RSO Dosimetry and Personal Exposure Assessment 1 — Questions and Answers
Question 1: A thermoluminescent dosimeter (TLD) measures radiation exposure by:
- Ionizing gas in a sealed chamber
- Storing energy in crystal lattice defects released as light when heated (Correct answer)
- Darkening photographic film proportional to dose
- Counting individual photon interactions electronically
Correct answer: Storing energy in crystal lattice defects released as light when heated
TLDs work by trapping radiation-induced electrons in crystal lattice defects; when heated, trapped electrons release their stored energy as measurable light proportional to dose.
Question 2: The NRC annual occupational whole-body dose limit (TEDE) for radiation workers is:
- 5 mSv (0.5 rem)
- 50 mSv (5 rem) (Correct answer)
- 100 mSv (10 rem)
- 20 mSv (2 rem)
Correct answer: 50 mSv (5 rem)
10 CFR 20.1201 establishes the annual occupational total effective dose equivalent (TEDE) limit at 50 mSv (5 rem) for adults working with radiation.
Question 3: An optically stimulated luminescence (OSL) dosimeter differs from a TLD primarily because it:
- Requires no reader and gives a direct digital display
- Releases stored dose information using light rather than heat (Correct answer)
- Only measures neutron dose
- Cannot be reread after initial processing
Correct answer: Releases stored dose information using light rather than heat
OSL dosimeters use laser light rather than heat to stimulate the release of trapped electrons, which then emit light proportional to the accumulated dose.
Question 4: When should a radiation worker wear their dosimeter at the collar level rather than at the waist?
- When working with pure beta emitters only
- When wearing a lead apron in fluoroscopy or other high-dose-rate x-ray environments (Correct answer)
- When monitoring for neutron dose
- When the whole-body dose is expected to exceed 50 mSv
Correct answer: When wearing a lead apron in fluoroscopy or other high-dose-rate x-ray environments
During fluoroscopy with a lead apron, a collar badge worn outside the apron monitors the unshielded head and neck dose; a second badge under the apron may estimate effective dose.
Question 5: A deep dose equivalent (DDE) reported on a dosimeter badge refers to dose at a tissue depth of:
- 0.007 cm (70 µm) for skin
- 0.3 cm for lens of eye
- 1.0 cm for deep tissue/organs (Correct answer)
- 5.0 cm for bone marrow
Correct answer: 1.0 cm for deep tissue/organs
Deep dose equivalent is the dose equivalent at 1 cm depth in tissue, representing dose to deep organs and used in calculating TEDE for external radiation.
Question 6: A Geiger-Müller (GM) survey meter is best suited for:
- Accurately measuring high dose rates above 1 Gy/h
- Detecting the presence of low-level beta/gamma contamination (Correct answer)
- Measuring neutron fluence rates
- Quantifying alpha emitters through intact clothing
Correct answer: Detecting the presence of low-level beta/gamma contamination
GM detectors are extremely sensitive and ideal for detecting contamination and low-level beta/gamma radiation, though they can 'dead-time' saturate at high dose rates.
RSO Dosimetry and Personal Exposure Assessment 1
A thermoluminescent dosimeter (TLD) measures radiation exposure by: