NRRPT Radiological Control & Safety Procedures 5 — Questions and Answers
Question 1: What is the correct procedure when a personnel dosimeter (TLD or film badge) is lost or damaged?
- Use a spare dosimeter and note the loss in the daily log
- Reconstruct the dose using available survey records, air sample data, and co-worker dosimetry (Correct answer)
- Assign the maximum allowable dose for the period
- Assign zero dose since there is no record of exposure
Correct answer: Reconstruct the dose using available survey records, air sample data, and co-worker dosimetry
When a dosimeter is lost or damaged, dose must be reconstructed using the best available information such as area surveys, air sampling data, bioassay results, and co-worker doses.
Question 2: Under the NRC's 10 CFR 20 access control requirements, who must be informed of their dose and dose limits?
- Only workers whose annual dose exceeds 100 mrem
- All radiation workers at the start of their employment or upon entering a restricted area (Correct answer)
- Only workers assigned to high radiation areas
- Workers only when requested in writing
Correct answer: All radiation workers at the start of their employment or upon entering a restricted area
10 CFR 20.1902 requires that licensees inform workers of dose limits and make their dose records available prior to starting work in a restricted area.
Question 3: Which of the following best describes the inverse square law as applied to radiation protection?
- Radiation intensity decreases proportionally with distance from the source
- Radiation intensity decreases by half for each half-value layer of shielding
- Radiation intensity decreases with the square of the distance from the source (Correct answer)
- Radiation intensity increases proportionally with atomic number of the source
Correct answer: Radiation intensity decreases with the square of the distance from the source
The inverse square law states that radiation intensity varies inversely with the square of the distance from a point source—doubling distance reduces intensity to one-quarter.
Question 4: A radiological contingency plan should include which of the following elements?
- Only the phone numbers of regulatory agencies to be notified
- Identification of credible accidents, estimated consequences, and pre-planned response actions (Correct answer)
- A complete inventory of all radioactive materials on site
- The annual dose summary for all radiation workers
Correct answer: Identification of credible accidents, estimated consequences, and pre-planned response actions
A radiological contingency plan must identify credible accident scenarios, estimate consequences, and specify pre-planned response actions to protect workers and the public.
Question 5: What is the recommended surveying technique to locate the edge of a contamination boundary accurately?
- Move the detector rapidly across the suspect area in a straight line
- Move the detector slowly (2-3 cm/sec) in overlapping parallel paths at a consistent height (Correct answer)
- Hold the detector stationary at 30 cm intervals and record each reading
- Use only smear samples rather than direct measurement to define the boundary
Correct answer: Move the detector slowly (2-3 cm/sec) in overlapping parallel paths at a consistent height
Slow, overlapping systematic survey passes ensure thorough coverage and allow the instrument's response time to register localized contamination without missing spots.
Question 6: A worker receives an unplanned dose of 1.25 rem during an emergency that was not anticipated in the RWP. Under ALARA principles, what is the most appropriate next step?
- File an NRC incident report immediately since the dose exceeds 1 rem
- Conduct a post-job review to analyze the cause, assess controls, and prevent recurrence (Correct answer)
- Automatically remove the worker from radiation work for the remainder of the year
- Reduce the worker's annual dose limit by the amount already received
Correct answer: Conduct a post-job review to analyze the cause, assess controls, and prevent recurrence
Post-job reviews of unplanned exposures are a key ALARA practice to identify root causes, evaluate the effectiveness of controls, and implement improvements.
Question 7: When using the 'point source' approximation to estimate shielding requirements, which condition invalidates this approximation?
- When the source is more than 1 meter from the shielding material
- When the source dimensions are comparable to or larger than the distance to the point of interest (Correct answer)
- When the photon energy exceeds 1 MeV
- When scatter radiation contributes more than 10% of the total dose rate
Correct answer: When the source dimensions are comparable to or larger than the distance to the point of interest
The point source approximation is only valid when the source is small compared to the distance to the receptor; for distributed sources, more complex geometric calculations are required.
NRRPT Radiological Control & Safety Procedures 5
What is the correct procedure when a personnel dosimeter (TLD or film badge) is lost or damaged?