas (Correct answer)
When it's cold
Only in daylight
During lunch

Correct answer: While in radiological areas

Personnel dosimetry must be worn by individuals whenever they are working in or entering radiological areas where there is a potential for exposure to ionizing radiation. This ensures that all occupational doses are accurately monitored and recorded, providing a continuous record of exposure. This practice is crucial for compliance with safety regulations and protecting worker health.

Question 101: The operating principle of a thermoluminescent dosimeter (TLD) is based on which of the following phenomena?

Creation of electron-hole pairs in a semiconductor
Darkening of a photographic emulsion
Gas ionization and multiplication
Emission of light proportional to deposited energy upon heating (Correct answer)

Correct answer: Emission of light proportional to deposited energy upon heating

Thermoluminescent dosimeters (TLDs) work by trapping electrons in an excited state within a crystal lattice when exposed to ionizing radiation. When the crystal is heated, these electrons return to their ground state, releasing the stored energy as visible light. The amount of light emitted is proportional to the radiation dose received. [3, 25, 35]

Question 102: Upon receiving a package of radioactive material, what is the initial action a radiation protection technician should perform?

Visually inspect the package for any signs of damage. (Correct answer)
Store the package in a lead-lined cabinet.
Log the package into the inventory system.
Immediately open the package to verify the contents.

Correct answer: Visually inspect the package for any signs of damage.

Standard procedures for receiving radioactive material packages require an initial visual inspection for any signs of damage, such as crushing or wetness. If damage is observed, it could indicate a potential leak or loss of containment, requiring immediate further action like contamination surveys and notification of the RSO.

Question 103: Which regulation governs the safe handling and disposal of radioactive waste generated by nuclear medicine departments in US hospitals?

DOT 49 CFR Part 173
OSHA 29 CFR 1910.120
EPA 40 CFR Part 61
NRC 10 CFR Part 20 Subpart K (Correct answer)

Correct answer: NRC 10 CFR Part 20 Subpart K

10 CFR Part 20 Subpart K establishes NRC requirements for the disposal of licensed radioactive material, including waste generated in nuclear medicine.

Question 104: A radioactive waste shipment requires a 'Type B' package when:

The dose rate at the package surface exceeds 200 mrem/hr
The activity exceeds Type A quantity limits for the specific radionuclide (Correct answer)
The waste is classified as Class C LLW
The waste volume exceeds 55 gallons

Correct answer: The activity exceeds Type A quantity limits for the specific radionuclide

Type B packaging is required when the radioactive material content exceeds the Type A quantity limits specified in 49 CFR 173.431, ensuring containment under accident conditions.

Question 105: Internal conversion (IC) electrons are emitted with energies equal to:

The sum of the gamma-ray energy and the binding energy
The gamma-ray energy minus the electron's atomic binding energy (Correct answer)
Half the gamma-ray energy
The full gamma-ray energy

Correct answer: The gamma-ray energy minus the electron's atomic binding energy

In internal conversion, the nuclear excitation energy is transferred directly to an orbital electron; the electron is ejected with energy equal to the gamma-ray energy minus its atomic binding energy.

Question 106: In a contamination control zone, what is the function of a 'step-off pad'?

Measure the dose rate at floor level in real time
Provide a clean standing surface to don protective clothing
Collect foot contamination as personnel exit the contaminated zone before stepping into clean areas (Correct answer)
Absorb liquid spills at the zone boundary

Correct answer: Collect foot contamination as personnel exit the contaminated zone before stepping into clean areas

Step-off pads are placed at zone exits to capture and detect contamination on shoe covers before personnel move into clean areas.

Question 107: During a radiological emergency, which criterion is used to trigger sheltering-in-place as a protective action?

Projected dose to the thyroid exceeds 50 mSv (Correct answer)
Projected dose exceeds the general public annual limit of 1 mSv
Air concentration of radioiodine exceeds DAC by a factor of 10
Ambient dose rate exceeds 1 mSv/hr at the site boundary

Correct answer: Projected dose to the thyroid exceeds 50 mSv

EPA Protective Action Guides use a projected thyroid dose of 50 mSv as a key threshold for recommending sheltering.

Question 108: Which regulation governs occupational radiation exposure?

21 CFR Part 100
40 CFR Part 61 (Correct answer)
29 CFR Part 1910
10 CFR Part 20

Correct answer: 40 CFR Part 61

While 10 CFR Part 20 is the primary regulation for occupational dose limits for NRC licensees, 40 CFR Part 61, 'National Emission Standards for Hazardous Air Pollutants,' also governs radiation exposure. It sets limits for radionuclide emissions from certain facilities, which indirectly impacts and governs occupational exposure for workers at those sites, especially concerning airborne radioactive materials.

Question 109: What is the NRC's requirement for 'declared pregnant workers' in terms of fetal dose monitoring?

No additional monitoring is required beyond standard whole-body dosimetry
The employer must obtain a written waiver from the worker's obstetrician
A separate deep-dose badge worn at the abdomen is required to estimate fetal dose (Correct answer)
The worker must undergo monthly blood counts to detect radiation effects

Correct answer: A separate deep-dose badge worn at the abdomen is required to estimate fetal dose

Facilities typically issue a second dosimeter to be worn at the abdomen to estimate fetal dose throughout the declared pregnancy in compliance with 10 CFR 20.1208.

Question 110: Which NRC form is used by a receiving licensee to acknowledge transfer of radioactive material between NRC licensees?

NRC Form 374
NRC Form 313
NRC Form 3
NRC Form 540/541 (Correct answer)

Correct answer: NRC Form 540/541

NRC Form 540 (and 541 for consolidated manifests) is the Uniform Low-Level Radioactive Waste Manifest used to document and acknowledge transfers of radioactive material.

Question 111: What is the purpose of a Radiological Work Permit (RWP) or Radiation Work Permit?

To certify that a worker has completed radiation worker training
To record personnel dosimetry readings at the end of a job
To authorize the release of radioactive material to unrestricted areas
To document the radiological conditions, required protective measures, and dose estimates before workers enter a radiological area (Correct answer)

Correct answer: To document the radiological conditions, required protective measures, and dose estimates before workers enter a radiological area

An RWP documents expected radiological conditions, required PPE, dose estimates, and controls that workers must follow before and during work in a radiological area.

Question 112: What is the best method to reduce external radiation exposure?

Wear sunglasses
Increase time near source
Use minimal shielding
Maximize distance and shielding (Correct answer)

Correct answer: Maximize distance and shielding

The three primary methods for reducing external radiation exposure are time, distance, and shielding. Maximizing distance from a radiation source significantly reduces exposure due to the inverse square law, while appropriate shielding materials (like lead or concrete) absorb radiation. Combining these two methods provides the most effective protection against external radiation.

Question 113: A pregnant radiation worker declares her pregnancy to her employer. Under 10 CFR 20.1208, what is the dose limit for the embryo/fetus for the entire gestation period?

5 mSv (Correct answer)
0.5 mSv
50 mSv
1 mSv

Correct answer: 5 mSv

10 CFR 20.1208 limits the dose equivalent to the embryo/fetus to 5 mSv (0.5 rem) during the entire gestation period once pregnancy is declared.

Question 114: When establishing a 'buffer zone' (also called a contamination reduction zone) around a radiological work area, its primary function is to:

House dosimetry storage and radiological instruments for the job
Provide shielding from direct radiation exposure to the public
Satisfy NRC posting requirements for High Radiation Areas
Serve as a transition area where workers can remove and check protective clothing before entering the clean area (Correct answer)

Correct answer: Serve as a transition area where workers can remove and check protective clothing before entering the clean area

The buffer zone is a transition space where workers doff anti-C clothing, perform frisker checks, and prevent contamination from being tracked into unrestricted areas.

Question 115: What is the ultimate fate of an alpha particle after it has lost all its kinetic energy by interacting with matter?

It undergoes annihilation with an electron.
It captures two electrons and becomes a neutral helium atom. (Correct answer)
It splits into two protons and two neutrons.
It remains as a doubly charged ion embedded in the material.

Correct answer: It captures two electrons and becomes a neutral helium atom.

An alpha particle is a helium nucleus (two protons, two neutrons). Once it has slowed down sufficiently by ionizing the surrounding atoms, its positive charge will attract and capture two free electrons from the environment, turning it into a stable, neutral helium atom.

Question 116: What principle requires radiation protection programs to keep doses as low as reasonably achievable, considering economic and social factors?

ALARA (Correct answer)
CEDE
ICRP
TEDE

Correct answer: ALARA

ALARA (As Low As Reasonably Achievable) is the radiation protection principle requiring dose minimization beyond just meeting regulatory limits.

Question 117: An atom undergoes electron capture. What is emitted as a direct result of the orbital electron vacancy created?

A positron and a neutrino
A neutrino only
A beta particle
Characteristic X-rays or Auger electrons (Correct answer)

Correct answer: Characteristic X-rays or Auger electrons

Electron capture creates a vacancy in an inner electron shell; this vacancy is filled by outer-shell electrons, releasing characteristic X-rays or Auger electrons.

Question 118: When bioassay results indicate a worker may have exceeded 10% of the Annual Limit on Intake (ALI), what action is required under 10 CFR 20?

Investigate and assess the intake (Correct answer)
No action needed unless 50% ALI is exceeded
Notify the NRC within 4 hours
Immediately remove the worker from all radiation areas

Correct answer: Investigate and assess the intake

10 CFR 20.2104 requires licensees to assess intakes and resulting committed effective dose equivalent when intake is suspected to exceed 10% of the ALI.

Question 119: According to 10 CFR 20, what is the annual occupational dose limit for the lens of the eye for an adult radiation worker?

15 rem (0.15 Sv) (Correct answer)
50 rem (0.5 Sv)
1.5 rem (0.015 Sv)
5 rem (0.05 Sv)

Correct answer: 15 rem (0.15 Sv)

10 CFR 20.1201 specifies the annual occupational dose limits for adults. The annual limit to the lens of the eye, or Lens Dose Equivalent (LDE), is 15 rems (0.15 Sv).

Question 120: What is the purpose of using a control dosimeter (control badge) in a personnel dosimetry program?

To establish background radiation levels and detect processing artifacts (Correct answer)
To measure the dose at the highest exposure location
To measure neutron dose separately from gamma dose
To calibrate survey instruments

Correct answer: To establish background radiation levels and detect processing artifacts

Control dosimeters are kept in an unoccupied, low-radiation area to account for background and any processing-related response so it can be subtracted from worker readings.

Question 121: The concept of 'controlled area' vs. 'uncontrolled area' in a hospital radiation facility primarily affects which regulatory requirement?

The applicable dose limits and shielding design goals for those spaces (Correct answer)
The frequency of equipment maintenance inspections
The type of radiation detection equipment that must be used
Whether staff in those areas must be licensed by the NRC

Correct answer: The applicable dose limits and shielding design goals for those spaces

Controlled areas are occupied by radiation workers with dose limits of 50 mSv/year; uncontrolled areas are occupied by the public with a limit of 1 mSv/year, directly driving shielding design.

Question 122: A technician measures a dose rate of 400 mR/hr at a distance of 2 feet from a point source. If the technician moves to a distance of 8 feet from the source, what will the new dose rate be, according to the inverse square law?

25 mR/hr (Correct answer)
50 mR/hr
100 mR/hr
12.5 mR/hr

Correct answer: 25 mR/hr

The inverse square law states that radiation intensity is inversely proportional to the square of the distance from the source (I₁d₁² = I₂d₂²). The distance increased by a factor of 4 (from 2 ft to 8 ft). Therefore, the dose rate will decrease by a factor of 4², which is 16. The new dose rate is 400 mR/hr / 16 = 25 mR/hr.

Question 123: What is required before using any new medical equipment?

Warranty registration
Price approval
Acceptance testing (Correct answer)
Room assignment

Correct answer: Acceptance testing

Acceptance testing is a crucial step before any new medical equipment is put into clinical use. This process verifies that the device functions correctly, meets manufacturer specifications, and complies with all relevant safety standards. It ensures the equipment is safe and ready for patient care, identifying any potential issues before they can impact patient outcomes.

Question 124: In the context of radiological protection, 'deterministic effects' differ from stochastic effects because they:

Have a threshold dose and increase in severity with dose above the threshold (Correct answer)
Are caused exclusively by low-LET radiation
Only result from internal contamination
Have no threshold and increase in probability with dose

Correct answer: Have a threshold dose and increase in severity with dose above the threshold

Deterministic effects (e.g., cataracts, radiation burns) have a threshold below which they do not occur and increase in severity as dose exceeds the threshold.

Question 125: The range of alpha particles in tissue is approximately:

Several centimeters
A few tens of micrometers to ~100 μm (Correct answer)
Several meters
Less than 1 nanometer

Correct answer: A few tens of micrometers to ~100 μm

Alpha particles (4–8 MeV) have very short ranges in tissue, typically a few tens to about 100 micrometers, due to their large charge and mass causing dense ionization.

Question 126: A 'Notice to Workers' (NRC Form 3) must be posted in a location where it is:

Displayed only during inspections
Accessible to all workers during normal working hours (Correct answer)
Visible only to supervisors
Kept in the health physics office for reference

Correct answer: Accessible to all workers during normal working hours

10 CFR 19.11 requires NRC Form 3 to be posted conspicuously where workers can see it during working hours.

Question 127: When using a multi-channel analyzer (MCA) for gamma spectroscopy, the gain setting determines:

The minimum count time required for statistically valid results
The electronic threshold below which no pulses are recorded
The relationship between pulse amplitude and channel number, setting the energy range displayed (Correct answer)
The high voltage applied to the photomultiplier tube

Correct answer: The relationship between pulse amplitude and channel number, setting the energy range displayed

MCA gain maps pulse amplitudes (proportional to photon energy) onto the channel number scale, so changing the gain adjusts the energy range and resolution of the displayed spectrum.

Question 128: A technician is preparing to dispose of radioactive waste via decay-in-storage (DIS). According to NRC guidance, what is the maximum permissible half-life for a radionuclide to be eligible for this disposal method?

30 days
90 days
60 days
120 days (Correct answer)

Correct answer: 120 days

The U.S. Nuclear Regulatory Commission (NRC) has determined that low-level radioactive waste with a half-life of 120 days or less is suitable for decay-in-storage. After a sufficient decay period (typically 10 half-lives), the waste can be disposed of as ordinary trash once surveys confirm it is indistinguishable from background radiation.

Question 129: What does the term 'dose conversion factor' (DCF) represent in internal dosimetry?

A factor converting rem to Sievert
The ratio of lung dose to whole-body dose
The committed effective dose per unit activity intake (Sv/Bq or rem/µCi) (Correct answer)
A shielding correction for geometry

Correct answer: The committed effective dose per unit activity intake (Sv/Bq or rem/µCi)

A DCF converts a measured or estimated intake quantity directly into a committed effective dose, typically expressed as Sv/Bq or rem/µCi.

Question 130: A high radiation area (HRA) is defined under 10 CFR 20 as an area where radiation levels could result in a dose equivalent exceeding what value in one hour at 30 cm from the source?

5 mrem (0.05 mSv)
1000 mrem (10 mSv)
500 mrem (5 mSv)
100 mrem (1 mSv) (Correct answer)

Correct answer: 100 mrem (1 mSv)

Per 10 CFR 20.1003, a high radiation area means radiation levels that could result in an individual receiving a dose equivalent in excess of 100 mrem in one hour at 30 cm.

Question 131: Which statement best describes the response of an ionization chamber survey meter in a pulsed radiation field (such as near an accelerator)?

It is unaffected because ionization chambers have no dead time
It accurately measures the average dose rate regardless of pulse characteristics
It always under-reads because pulses saturate the fill gas
It may over-respond due to ion collection efficiency losses at high instantaneous dose rates (Correct answer)

Correct answer: It may over-respond due to ion collection efficiency losses at high instantaneous dose rates

High instantaneous dose rates in pulsed fields can cause ion recombination before collection, reducing ion collection efficiency and causing the meter to over- or under-respond depending on design.

Question 132: A nuclear medicine technologist administers a diagnostic radiopharmaceutical to the wrong patient. Under 10 CFR 35.3045, this is reportable if the administered dosage differs from the prescribed dosage by more than:

50% of the prescribed dosage
5% of the prescribed dosage
10% of the prescribed dosage
20% of the prescribed dosage (Correct answer)

Correct answer: 20% of the prescribed dosage

A medical event in diagnostic nuclear medicine is triggered when the administered dosage differs from the prescribed dosage by more than 20% per 10 CFR 35.3045 criteria.

Question 133: During mass decontamination of ambulatory victims, which body areas should receive priority attention due to highest contamination retention?

Chest and abdomen as the largest surface area
Forearms and shins due to exposure surface area
Hair, face, hands, and skin folds where contamination accumulates (Correct answer)
Back and buttocks due to postural exposure

Correct answer: Hair, face, hands, and skin folds where contamination accumulates

Hair, facial features, and skin folds retain contamination most effectively and pose the highest risk of internal uptake if not prioritized.

Question 134: The 'negligible individual dose' (NID) defined by NCRP Report No. 116 is:

0.01 mSv/year (Correct answer)
1 mSv/year
0.1 mSv/year
0.001 mSv/year

Correct answer: 0.01 mSv/year

NCRP Report No. 116 defines the negligible individual dose as 0.01 mSv/year (1 mrem/year), below which individual protective actions are not warranted.

Question 135: A radiation worker is planning a task in a high radiation area. Which of the following principles is most critical for minimizing their radiation dose?

Contamination control
Stochastic effect prevention
Bioassay monitoring
ALARA (As Low As Reasonably Achievable) (Correct answer)

Correct answer: ALARA (As Low As Reasonably Achievable)

ALARA is a fundamental principle of radiation protection that requires every reasonable effort to be made to keep radiation exposures as far below the dose limits as practical. This is achieved by optimizing protection through time, distance, and shielding, which is especially critical in high radiation areas.

Question 136: When a licensee discovers that an individual received a dose exceeding an occupational limit, the NRC must be notified no later than:

Immediately by phone
Within 30 days in writing only
Within 24 hours by phone, followed by written report within 30 days (Correct answer)
Within 4 hours

Correct answer: Within 24 hours by phone, followed by written report within 30 days

10 CFR 20.2202 requires immediate telephone notification within 24 hours and a written report within 30 days for doses exceeding occupational limits.

Question 137: What action is required when a radiation therapy misadministration results in a dose that differs from the prescribed dose by more than 20% of the total prescribed dose?

File a report only if the patient experiences an adverse health effect
Report to the NRC and notify the referring physician and patient (Correct answer)
Document internally and review at the next RSC meeting
Suspend radiation therapy services pending internal investigation

Correct answer: Report to the NRC and notify the referring physician and patient

Under 10 CFR 35.3045, medical events (misadministrations) meeting dose threshold criteria must be reported to the NRC within 15 days, and the referring physician and patient must be notified.

Question 138: Under Joint Commission standards, when a healthcare facility identifies a radiation safety near-miss event, what is the expected organizational response?

Suspend radiation services until the next accreditation survey
File a voluntary report with the NRC and move on
Conduct a proactive risk assessment and implement corrective actions to prevent recurrence (Correct answer)
Report the event only if a patient's dose exceeded the prescribed amount

Correct answer: Conduct a proactive risk assessment and implement corrective actions to prevent recurrence

The Joint Commission expects healthcare organizations to analyze near-miss events using proactive risk assessment methods (such as FMEA) and implement corrective actions to prevent future occurrences.

Question 139: During a routine survey, a worker is found to have a small spot of removable radioactive contamination on their forearm. What is the most appropriate initial action?

Immediately apply duct tape to the spot to lift the contamination.
Report directly to an off-site medical facility for evaluation.
Scrub the area vigorously with a stiff brush and industrial solvent.
Gently wash the affected area with mild soap and lukewarm water. (Correct answer)

Correct answer: Gently wash the affected area with mild soap and lukewarm water.

Standard procedure for personnel decontamination is to begin with the least aggressive method first. Gentle washing with mild soap and lukewarm water is effective at removing loose contamination without abrading or damaging the skin, which could lead to an intake or prevent further, more aggressive decontamination if needed.

Question 140: The concept of 'committed effective dose equivalent' (CEDE) accounts for radiation dose from:

Internal radionuclide intake integrated over 50 years (Correct answer)
Neutron activation products
External gamma exposure only
Skin contamination within 24 hours

Correct answer: Internal radionuclide intake integrated over 50 years

CEDE is the effective dose equivalent from internally deposited radionuclides, integrated over a 50-year period following intake.

Question 141: In a nuclear power plant emergency, what does Emergency Action Level (EAL) classification 'Site Area Emergency' specifically indicate?

An actual or potential substantial degradation of safety functions with potential for offsite radiological dose (Correct answer)
Minor equipment malfunctions with no threat to safety systems
Loss of offsite power requiring immediate evacuation
A general emergency with imminent radiological threat to public health

Correct answer: An actual or potential substantial degradation of safety functions with potential for offsite radiological dose

Site Area Emergency indicates substantial safety function degradation with potential for, but not imminent, significant offsite dose.

Question 142: Under what condition must personnel performing entry into a high contamination area use a supplied-air respirator (SAR) rather than an air-purifying respirator (APR)?

When any alpha-emitting nuclide is present
When the oxygen concentration is below 19.5% or airborne concentrations would exceed APR protection limits (Correct answer)
When airborne activity exceeds 10 DAC
When the work task duration exceeds 4 hours

Correct answer: When the oxygen concentration is below 19.5% or airborne concentrations would exceed APR protection limits

SARs are required in oxygen-deficient atmospheres (below 19.5% O₂) or when airborne concentrations are too high for an APR's assigned protection factor to adequately limit intake.

Question 143: The ALARA principle as applied to radioactive material control requires that exposures be reduced:

Below the 5 rem/year occupational limit by any means available regardless of cost
To natural background levels before material can be released
To zero activity whenever technically possible
To levels as low as reasonably achievable considering economic and social factors (Correct answer)

Correct answer: To levels as low as reasonably achievable considering economic and social factors

ALARA mandates optimization: dose reductions are pursued as long as the benefit of further reduction is proportionate to the effort and cost required.

Question 144: In the context of the Joint Commission accreditation standards for radiation safety, what does the term 'sentinel event' most commonly refer to?

Any unplanned radiation exposure above background levels
An exposure that exceeds occupational dose limits
A regulatory inspection finding of immediate concern
An unexpected occurrence involving death or serious physical harm to a patient (Correct answer)

Correct answer: An unexpected occurrence involving death or serious physical harm to a patient

A sentinel event is defined by The Joint Commission as an unexpected occurrence involving death or serious physical harm, including those caused by radiation misadministration.

Question 145: What is the NRC's occupational dose limit for the lens of the eye per year?

50 mSv
500 mSv
150 mSv (Correct answer)
15 mSv

Correct answer: 150 mSv

The NRC sets the annual occupational dose limit for the lens of the eye at 150 mSv (15 rem) per 10 CFR 20.1201.

Question 146: A survey meter with a pancake probe is particularly useful for:

Detecting low-energy beta and alpha contamination on surfaces (Correct answer)
Performing gamma spectroscopy in the field
Measuring dose rates inside reactor vessels
Measuring high-energy neutron fields

Correct answer: Detecting low-energy beta and alpha contamination on surfaces

The thin window on a pancake GM probe allows low-energy beta particles and alpha particles to enter the detector, making it ideal for surface contamination surveys.

Question 147: The Annual Limit on Intake (ALI) for a radionuclide is defined as the intake that would result in a committed effective dose equivalent of:

15 rem (0.15 Sv)
1 rem (0.01 Sv)
5 rem (0.05 Sv) (Correct answer)
50 rem (0.5 Sv)

Correct answer: 5 rem (0.05 Sv)

The ALI is the intake of a radionuclide in a year that would result in a committed effective dose equivalent of 5 rem (0.05 Sv), the annual occupational limit.

Question 148: What is the definition of 'mixed waste' in radioactive waste management?

Waste that is both radioactive and hazardous under RCRA (Correct answer)
Waste from multiple nuclear facilities combined
Waste containing both alpha and beta emitters
Waste containing transuranic and low-level components

Correct answer: Waste that is both radioactive and hazardous under RCRA

Mixed waste contains both radioactive material regulated under the Atomic Energy Act and hazardous waste regulated under the Resource Conservation and Recovery Act (RCRA).

Question 149: The concept of 'buildup factor' in gamma-ray shielding accounts for:

Attenuation of the primary beam only
Energy buildup due to electron cascade in the shield
Secondary scattered photons that add to the transmitted dose (Correct answer)
Activation of shielding material by gamma rays

Correct answer: Secondary scattered photons that add to the transmitted dose

The buildup factor (B) accounts for scattered and secondary photons that contribute to dose beyond what the uncollided (primary) beam attenuation predicts.

Question 150: Which radiation weighting factor (wR) is assigned to alpha particles under ICRP 103?

20 (Correct answer)
5
1
10

Correct answer: 20

ICRP Publication 103 assigns a radiation weighting factor of 20 to alpha particles due to their high linear energy transfer (LET).

Question 151: Which of the following photon interactions with matter is characterized by the complete absorption of the incident photon and the ejection of an orbital electron?

Photoelectric Effect (Correct answer)
Rayleigh Scattering
Pair Production
Compton Scattering

Correct answer: Photoelectric Effect

The photoelectric effect is an interaction where an incident photon transfers all of its energy to an orbital electron, which is then ejected from the atom. This process is dominant at lower photon energies and in materials with high atomic numbers (Z).

National Registry of Radiation Protection Technicians (NRRPT) Exam

The NRRPT exam certifies the competency of radiation protection technicians in various aspects of radiation safety and measurement.

150

Questions

240 min

Time Limit

70%

To Pass

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