NANTeL Radiation Protection and ALARA 2 — Questions and Answers
Question 1: Which of the three ALARA principle controls directly reduces the intensity of radiation reaching a worker?
- Time
- Distance
- Shielding (Correct answer)
- Ventilation
Correct answer: Shielding
Shielding places absorbing material between the source and the worker, directly attenuating radiation intensity.
Question 2: A worker doubles their distance from a point radiation source. By what factor does dose rate change according to the inverse square law?
- Decreases by half
- Decreases by a factor of 4 (Correct answer)
- Decreases by a factor of 8
- Remains the same
Correct answer: Decreases by a factor of 4
The inverse square law states that dose rate is proportional to 1/d², so doubling distance reduces dose rate by a factor of 4.
Question 3: In nuclear facilities, which type of radiation is most effectively shielded by high-density materials such as lead or concrete?
- Alpha particles
- Beta particles
- Gamma rays (Correct answer)
- Neutrons
Correct answer: Gamma rays
Gamma rays are highly penetrating photons that require dense materials like lead or thick concrete for effective shielding.
Question 4: What is the primary purpose of a whole-body count (WBC) performed on nuclear plant workers?
- Measure external dose rate
- Detect internal contamination from radionuclides (Correct answer)
- Calibrate dosimeters
- Determine shielding requirements
Correct answer: Detect internal contamination from radionuclides
A whole-body count uses sensitive gamma detectors to identify and quantify radionuclides that have been internally deposited in the body.
Question 5: Under 10 CFR Part 20, what is the annual occupational dose limit for the whole body?
- 1 rem (10 mSv)
- 5 rem (50 mSv) (Correct answer)
- 15 rem (150 mSv)
- 25 rem (250 mSv)
Correct answer: 5 rem (50 mSv)
10 CFR 20.1201 sets the annual occupational total effective dose equivalent (TEDE) limit at 5 rem (50 mSv).
Question 6: Which personal protective equipment (PPE) is LEAST effective at protecting against gamma radiation exposure?
- Lead apron
- Anti-contamination clothing (anti-C) (Correct answer)
- Lead gloves
- Lead thyroid shield
Correct answer: Anti-contamination clothing (anti-C)
Anti-contamination clothing prevents skin contamination but provides no attenuation against penetrating gamma radiation.
Question 7: What does the term 'controlled area' mean in the context of NRC regulations at a nuclear facility?
- An area where dose rates exceed 100 mrem/hr
- An area where access and occupancy are controlled for radiation protection purposes (Correct answer)
- An area restricted to radiation protection staff only
- An area where only respirators are required
Correct answer: An area where access and occupancy are controlled for radiation protection purposes
A controlled area is defined in 10 CFR 20.1003 as one where access and occupancy are controlled to protect individuals from radiation and radioactive materials.
NANTeL Radiation Protection and ALARA 2
Which of the three ALARA principle controls directly reduces the intensity of radiation reaching a worker?