CRI Radiation Safety & Protection 3 — Questions and Answers
Question 1: A radiographer is working with an Ir-192 source. What is the approximate half-life of Ir-192?
- 14 days
- 30 years
- 74 days (Correct answer)
- 5.3 years
Correct answer: 74 days
Iridium-192 has a half-life of approximately 74 days, requiring periodic source replacement.
Question 2: What minimum survey meter reading at the surface of a radiography camera indicates the source is fully retracted?
- Background level only (Correct answer)
- 2 mSv/hr
- 5 mSv/hr
- 10 mSv/hr
Correct answer: Background level only
When the source is fully retracted, readings should return to background levels at the device surface.
Question 3: Which regulation governs the transportation of radioactive materials by road in the United States?
- 49 CFR Part 173 (Correct answer)
- 10 CFR Part 34
- 29 CFR 1910.1096
- 21 CFR Part 900
Correct answer: 49 CFR Part 173
49 CFR Part 173 (DOT regulations) governs the classification and packaging of hazardous materials including radioactive sources during transport.
Question 4: What does a transport index (TI) of 1.0 on a radioactive package indicate?
- The dose rate at 1 meter is 1 mSv/hr
- The dose rate at 1 meter is 0.1 mSv/hr (Correct answer)
- The package weighs 1 kg
- The source has an activity of 1 Ci
Correct answer: The dose rate at 1 meter is 0.1 mSv/hr
A TI of 1.0 means the maximum dose rate at 1 meter from the package surface is 0.1 mSv/hr (10 mrem/hr).
Question 5: In industrial radiography, what is the purpose of the source guide tube?
- To collimate the beam toward the film
- To guide the source to the exposure position (Correct answer)
- To store the source during transport
- To measure source activity
Correct answer: To guide the source to the exposure position
The source guide tube directs and positions the source at the desired exposure location away from the camera body.
Question 6: Which type of radiation interaction is responsible for most of the ionization caused by beta particles in tissue?
- Compton scattering
- Pair production
- Direct ionization (Correct answer)
- Photoelectric effect
Correct answer: Direct ionization
Beta particles cause ionization primarily through direct Coulombic interactions with orbital electrons in tissue.
Question 7: A radiographer discovers a locked-jaw condition during a field operation. What is the FIRST action to take?
- Attempt to manually retract the source
- Evacuate the area and establish a barrier (Correct answer)
- Call the device manufacturer
- Perform a survey to determine dose rates
Correct answer: Evacuate the area and establish a barrier
The immediate priority is to evacuate all personnel and establish a safety barrier to prevent additional exposure.
CRI Radiation Safety & Protection 3
A radiographer is working with an Ir-192 source.
What is the approximate half-life of Ir-192?