NRRPT Decontamination & Exposure Prevention 4 — Questions and Answers
Question 1: A High Radiation Area (HRA) requires what type of access control per NRC regulations?
- Posted signs only; no additional controls needed
- Locked or continuously attended control so that no individual is able to enter without being aware of the radiation hazard (Correct answer)
- Self-reading dosimeters issued at the boundary
- Remote monitoring cameras but no physical barrier
Correct answer: Locked or continuously attended control so that no individual is able to enter without being aware of the radiation hazard
HRAs must be locked or continuously attended to prevent inadvertent entry, ensuring workers are aware of the hazard before entering.
Question 2: Which of the following radionuclides poses the greatest internal hazard from inhalation due to its alpha emission and long lung retention?
- Cs-137
- Pu-239 (Correct answer)
- Co-60
- H-3 (Tritium)
Correct answer: Pu-239
Pu-239 is an alpha emitter that, when inhaled, deposits in the lung and lymph nodes where it delivers high LET dose over a long retention period.
Question 3: What is the purpose of a Radiological Work Permit (RWP) or Radiation Work Permit?
- To authorize the release of radioactive material to unrestricted areas
- To document the radiological conditions, required protective measures, and dose estimates before workers enter a radiological area (Correct answer)
- To record personnel dosimetry readings at the end of a job
- To certify that a worker has completed radiation worker training
Correct answer: To document the radiological conditions, required protective measures, and dose estimates before workers enter a radiological area
An RWP documents expected radiological conditions, required PPE, dose estimates, and controls that workers must follow before and during work in a radiological area.
Question 4: In decontamination operations, why should decontamination always proceed from LEAST contaminated areas to MOST contaminated areas?
- To reduce worker fatigue by starting with easier areas first
- To prevent spreading contamination from highly contaminated areas into cleaner areas during the process (Correct answer)
- To allow instruments to warm up on lower-level sources first
- To comply with NRC posting requirements during the process
Correct answer: To prevent spreading contamination from highly contaminated areas into cleaner areas during the process
Working from least to most contaminated prevents cross-contamination — carrying contamination on tools or clothing from hot areas into cleaner zones.
Question 5: Protective clothing (anti-C) used in radiological work primarily protects against:
- External gamma and neutron radiation penetrating the body
- Contamination of the skin and personal clothing from radioactive particles (Correct answer)
- Radiation burns from high-dose-rate sources
- Inhalation of radioactive gases
Correct answer: Contamination of the skin and personal clothing from radioactive particles
Anti-contamination clothing protects the skin and personal clothing from radioactive particle contamination — it provides no significant shielding against penetrating radiation.
Question 6: What action must be taken when a worker's removable contamination on skin cannot be reduced below release limits after three decontamination attempts?
- Seal the area with waterproof tape and release the worker
- Notify the Radiation Protection Supervisor and consider medical evaluation and further bioassay (Correct answer)
- Issue the worker a higher dose badge and allow release
- Classify the contamination as 'fixed' and log it without further action
Correct answer: Notify the Radiation Protection Supervisor and consider medical evaluation and further bioassay
Persistent skin contamination after multiple attempts requires RP supervisor notification and possible medical evaluation to assess internal uptake and plan further action.
Question 7: Which instrument is MOST appropriate for detecting low-level alpha contamination on surfaces?
- Geiger-Müller tube with thin mica window held directly over the surface (Correct answer)
- Ion chamber survey meter
- Pressurized ionization chamber (PIC)
- Sodium iodide (NaI) scintillation detector
Correct answer: Geiger-Müller tube with thin mica window held directly over the surface
Alpha particles have very short range in air, so a thin-window GM tube held close to the surface is most effective for detecting surface alpha contamination.
NRRPT Decontamination & Exposure Prevention 4
A High Radiation Area (HRA) requires what type of access control per NRC regulations?