CRI Safety Standards & Quality Control 3 — Questions and Answers
Question 1: What is the maximum permissible occupational radiation dose to the whole body per year under 10 CFR Part 20?
- 1 rem (10 mSv)
- 5 rem (50 mSv) (Correct answer)
- 2 rem (20 mSv)
- 10 rem (100 mSv)
Correct answer: 5 rem (50 mSv)
10 CFR 20.1201 limits occupational whole-body dose to 5 rem (50 mSv) per year for radiation workers.
Question 2: Film darkroom safelights used during radiographic film processing must be verified using a:
- Densitometer check on processed film
- Coin or paper fog test (Correct answer)
- Step-wedge sensitometric strip
- Radiation survey meter
Correct answer: Coin or paper fog test
The coin or paper fog test checks whether safelight conditions cause measurable fog on unexposed film, ensuring darkroom integrity.
Question 3: Which type of radiation is most effectively shielded by lead and dense concrete?
- Alpha particles
- Beta particles
- Gamma rays (Correct answer)
- Neutron radiation
Correct answer: Gamma rays
Gamma rays require dense shielding materials like lead or thick concrete because of their high penetrating power and electromagnetic nature.
Question 4: The 'inverse square law' states that radiation intensity is inversely proportional to:
- Source activity
- The square of the distance from the source (Correct answer)
- Film speed
- Exposure time
Correct answer: The square of the distance from the source
Radiation intensity decreases with the square of the distance: doubling the distance reduces intensity to one-quarter of its original value.
Question 5: During radiographic operations in a restricted area, the radiation level at the boundary must not exceed:
- 2 mR/hr
- 5 mR/hr
- 10 mR/hr
- 2 mR in any one hour (Correct answer)
Correct answer: 2 mR in any one hour
10 CFR 34.43(a) requires that the dose rate at the boundary of the restricted area not exceed 2 mR in any one hour for areas where individuals may receive more than 5 rem/year.
Question 6: A radiographer discovers their TLD badge was left in the vehicle during an exposure. The correct action is to:
- Estimate dose and add to records
- Treat the dose as zero for that period
- Report the badge as lost/damaged and follow the employer's anomalous dosimetry procedure (Correct answer)
- Subtract from the next month's reading
Correct answer: Report the badge as lost/damaged and follow the employer's anomalous dosimetry procedure
A badge not worn during an exposure is treated as a dosimetry anomaly; the employer must follow NRC-required procedures for estimating and recording dose.
Question 7: What is the purpose of a 'step-wedge' sensitometric strip in radiographic film quality control?
- To measure source activity
- To verify developer chemical concentration
- To monitor film processor performance over time (Correct answer)
- To calibrate the densitometer light source
Correct answer: To monitor film processor performance over time
Daily sensitometric strips processed under standard conditions allow trending of developer activity, temperature, and replenishment rate to detect processor drift.
CRI Safety Standards & Quality Control 3
What is the maximum permissible occupational radiation dose to the whole body per year under 10 CFR Part 20?