NRRPT Radiological Protection Standards 5 — Questions and Answers
Question 1: In 10 CFR Part 835, the dose limit for the lens of the eye for DOE workers is:
- 5 rem/year
- 15 rem/year (Correct answer)
- 25 rem/year
- 50 rem/year
Correct answer: 15 rem/year
10 CFR 835.202 sets the annual occupational dose limit for the lens of the eye at 15 rem (150 mSv) for DOE workers, consistent with NRC limits.
Question 2: NCRP Report No. 151 deals specifically with:
- Structural shielding design for diagnostic X-ray facilities (Correct answer)
- Management of contaminated sites
- Biological effects of low-dose radiation
- Emergency planning for nuclear power stations
Correct answer: Structural shielding design for diagnostic X-ray facilities
NCRP Report No. 151 provides guidance on structural shielding design and evaluation for medical X-ray imaging facilities.
Question 3: The 'planned special exposure' (PSE) provision under 10 CFR 20.1201 allows a worker to receive up to an additional:
- 5 rem in a single event, lifetime limit of 25 rem
- 10 rem in a calendar year, lifetime limit of 25 rem from PSEs (Correct answer)
- 25 rem per calendar year with no lifetime limit
- 15 rem per event, limited to once per year
Correct answer: 10 rem in a calendar year, lifetime limit of 25 rem from PSEs
Under 10 CFR 20.1201(c), a PSE may allow up to 10 rem in a calendar year and must not exceed 25 rem in a lifetime from such exposures.
Question 4: Which quantity is used to express the dose equivalent for regulatory compliance in the U.S. under 10 CFR Part 20?
- Absorbed dose in gray (Gy)
- Equivalent dose in sievert (Sv)
- Dose equivalent in rem or sievert (Correct answer)
- Exposure in roentgen (R)
Correct answer: Dose equivalent in rem or sievert
10 CFR Part 20 uses 'dose equivalent' expressed in rem (or sievert) which incorporates the quality factor, distinct from ICRP's 'equivalent dose' using radiation weighting factors.
Question 5: Under the Linear No-Threshold (LNT) model adopted by ICRP and NCRP, which statement is most accurate?
- There is a safe threshold dose below which no cancer risk exists
- Risk is proportional to dose with no threshold, even at low doses (Correct answer)
- Risk increases exponentially at high doses but is zero below 100 mSv
- Risk applies only to high-LET radiation types
Correct answer: Risk is proportional to dose with no threshold, even at low doses
The LNT model assumes cancer risk is directly proportional to dose with no safe threshold, which forms the regulatory basis for radiation protection standards.
Question 6: What is the regulatory basis for requiring radiation workers to wear dosimetry under 10 CFR Part 20?
- Any worker who enters a radiation area
- Workers likely to receive 10% or more of any applicable limit (Correct answer)
- Only workers classified as Category A radiation workers
- Workers who handle sealed sources exclusively
Correct answer: Workers likely to receive 10% or more of any applicable limit
10 CFR 20.1502 requires monitoring for workers likely to receive 10% or more of any applicable annual dose limit.
Question 7: Which NCRP report specifically addresses the management and disposition of radioactively contaminated soil?
- NCRP Report No. 129 (Correct answer)
- NCRP Report No. 146
- NCRP Report No. 116
- NCRP Report No. 173
Correct answer: NCRP Report No. 129
NCRP Report No. 129 (Recommended Screening Limits for Contaminated Surface Soil, 1999) addresses screening limits and management of radioactively contaminated soil.
NRRPT Radiological Protection Standards 5
In 10 CFR Part 835, the dose limit for the lens of the eye for DOE workers is: