NRRPT Dosimetry and Exposure Control 4 — Questions and Answers
Question 1: A worker's quarterly TEDE is calculated by summing the deep dose equivalent (DDE) and the committed effective dose equivalent (CEDE). If DDE = 300 mrem and CEDE = 120 mrem, what is the TEDE?
- 300 mrem
- 120 mrem
- 420 mrem (Correct answer)
- 180 mrem
Correct answer: 420 mrem
TEDE = DDE + CEDE = 300 mrem + 120 mrem = 420 mrem.
Question 2: The Annual Limit on Intake (ALI) for a radionuclide is defined as the intake that would result in a committed effective dose equivalent of:
- 1 rem (0.01 Sv)
- 5 rem (0.05 Sv) (Correct answer)
- 15 rem (0.15 Sv)
- 50 rem (0.5 Sv)
Correct answer: 5 rem (0.05 Sv)
The ALI is the intake of a radionuclide in a year that would result in a committed effective dose equivalent of 5 rem (0.05 Sv), the annual occupational limit.
Question 3: In whole-body counting, which detection method is most commonly used to measure gamma-emitting internal contamination in a worker?
- Urinalysis
- Nasal swab
- NaI(Tl) or HPGe scintillation/semiconductor detector system (Correct answer)
- Blood sampling
Correct answer: NaI(Tl) or HPGe scintillation/semiconductor detector system
Whole-body counters use large NaI(Tl) scintillators or HPGe detectors to directly measure gamma photons emitted from internal radionuclides.
Question 4: Under the 10 CFR Part 20 dose constraint concept for air emissions, licensees must constrain doses to individual members of the public to what level?
- 100 mrem/yr
- 10 mrem/yr (Correct answer)
- 25 mrem/yr
- 50 mrem/yr
Correct answer: 10 mrem/yr
10 CFR 20.1101(d) requires licensees to constrain airborne radioactive emissions so that doses to individual members of the public do not exceed 10 mrem/yr.
Question 5: Which administrative control sets dose limits lower than regulatory limits to ensure workers don't inadvertently exceed legal limits?
- Derived air concentration (DAC)
- Administrative control level (ACL) (Correct answer)
- Exposure rate factor (ERF)
- Dose commitment factor (DCF)
Correct answer: Administrative control level (ACL)
Administrative control levels (ACLs) are internal organizational limits set below regulatory limits to provide a safety margin and trigger corrective action before limits are exceeded.
Question 6: A Derived Air Concentration (DAC) for an inhalation pathway is defined as the airborne concentration that, if breathed for:
- 8 hours at work rate breathing, results in intake of 1 ALI
- 2000 hours per year at work rate breathing, results in intake of 1 ALI (Correct answer)
- 40 hours per week at light activity, results in 5 rem dose
- 100 hours cumulatively, results in 500 mrem
Correct answer: 2000 hours per year at work rate breathing, results in intake of 1 ALI
DAC is the airborne concentration of a radionuclide that, if inhaled for a full work year (2000 hours) at light work breathing rate, would result in intake of 1 ALI.
Question 7: Which of the following best describes the purpose of a nuclear track etch dosimeter (e.g., CR-39)?
- Measuring low-energy beta particle doses
- Measuring fast neutron doses through recoil proton tracks in plastic (Correct answer)
- Real-time gamma dose rate monitoring
- Detecting alpha contamination on surfaces
Correct answer: Measuring fast neutron doses through recoil proton tracks in plastic
CR-39 track etch dosimeters measure fast neutron doses by detecting the tracks left by recoil protons produced when neutrons interact with hydrogen atoms in the plastic.
NRRPT Dosimetry and Exposure Control 4
A worker's quarterly TEDE is calculated by summing the deep dose equivalent (DDE) and the committed effective dose equivalent (CEDE).
If DDE = 300 mrem and CEDE = 120 mrem, what is the TEDE?