CMD Radiation Safety & Protection 2 — Questions and Answers
Question 1: What is the annual occupational effective dose limit for radiation workers in the United States?
- 20 mSv
- 50 mSv (Correct answer)
- 100 mSv
- 5 mSv
Correct answer: 50 mSv
The NRC sets the annual occupational effective dose limit at 50 mSv (5 rem) per year for radiation workers.
Question 2: Which radiation quantity accounts for both the absorbed dose and the biological effectiveness of different radiation types?
- Absorbed dose (Gray)
- Equivalent dose (Sievert) (Correct answer)
- Exposure (Roentgen)
- Kerma
Correct answer: Equivalent dose (Sievert)
Equivalent dose in Sieverts equals absorbed dose multiplied by the radiation weighting factor, reflecting biological effectiveness.
Question 3: A dosimetrist is planning a high-dose-rate brachytherapy procedure. What is the minimum recommended shielding material thickness for a dedicated HDR vault with Ir-192?
- 12 inches of lead
- 24 inches of concrete or equivalent (Correct answer)
- 6 inches of concrete
- 3 inches of lead
Correct answer: 24 inches of concrete or equivalent
HDR Ir-192 vaults typically require approximately 24 inches (60 cm) of concrete or equivalent shielding to meet dose rate limits in adjacent areas.
Question 4: Which principle of radiation protection requires that doses be kept as low as reasonably achievable?
- Justification
- ALARA (Correct answer)
- Optimization
- Dose constraint
Correct answer: ALARA
ALARA (As Low As Reasonably Achievable) is the guiding principle requiring radiation doses to be minimized beyond regulatory limits when practical.
Question 5: When using a survey meter to check for contamination after a brachytherapy seed implant procedure, which meter type is most appropriate?
- Cutie pie ionization chamber
- Geiger-Müller detector (Correct answer)
- Thermoluminescent dosimeter
- Film badge
Correct answer: Geiger-Müller detector
A Geiger-Müller detector is the most appropriate survey instrument for contamination checks due to its high sensitivity for detecting small amounts of radioactivity.
Question 6: What is the lens of the eye annual dose equivalent limit for radiation workers per NRC regulations?
- 50 mSv
- 150 mSv (Correct answer)
- 500 mSv
- 15 mSv
Correct answer: 150 mSv
The NRC annual dose equivalent limit for the lens of the eye is 150 mSv (15 rem) for occupational workers.
Question 7: A radiation worker's personal dosimeter reads significantly higher than expected after a month. What is the FIRST action to take?
- Discard the dosimeter and issue a new one
- Investigate the cause before drawing conclusions (Correct answer)
- Immediately restrict the worker from radiation areas
- Report to the NRC within 24 hours
Correct answer: Investigate the cause before drawing conclusions
The first step is always to investigate whether the reading reflects actual exposure, dosimeter malfunction, or inadvertent irradiation before taking further action.
CMD Radiation Safety & Protection 2
What is the annual occupational effective dose limit for radiation workers in the United States?