NRRPT Decontamination & Exposure Prevention 3 — Questions and Answers
Question 1: Which type of respiratory protection is required when airborne radioactive contamination concentrations are unknown or potentially high?
- A surgical mask rated N95
- A supplied-air respirator (SAR) or self-contained breathing apparatus (SCBA) (Correct answer)
- A half-face air-purifying respirator with HEPA filters
- No respiratory protection is needed if skin dose is low
Correct answer: A supplied-air respirator (SAR) or self-contained breathing apparatus (SCBA)
When airborne concentrations are unknown or potentially high, supplied-air or SCBA equipment provides the highest level of protection against inhalation.
Question 2: A radiological posting reading 'Radiation Area' (per NRC 10 CFR 20) indicates a dose rate of at least:
- 5 mrem/hr at 30 cm
- 5 mrem/hr at any point 30 cm from the source or surface (Correct answer)
- 100 mrem/hr at 1 meter
- 2 mrem/hr at 30 cm
Correct answer: 5 mrem/hr at any point 30 cm from the source or surface
NRC regulations define a Radiation Area as any area where dose rate exceeds 5 mrem/hr (0.05 mSv/hr) at 30 cm from the source or accessible surface.
Question 3: What is the primary hazard associated with ingestion of radioactive contamination compared to external exposure?
- Ingestion always produces a higher effective dose than external exposure for the same activity
- Ingestion results in internal contamination, delivering dose to organs over a prolonged period based on the radionuclide's biological half-life (Correct answer)
- Ingestion only affects the gastrointestinal tract and no other organs
- Ingestion of alpha emitters poses no significant hazard
Correct answer: Ingestion results in internal contamination, delivering dose to organs over a prolonged period based on the radionuclide's biological half-life
Ingested radionuclides become internal contamination, delivering dose to target organs continuously based on both physical and biological half-lives.
Question 4: Double gloving is a common practice in radiological work. What is the key procedural advantage when removing double gloves?
- It reduces neutron dose to the hands by 50%
- The outer glove can be removed first while the inner glove remains clean, preventing hand contamination during removal (Correct answer)
- It allows workers to work in high-dose-rate areas for twice as long
- It provides a second radiation shield equivalent to 0.5 mm lead
Correct answer: The outer glove can be removed first while the inner glove remains clean, preventing hand contamination during removal
Double gloving allows safe removal of the outer contaminated glove while keeping the inner glove clean, reducing the risk of hand contamination during doffing.
Question 5: Which bioassay technique is used to assess internal contamination by measuring radiation emitted directly from the body?
- Urinalysis with gamma spectrometry
- Whole-body counting (in-vivo counting) (Correct answer)
- Nasal swab analysis
- Fecal sample gamma counting
Correct answer: Whole-body counting (in-vivo counting)
Whole-body counting detects gamma-emitting radionuclides inside the body by measuring radiation emanating directly through the body surface.
Question 6: A 'hot spot' found during a decontamination survey refers to:
- An area with elevated ambient temperature from decay heat
- A localized area with significantly higher contamination levels than the surrounding surface (Correct answer)
- Any area above background requiring a posted boundary
- A region where only alpha contamination is present
Correct answer: A localized area with significantly higher contamination levels than the surrounding surface
A hot spot is a localized concentration of contamination significantly higher than the surrounding area, requiring targeted decontamination.
Question 7: When using Time, Distance, and Shielding to reduce dose, which factor provides the fastest dose reduction for a worker already positioned near a source?
- Shielding — adding lead between the worker and source
- Distance — moving away from the source reduces dose rate by the inverse square law (Correct answer)
- Time — spending less total time near the source
- Dosimetry — wearing a TLD to track accumulated dose
Correct answer: Distance — moving away from the source reduces dose rate by the inverse square law
Increasing distance reduces dose rate according to the inverse square law (doubling distance reduces dose rate to one-quarter), often providing the fastest immediate reduction.
NRRPT Decontamination & Exposure Prevention 3
Which type of respiratory protection is required when airborne radioactive contamination concentrations are unknown or potentially high?