NRRPT Dosimetry and Exposure Control 5 — Questions and Answers
Question 1: A radiation worker is classified as a declared pregnant worker. The NRC dose limit to the embryo/fetus for the entire gestation period is:
- 5 rem total
- 0.5 rem (500 mrem) total (Correct answer)
- 1.5 rem total
- 5 rem per trimester
Correct answer: 0.5 rem (500 mrem) total
10 CFR 20.1208 limits the dose to the embryo/fetus of a declared pregnant worker to 0.5 rem (5 mSv) over the entire gestation period.
Question 2: When using the DAC-hour concept for internal dosimetry, a worker who spends 8 hours in an area at 2 DAC accumulates:
- 2 DAC-hours
- 8 DAC-hours
- 16 DAC-hours (Correct answer)
- 4 DAC-hours
Correct answer: 16 DAC-hours
DAC-hours = DAC multiplier × hours of exposure = 2 DAC × 8 hours = 16 DAC-hours.
Question 3: Optically Stimulated Luminescence (OSL) dosimeters use which material as the detection medium?
- Lithium fluoride (LiF)
- Aluminum oxide (Al2O3:C) (Correct answer)
- Silver halide crystals
- Boron trifluoride (BF3)
Correct answer: Aluminum oxide (Al2O3:C)
OSL dosimeters use carbon-doped aluminum oxide (Al2O3:C) crystals that store radiation energy and release it as light when stimulated by laser.
Question 4: The occupational dose limit for the skin and extremities under 10 CFR 20 is:
- 5 rem/year
- 15 rem/year
- 25 rem/year
- 50 rem/year (Correct answer)
Correct answer: 50 rem/year
10 CFR 20.1201 sets the annual occupational dose limit for the skin and extremities at 50 rem (500 mSv) per year.
Question 5: Which of the following is a limitation of film badge dosimeters compared to TLDs?
- Film badges cannot measure neutron dose
- Film badges fade over time and are affected by heat and humidity (Correct answer)
- Film badges cannot distinguish between different radiation types
- Film badges must be read within 24 hours of use
Correct answer: Film badges fade over time and are affected by heat and humidity
Film badges can fade (lose recorded dose information) when exposed to heat, humidity, or over extended time periods, reducing accuracy for long-wear periods.
Question 6: 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:
- Immediately suspend the worker from all radiation work
- Estimate the intake and calculate the committed effective dose equivalent (Correct answer)
- Notify the NRC within 24 hours
- 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 7: What does the H*(10) quantity represent in radiation protection dosimetry?
- The committed dose equivalent at 10 cm tissue depth
- The ambient dose equivalent at 10 mm depth in the ICRU sphere, used for area monitoring (Correct answer)
- The effective dose from 10 consecutive occupational exposures
- The dose equivalent to 10% of the body surface area
Correct answer: The ambient dose equivalent at 10 mm depth in the ICRU sphere, used for area monitoring
H*(10) is the ambient dose equivalent at a depth of 10 mm in the ICRU sphere, a quantity used in area monitoring instruments to approximate effective dose for penetrating radiation.
NRRPT Dosimetry and Exposure Control 5
A radiation worker is classified as a declared pregnant worker.
The NRC dose limit to the embryo/fetus for the entire gestation period is: