RSO Radiation Sources and Equipment Safety 1 — Questions and Answers
Question 1: A sealed source is defined as radioactive material that is:
- Below exempt quantity limits
- Permanently bonded or encapsulated in a container that prevents dispersal under normal conditions (Correct answer)
- Stored in a locked cabinet when not in use
- Used only in industrial applications
Correct answer: Permanently bonded or encapsulated in a container that prevents dispersal under normal conditions
A sealed source contains radioactive material permanently encapsulated or fixed in a solid form or sealed container designed to prevent dispersal under normal and reasonably foreseeable accident conditions.
Question 2: How frequently must sealed sources used in industrial radiography be tested for leakage under NRC regulations?
- Monthly
- Every 6 months (Correct answer)
- Annually
- Every 3 years
Correct answer: Every 6 months
NRC regulations (10 CFR 34.27) require that sealed sources used in industrial radiography be tested for leakage at intervals not to exceed 6 months.
Question 3: A leak test of a sealed source showing contamination of 185 Bq (0.005 µCi) or more requires the RSO to:
- Continue using the source but increase survey frequency
- Immediately remove the source from service and notify the NRC (Correct answer)
- Perform a second confirmatory swipe before taking action
- Document the result and retest in 30 days
Correct answer: Immediately remove the source from service and notify the NRC
Under NRC regulations, a leak test result of 185 Bq (0.005 µCi) or greater indicates a leaking source that must be immediately removed from service, stored safely, and the event reported to the NRC.
Question 4: A radiation-producing machine (e.g., an X-ray tube) differs from a radioactive source in that it:
- Produces radiation only when energized and poses no hazard when powered off (Correct answer)
- Requires a radioactive source license from the NRC
- Cannot be shielded with lead
- Produces only gamma radiation
Correct answer: Produces radiation only when energized and poses no hazard when powered off
Radiation-producing machines generate ionizing radiation only when electrically energized; unlike radioactive sources, they pose no radiation hazard when switched off because there is no radioactive material present.
Question 5: The purpose of a radiation area posting requirement (NRC Caution: Radiation Area sign) is triggered when dose rates could exceed:
- 0.05 mSv/h (5 mrem/h) at 30 cm (Correct answer)
- 1 mSv/h (100 mrem/h) at 30 cm
- 2 mSv/h (200 mrem/h) at any accessible point
- 0.01 mSv/h (1 mrem/h) at the area boundary
Correct answer: 0.05 mSv/h (5 mrem/h) at 30 cm
Under 10 CFR 20.1901, a Radiation Area is defined where dose rates could exceed 0.05 mSv/h (5 mrem/h) at 30 cm from the source or accessible surface, requiring a 'Caution: Radiation Area' posting.
Question 6: What is the primary hazard associated with high-activity Ir-192 sources used in industrial gamma radiography?
- Internal contamination from radioactive gas release
- High external dose rates leading to acute radiation exposure if the source is not properly controlled (Correct answer)
- Beta skin burns at normal working distances
- Neutron activation of surrounding materials
Correct answer: High external dose rates leading to acute radiation exposure if the source is not properly controlled
Ir-192 is a high-activity gamma emitter; if the source becomes stuck outside its shielded container or is handled without proper controls, workers can receive severe acute doses at typical working distances.
RSO Radiation Sources and Equipment Safety 1
A sealed source is defined as radioactive material that is: