NRRPT Contamination and Airborne Control 3 — Questions and Answers
Question 1: When performing personnel decontamination, which sequence is correct?
- Remove PPE, shower, then resurvey
- Resurvey while still in PPE, carefully remove PPE from outside-in, then shower and resurvey (Correct answer)
- Remove PPE rapidly to minimize exposure time, then decontaminate
- Apply fixative spray before removing PPE to lock contamination in place
Correct answer: Resurvey while still in PPE, carefully remove PPE from outside-in, then shower and resurvey
The correct sequence minimizes spread: survey in PPE, carefully doff from cleanest surface outward, then shower and resurvey to confirm decontamination.
Question 2: What is the primary hazard associated with re-suspension of radioactive surface contamination?
- External dose rate increases dramatically when contamination becomes airborne
- Settled contamination becomes airborne and creates an inhalation hazard (Correct answer)
- Re-suspended material increases shine dose from the floor
- Re-suspension changes the isotope's decay mode
Correct answer: Settled contamination becomes airborne and creates an inhalation hazard
Re-suspension converts fixed surface contamination into an airborne hazard, dramatically increasing the potential for internal contamination via inhalation.
Question 3: Which factor most directly determines the assigned protection factor (APF) of a respirator?
- The type of radioactive isotope being controlled
- The respirator's ability to reduce the wearer's exposure relative to outside concentration (Correct answer)
- The color-coding of the cartridge used
- The duration of the work task
Correct answer: The respirator's ability to reduce the wearer's exposure relative to outside concentration
APF is defined as the maximum ratio of outside to inside concentration that a properly functioning respirator provides to a trained wearer.
Question 4: A radioactive liquid spill occurs on an open bench. What is the FIRST priority action?
- Contact the radiation protection manager
- Limit the spread of contamination by covering the spill with absorbent material (Correct answer)
- Evacuate the entire building
- Begin decontamination immediately using wet methods
Correct answer: Limit the spread of contamination by covering the spill with absorbent material
The immediate priority is containment — preventing the spill from spreading further — before notifications and decontamination begin.
Question 5: For alpha-emitting contamination, why is the smear (wipe) method the preferred survey technique rather than direct GM survey?
- Alpha particles are too energetic and would damage GM tube walls
- Alpha particles have very short range in air and cannot travel from a surface to the detector window (Correct answer)
- GM tubes cannot be calibrated for alpha radiation
- Alpha emitters produce no ionization detectable by GM tubes
Correct answer: Alpha particles have very short range in air and cannot travel from a surface to the detector window
Alpha particles travel only a few centimeters in air, so unless the detector is in direct contact, activity on a surface cannot reach the tube; wipes bring material to a suitable counter.
Question 6: Under 10 CFR 20, what is the derived air concentration (DAC) concept used to calculate?
- The maximum surface contamination allowed in a restricted area
- The airborne concentration of a radionuclide that, if breathed for a working year, would deliver the occupational ALI (Correct answer)
- The shielding thickness required to reduce dose to 1 mSv/y
- The allowable effluent concentration in public waterways
Correct answer: The airborne concentration of a radionuclide that, if breathed for a working year, would deliver the occupational ALI
DAC is derived by dividing the ALI (Annual Limit on Intake) by the volume of air breathed in a 2,000-hour working year (2.4 × 10³ m³).
Question 7: What type of air sampler provides real-time, continuous monitoring of airborne radioactivity levels in a controlled area?
- Lapel air sampler with charcoal cartridge
- Continuous air monitor (CAM) with a detector and alarm (Correct answer)
- Impinger sampler for soluble gases
- High-volume cascade impactor
Correct answer: Continuous air monitor (CAM) with a detector and alarm
A CAM draws air through a filter continuously and counts the collected activity in real time, alarming if concentrations reach set points.
NRRPT Contamination and Airborne Control 3
When performing personnel decontamination, which sequence is correct?