NRRPT Contamination and Airborne Control 4 — Questions and Answers
Question 1: Which particle size range is considered most hazardous for lung deposition from inhaled radioactive aerosols?
- Greater than 10 micrometers (AMAD)
- 1–5 micrometers (AMAD) (Correct answer)
- Less than 0.1 micrometers
- Greater than 100 micrometers
Correct answer: 1–5 micrometers (AMAD)
Particles in the 1–5 µm AMAD range penetrate into the pulmonary (alveolar) region of the lung where clearance is slowest and dose is highest.
Question 2: A High Efficiency Particulate Air (HEPA) filter is rated to remove what minimum percentage of 0.3-micron particles?
- 95%
- 99.0%
- 99.97% (Correct answer)
- 99.995%
Correct answer: 99.97%
HEPA filters must remove at least 99.97% of particles at the most penetrating particle size of 0.3 µm per standard definitions (DOE/NRC requirements).
Question 3: What is the purpose of conducting a 'low-volume grab sample' for airborne radioactivity?
- Provide long-term integrated exposure data for dose reconstruction
- Obtain a short-duration air sample to characterize airborne concentrations quickly during a specific task (Correct answer)
- Replace the need for a CAM in routine areas
- Sample effluent discharge points at the facility boundary
Correct answer: Obtain a short-duration air sample to characterize airborne concentrations quickly during a specific task
Grab samples collect air over a short period to characterize concentrations during a specific work evolution, providing rapid task-specific data.
Question 4: When using HEPA vacuums to clean up dry radioactive contamination, which practice is critical to prevent re-suspension?
- Use high suction speed to capture particles rapidly
- Keep the vacuum nozzle moving quickly across the surface
- Pre-wet the surface with a fixative or water mist before vacuuming (Correct answer)
- Operate the HEPA vacuum in reverse-flow mode first
Correct answer: Pre-wet the surface with a fixative or water mist before vacuuming
Pre-wetting or applying a fixative binds loose particles to the surface, reducing re-suspension during the vacuuming process.
Question 5: What does a DAC-hour represent in radiation protection practice?
- The product of airborne concentration in DAC units and the time in hours of exposure (Correct answer)
- The time required to reach the ALI at one DAC
- The hourly dose rate in a 1-DAC airborne environment
- The number of hours per day a CAM must be monitored
Correct answer: The product of airborne concentration in DAC units and the time in hours of exposure
A DAC-hour is the product of the airborne concentration (expressed as a fraction of DAC) and the time in hours, used to track cumulative internal dose potential.
Question 6: In a contamination control zone, what is the function of a 'step-off pad'?
- Provide a clean standing surface to don protective clothing
- Collect foot contamination as personnel exit the contaminated zone before stepping into clean areas (Correct answer)
- Measure the dose rate at floor level in real time
- Absorb liquid spills at the zone boundary
Correct answer: Collect foot contamination as personnel exit the contaminated zone before stepping into clean areas
Step-off pads are placed at zone exits to capture and detect contamination on shoe covers before personnel move into clean areas.
Question 7: Which administrative control document formally authorizes work in a radiologically contaminated area and specifies required PPE and air sampling?
- Radiological work permit (RWP) or radiation work permit (Correct answer)
- Radiation survey report
- Dosimetry assignment log
- Area posting placard
Correct answer: Radiological work permit (RWP) or radiation work permit
An RWP (Radiation Work Permit) is the formal authorization document that specifies radiological conditions, required PPE, monitoring requirements, and dose limits for a specific task.
NRRPT Contamination and Airborne Control 4
Which particle size range is considered most hazardous for lung deposition from inhaled radioactive aerosols?