NDT Radiographic Testing Safety 2 — Questions and Answers
Question 1: What is the primary unit used to measure absorbed radiation dose in tissue?
- Roentgen (R)
- Gray (Gy) (Correct answer)
- Becquerel (Bq)
- Sievert (Sv)
Correct answer: Gray (Gy)
The Gray (Gy) measures absorbed dose, defined as one joule of energy absorbed per kilogram of tissue.
Question 2: Which type of radiation has the greatest penetrating power?
- Alpha particles
- Beta particles
- Gamma rays (Correct answer)
- Neutrons
Correct answer: Gamma rays
Gamma rays are highly penetrating electromagnetic radiation requiring dense shielding materials like lead or concrete.
Question 3: What does ALARA stand for in radiographic testing safety?
- Always Limit All Radiation Amounts
- As Low As Reasonably Achievable (Correct answer)
- Approved Levels of Allowable Radiation Activity
- Authorized Limits for Acceptable Radiation Areas
Correct answer: As Low As Reasonably Achievable
ALARA is the guiding principle that radiation exposure should be kept as low as reasonably achievable through time, distance, and shielding.
Question 4: A radiographer is setting up an exposure. Doubling the distance from the source reduces the dose rate by approximately:
- 25% of the original (Correct answer)
- 50% of the original
- 75% of the original
- The dose rate is unchanged
Correct answer: 25% of the original
Per the inverse square law, doubling the distance reduces dose rate to one-quarter (25%) of the original value.
Question 5: Which regulatory body in the US sets occupational radiation dose limits for NDT workers?
- OSHA
- NRC (Nuclear Regulatory Commission) (Correct answer)
- EPA
- ASNT
Correct answer: NRC (Nuclear Regulatory Commission)
The NRC sets occupational radiation dose limits under 10 CFR Part 20, which governs the use of radioactive materials in industry.
Question 6: What is the annual whole-body occupational dose limit for radiation workers in the US?
- 1 mSv (100 mrem)
- 5 mSv (500 mrem)
- 50 mSv (5 rem) (Correct answer)
- 100 mSv (10 rem)
Correct answer: 50 mSv (5 rem)
The NRC limits occupational whole-body dose to 50 mSv (5 rem) per year under 10 CFR Part 20.
Question 7: Which shielding material is most effective per unit thickness for gamma radiation from Ir-192?
- Aluminum
- Concrete
- Lead (Correct answer)
- Polyethylene
Correct answer: Lead
Lead's high atomic number and density make it the most effective per-unit-thickness shield against gamma radiation from industrial sources like Ir-192.
NDT Radiographic Testing Safety 2
What is the primary unit used to measure absorbed radiation dose in tissue?