NRRPT Radioactive Material Control 4 — Questions and Answers
Question 1: A worker handles an open vial of I-131 solution without gloves and later tests positive for thyroid uptake. Which route of intake is MOST likely responsible?
- External beta irradiation of the hands
- Ingestion via hand-to-mouth contact
- Inhalation of volatile iodine vapor (Correct answer)
- Skin absorption through intact epidermis
Correct answer: Inhalation of volatile iodine vapor
I-131 readily volatilizes from solution, making inhalation the predominant intake route in open handling situations without respiratory protection.
Question 2: Which label is required on a package containing radioactive material with a transport index of 3.2?
- White-I label
- Yellow-II label
- Yellow-III label (Correct answer)
- Radioactive LSA label
Correct answer: Yellow-III label
A transport index between 1.0 and 10 requires a Yellow-III label; Yellow-II is for TI > 0 but ≤ 1.0; Yellow-III covers TI > 1.0 up to 10.
Question 3: What is the purpose of a 'step-off pad' at the exit of a contaminated area?
- To absorb liquid spills before they reach the floor drain
- To provide a clean surface where workers change footwear and check for foot contamination (Correct answer)
- To reduce dose rate to workers exiting the area
- To collect smear samples for routine contamination surveys
Correct answer: To provide a clean surface where workers change footwear and check for foot contamination
Step-off pads define the transition zone where workers remove potentially contaminated shoe covers and survey their feet before entering uncontrolled areas.
Question 4: A decommissioning project wants to release a building for unrestricted use. The applicable NRC criterion for surface contamination release is based on:
- Total activity remaining on all surfaces combined
- Dose to a hypothetical maximally exposed individual not exceeding 25 mrem/year (Correct answer)
- Dose rate not exceeding 2 mR/hr at 30 cm from any surface
- Background radiation levels in the adjacent neighborhood
Correct answer: Dose to a hypothetical maximally exposed individual not exceeding 25 mrem/year
NRC's license termination rule (10 CFR 20 Subpart E) sets a 25 mrem/year total effective dose equivalent (TEDE) criterion for unrestricted release of facilities.
Question 5: Tritium (H-3) presents a unique internal dose hazard primarily because:
- It emits high-energy gamma radiation that escapes the body
- As water (HTO) it distributes uniformly throughout total body water (Correct answer)
- It concentrates selectively in bone mineral like Ra-226
- Its long 12.3-year half-life means it persists in tissue for decades
Correct answer: As water (HTO) it distributes uniformly throughout total body water
Tritiated water is absorbed rapidly and distributes throughout all body water compartments, irradiating all soft tissues with a biological half-life of about 10 days.
Question 6: Under 10 CFR 20, which of the following correctly identifies when a Radiation Work Permit (RWP) or equivalent authorization is typically required?
- Only when external dose rates exceed 5 rem/hr
- When entering a High Radiation Area or performing non-routine work with radioactive material (Correct answer)
- Whenever a worker carries a personal dosimeter
- Only for licensed operators working with sealed sources
Correct answer: When entering a High Radiation Area or performing non-routine work with radioactive material
RWPs are administrative controls used to authorize entry into elevated radiation or contamination areas and to define protective measures for non-routine or higher-hazard tasks.
Question 7: What is the recommended frequency for calibrating portable radiation survey instruments used in routine health physics programs?
- Daily before each use
- At intervals not to exceed 12 months, with source checks before each use (Correct answer)
- Quarterly regardless of use frequency
- Only after suspected damage or anomalous readings
Correct answer: At intervals not to exceed 12 months, with source checks before each use
NRC regulations (10 CFR 20.1501) and ANSI standards require calibration at least annually, with operability source checks performed before each use.
NRRPT Radioactive Material Control 4
A worker handles an open vial of I-131 solution without gloves and later tests positive for thyroid uptake.
Which route of intake is MOST likely responsible?