Radiation Health Physics Exam
Questions with Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
Domain 1 — Measurements and Instrumentation
1. A radiation detector records 4,900 counts during a 10-minute measurement.
What is the average count rate?
A. 49 counts/minute
B. 490 counts/minute
C. 4,900 counts/minute
D. 49,000 counts/minute
Correct Answer: B. 490 counts/minute
Rationale: Count rate is calculated by dividing the total number of recorded counts
by the counting time. Thus, 4,900 counts ÷ 10 minutes = 490 counts/minute.
2. Which detector is generally most appropriate for locating low-level beta and
gamma contamination during a personnel frisk?
A. Neutron rem meter
B. Ionization chamber
C. Alpha spectrometer
D. Geiger-Mueller survey meter with an appropriate probe
Correct Answer: D. Geiger-Mueller survey meter with an appropriate probe
Rationale: A GM instrument can provide sensitive detection of relatively low levels
of beta and gamma radiation and is commonly used for contamination surveys.
The specific probe must be appropriate for the radiation being monitored.
,3. A background count is 100 counts in 5 minutes. A sample produces 600 counts
in 5 minutes. What is the net sample count rate?
A. 20 counts/minute
B. 100 counts/minute
C. 120 counts/minute
D. 140 counts/minute
Correct Answer: B. 100 counts/minute
Rationale: The gross sample count rate is 600 ÷ 5 = 120 counts/minute.
Background is 100 ÷ 5 = 20 counts/minute. Subtracting background gives a net
count rate of 100 counts/minute.
4. Which characteristic is most important when selecting a radiation detector
for measuring a specific radionuclide?
A. Detector response to the radiation energy and type emitted
B. Color of the detector housing
C. Manufacturer's country of origin
D. Battery capacity alone
Correct Answer: A. Detector response to the radiation energy and type emitted
Rationale: Radiation detectors have different sensitivities and efficiencies for
different radiation types and energies. Detector selection therefore must be based
on the radiation field and measurement objective.
5. A contamination survey requires detecting removable radioactive material on
a work surface. Which method is most appropriate?
A. Direct measurement only with a high-range dose-rate meter
B. Measuring room temperature
C. Taking a smear or swipe sample and counting it appropriately
D. Measuring electrical resistance of the surface
,Correct Answer: C. Taking a smear or swipe sample and counting it
appropriately
Rationale: A smear or swipe samples removable contamination from a surface.
The sample can then be counted using an appropriate detector to determine
whether radioactive material is present and estimate its activity.
6. A detector has a counting efficiency of 25%. If the detector records 2,500
counts per minute from a source, what is the corresponding emission rate under
the stated counting geometry?
A. 625 emissions/minute
B. 2,500 emissions/minute
C. 6,250 emissions/minute
D. 10,000 emissions/minute
Correct Answer: D. 10,000 emissions/minute
Rationale: Counting efficiency = observed count rate ÷ emission rate. Therefore,
emission rate = 2,500 ÷ 0.25 = 10,000 emissions/minute.
Domain 2 — Standards and Requirements
7. Which organization is primarily responsible for establishing federal
regulations governing commercial nuclear power reactor operations in the
United States?
A. U.S. Nuclear Regulatory Commission (NRC)
B. Occupational Safety and Health Administration (OSHA)
C. Environmental Protection Agency (EPA)
D. Department of Transportation (DOT)
Correct Answer: A. U.S. Nuclear Regulatory Commission (NRC)
Rationale: The NRC regulates civilian use of nuclear materials and facilities,
including commercial nuclear power reactors. Other federal agencies have
different regulatory responsibilities.
, 8. Which radiation-protection principle emphasizes keeping exposures as low as
reasonably achievable while considering social and economic factors?
A. Justification
B. Optimization
C. Dose reconstruction
D. Source accountability
Correct Answer: B. Optimization
Rationale: Optimization is the radiation-protection principle underlying ALARA. It
seeks to reduce exposures as far as reasonably achievable while considering
relevant technological, economic, and societal factors.
9. A worker receives an external dose and an internal dose during the same
monitoring period. Which quantity is intended to represent the combined
stochastic radiation risk from these exposures?
A. Air kerma
B. Absorbed dose
C. Total effective dose equivalent
D. Exposure rate
Correct Answer: C. Total effective dose equivalent
Rationale: Effective-dose-based quantities account for radiation and tissue
weighting and can be used to combine relevant external and internal exposures
for assessing stochastic radiation risk.
10. Which regulatory area is most directly associated with requirements for
transporting radioactive material between locations?
A. Occupational hearing conservation
B. Food labeling
C. Medical-device manufacturing
D. Hazardous-material transportation requirements
Questions with Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
Domain 1 — Measurements and Instrumentation
1. A radiation detector records 4,900 counts during a 10-minute measurement.
What is the average count rate?
A. 49 counts/minute
B. 490 counts/minute
C. 4,900 counts/minute
D. 49,000 counts/minute
Correct Answer: B. 490 counts/minute
Rationale: Count rate is calculated by dividing the total number of recorded counts
by the counting time. Thus, 4,900 counts ÷ 10 minutes = 490 counts/minute.
2. Which detector is generally most appropriate for locating low-level beta and
gamma contamination during a personnel frisk?
A. Neutron rem meter
B. Ionization chamber
C. Alpha spectrometer
D. Geiger-Mueller survey meter with an appropriate probe
Correct Answer: D. Geiger-Mueller survey meter with an appropriate probe
Rationale: A GM instrument can provide sensitive detection of relatively low levels
of beta and gamma radiation and is commonly used for contamination surveys.
The specific probe must be appropriate for the radiation being monitored.
,3. A background count is 100 counts in 5 minutes. A sample produces 600 counts
in 5 minutes. What is the net sample count rate?
A. 20 counts/minute
B. 100 counts/minute
C. 120 counts/minute
D. 140 counts/minute
Correct Answer: B. 100 counts/minute
Rationale: The gross sample count rate is 600 ÷ 5 = 120 counts/minute.
Background is 100 ÷ 5 = 20 counts/minute. Subtracting background gives a net
count rate of 100 counts/minute.
4. Which characteristic is most important when selecting a radiation detector
for measuring a specific radionuclide?
A. Detector response to the radiation energy and type emitted
B. Color of the detector housing
C. Manufacturer's country of origin
D. Battery capacity alone
Correct Answer: A. Detector response to the radiation energy and type emitted
Rationale: Radiation detectors have different sensitivities and efficiencies for
different radiation types and energies. Detector selection therefore must be based
on the radiation field and measurement objective.
5. A contamination survey requires detecting removable radioactive material on
a work surface. Which method is most appropriate?
A. Direct measurement only with a high-range dose-rate meter
B. Measuring room temperature
C. Taking a smear or swipe sample and counting it appropriately
D. Measuring electrical resistance of the surface
,Correct Answer: C. Taking a smear or swipe sample and counting it
appropriately
Rationale: A smear or swipe samples removable contamination from a surface.
The sample can then be counted using an appropriate detector to determine
whether radioactive material is present and estimate its activity.
6. A detector has a counting efficiency of 25%. If the detector records 2,500
counts per minute from a source, what is the corresponding emission rate under
the stated counting geometry?
A. 625 emissions/minute
B. 2,500 emissions/minute
C. 6,250 emissions/minute
D. 10,000 emissions/minute
Correct Answer: D. 10,000 emissions/minute
Rationale: Counting efficiency = observed count rate ÷ emission rate. Therefore,
emission rate = 2,500 ÷ 0.25 = 10,000 emissions/minute.
Domain 2 — Standards and Requirements
7. Which organization is primarily responsible for establishing federal
regulations governing commercial nuclear power reactor operations in the
United States?
A. U.S. Nuclear Regulatory Commission (NRC)
B. Occupational Safety and Health Administration (OSHA)
C. Environmental Protection Agency (EPA)
D. Department of Transportation (DOT)
Correct Answer: A. U.S. Nuclear Regulatory Commission (NRC)
Rationale: The NRC regulates civilian use of nuclear materials and facilities,
including commercial nuclear power reactors. Other federal agencies have
different regulatory responsibilities.
, 8. Which radiation-protection principle emphasizes keeping exposures as low as
reasonably achievable while considering social and economic factors?
A. Justification
B. Optimization
C. Dose reconstruction
D. Source accountability
Correct Answer: B. Optimization
Rationale: Optimization is the radiation-protection principle underlying ALARA. It
seeks to reduce exposures as far as reasonably achievable while considering
relevant technological, economic, and societal factors.
9. A worker receives an external dose and an internal dose during the same
monitoring period. Which quantity is intended to represent the combined
stochastic radiation risk from these exposures?
A. Air kerma
B. Absorbed dose
C. Total effective dose equivalent
D. Exposure rate
Correct Answer: C. Total effective dose equivalent
Rationale: Effective-dose-based quantities account for radiation and tissue
weighting and can be used to combine relevant external and internal exposures
for assessing stochastic radiation risk.
10. Which regulatory area is most directly associated with requirements for
transporting radioactive material between locations?
A. Occupational hearing conservation
B. Food labeling
C. Medical-device manufacturing
D. Hazardous-material transportation requirements
