NRRPT Contamination and Airborne Control 5 — Questions and Answers
Question 1: A worker receives a bioassay (urine) result showing detectable Cs-137. What is the most appropriate immediate next step?
- Assume the result is from external contamination and repeat in 30 days
- Perform dose assessment to estimate committed effective dose equivalent and determine if an intake occurred (Correct answer)
- Report directly to the NRC without internal dose assessment
- Increase TLD badge sensitivity for subsequent monitoring
Correct answer: Perform dose assessment to estimate committed effective dose equivalent and determine if an intake occurred
A positive bioassay triggers a formal intake assessment to calculate the committed effective dose equivalent (CEDE) and determine if regulatory limits were exceeded.
Question 2: Which surface material is generally the most difficult to effectively decontaminate of radioactive contamination?
- Painted smooth steel
- Polished stainless steel
- Unpainted concrete or porous masonry (Correct answer)
- Glazed ceramic tile
Correct answer: Unpainted concrete or porous masonry
Porous materials like concrete allow radioactive material to penetrate into micro-crevices and pores, making complete removal extremely difficult compared to non-porous surfaces.
Question 3: What is the significance of the 'inhalation class' (F, M, or S) assigned to airborne radioactive materials?
- It describes the filter type required to capture the aerosol
- It indicates the rate of absorption from the lung to blood, affecting dose distribution and biokinetics (Correct answer)
- It classifies the material's chemical toxicity independent of radioactivity
- It defines the minimum air flow required for ventilation control
Correct answer: It indicates the rate of absorption from the lung to blood, affecting dose distribution and biokinetics
ICRP lung absorption classes (Fast, Moderate, Slow) describe how quickly inhaled material transfers from the lung to systemic circulation, which determines dose to lung vs. other organs.
Question 4: Under what condition must personnel performing entry into a high contamination area use a supplied-air respirator (SAR) rather than an air-purifying respirator (APR)?
- When airborne activity exceeds 10 DAC
- When the oxygen concentration is below 19.5% or airborne concentrations would exceed APR protection limits (Correct answer)
- When the work task duration exceeds 4 hours
- When any alpha-emitting nuclide is present
Correct answer: When the oxygen concentration is below 19.5% or airborne concentrations would exceed APR protection limits
SARs are required in oxygen-deficient atmospheres (below 19.5% O₂) or when airborne concentrations are too high for an APR's assigned protection factor to adequately limit intake.
Question 5: During a facility decommissioning project, elevated airborne activity is detected unexpectedly. What is the correct sequence of actions?
- Continue work while notifying the RP supervisor by radio
- Stop work, direct workers to evacuate upwind, activate emergency air monitoring, and notify supervision (Correct answer)
- Don additional respiratory protection and continue operations at reduced pace
- Seal the room from outside and monitor remotely
Correct answer: Stop work, direct workers to evacuate upwind, activate emergency air monitoring, and notify supervision
Unexpected elevated airborne activity requires immediate work stoppage and evacuation to prevent further intake, followed by emergency monitoring and supervisory notification.
Question 6: What is 'contamination fixation' and when is it used?
- A laboratory technique to identify specific radionuclides on a smear sample
- Application of a chemical coating to temporarily immobilize loose surface contamination and reduce re-suspension hazard (Correct answer)
- The process of permanently disposing of contaminated materials in a licensed facility
- Fixing the location of contamination on a facility map for regulatory records
Correct answer: Application of a chemical coating to temporarily immobilize loose surface contamination and reduce re-suspension hazard
Contamination fixation involves applying adhesive coatings or fixatives to bind loose surface contamination in place, reducing airborne hazard during decontamination or demolition activities.
Question 7: What parameter is used to evaluate the efficiency of a ventilation system in an airborne radioactivity control area?
- Room temperature differential between supply and exhaust
- Air changes per hour (ACH) and direction of airflow relative to contamination sources (Correct answer)
- Velocity of supply air at the diffuser only
- CO₂ concentration as a proxy for radioactive gas removal
Correct answer: Air changes per hour (ACH) and direction of airflow relative to contamination sources
Both the number of air changes per hour and the directionality of airflow (from clean to contaminated zones) determine how effectively ventilation dilutes and removes airborne radioactivity.
NRRPT Contamination and Airborne Control 5
A worker receives a bioassay (urine) result showing detectable Cs-137.
What is the most appropriate immediate next step?