NRRPT Dosimetry and Exposure Control 3 â Questions and Answers
Question 1: The shallow dose equivalent (SDE) measures dose at a tissue depth of:
- 0.007 cm (70 micrometers) (Correct answer)
- 1 cm (1000 micrometers)
- 10 cm
- 0.3 cm
Correct answer: 0.007 cm (70 micrometers)
The shallow dose equivalent is measured at a tissue depth of 0.007 cm (70 Ξm), representing the dose to the skin and extremities.
Question 2: A photon dose rate of 2.5 mGy/hr has a radiation weighting factor of 1. What is the equivalent dose rate in mSv/hr?
- 0.25 mSv/hr
- 1.0 mSv/hr
- 2.5 mSv/hr (Correct answer)
- 25 mSv/hr
Correct answer: 2.5 mSv/hr
For photons, the radiation weighting factor (wR) is 1, so equivalent dose (mSv) = absorbed dose (mGy) Ã 1 = 2.5 mSv/hr.
Question 3: Which type of dosimeter provides an immediate reading of accumulated dose and can be reset after each use?
- TLD
- Film badge
- OSL dosimeter
- Self-reading pocket dosimeter (Correct answer)
Correct answer: Self-reading pocket dosimeter
Self-reading (direct-reading) pocket dosimeters display accumulated dose immediately and can be zeroed and reused after each shift.
Question 4: The NRC requires that personnel dosimetry be provided to radiation workers whose dose in any calendar year is likely to exceed what fraction of the occupational limit?
- 1/10 (10%) (Correct answer)
- 1/4 (25%)
- 1/2 (50%)
- 1/100 (1%)
Correct answer: 1/10 (10%)
10 CFR 20.1502 requires dosimetry for workers likely to receive more than 10% (1/10) of the applicable annual dose limit.
Question 5: What is the purpose of using a control dosimeter (control badge) in a personnel dosimetry program?
- To measure the dose at the highest exposure location
- To establish background radiation levels and detect processing artifacts (Correct answer)
- To calibrate survey instruments
- To measure neutron dose separately from gamma dose
Correct answer: To establish background radiation levels and detect processing artifacts
Control dosimeters are kept in an unoccupied, low-radiation area to account for background and any processing-related response so it can be subtracted from worker readings.
Question 6: A worker receives an unplanned whole-body dose of 6 rem in a single incident. Under NRC regulations, this must be reported as:
- A significant event requiring immediate shutdown
- An overexposure reportable to the NRC (Correct answer)
- An ALARA exceedance only
- No report required unless it exceeds 25 rem
Correct answer: An overexposure reportable to the NRC
10 CFR 20.2203 requires reporting to the NRC when a worker receives a dose exceeding 5 rem (0.05 Sv) total effective dose equivalent in a year.
Question 7: Which of the following radionuclides is commonly used as a source for calibrating gamma dosimeters due to its stable 662 keV photon energy?
- Co-60
- Cs-137 (Correct answer)
- Am-241
- Na-22
Correct answer: Cs-137
Cs-137 emits a stable, well-characterized 662 keV gamma ray making it ideal for dosimeter calibration in health physics.
NRRPT Dosimetry and Exposure Control 3
The shallow dose equivalent (SDE) measures dose at a tissue depth of: