NRRPT Internal Dosimetry and Bioassay 1 — Questions and Answers
Question 1: What is the primary purpose of bioassay in radiation protection?
- To measure external radiation dose rates
- To estimate internal radioactive material uptake in workers (Correct answer)
- To calibrate survey instruments
- To assess environmental contamination levels
Correct answer: To estimate internal radioactive material uptake in workers
Bioassay programs detect and quantify radionuclides inside the body to estimate internal dose commitments from inhalation or ingestion.
Question 2: Which type of bioassay measures radioactivity directly in the body using external detectors?
- Indirect bioassay
- In-vitro bioassay
- In-vivo bioassay (Correct answer)
- Excretion bioassay
Correct answer: In-vivo bioassay
In-vivo bioassay uses whole-body or lung counters to directly detect gamma and X-ray emissions from radionuclides inside the body.
Question 3: Which route of internal contamination typically delivers the highest dose for most radionuclides encountered in nuclear facilities?
- Ingestion
- Skin absorption
- Inhalation (Correct answer)
- Wound entry
Correct answer: Inhalation
Inhalation is the most significant route for most workplace radionuclides because aerosols and gases are readily drawn deep into the lungs.
Question 4: What does the committed effective dose equivalent (CEDE) represent?
- The dose received in a single acute exposure event
- The 50-year dose commitment from a single intake of radioactive material (Correct answer)
- The cumulative external dose over a career
- The dose limit for a controlled area
Correct answer: The 50-year dose commitment from a single intake of radioactive material
CEDE is the 50-year integrated effective dose resulting from a single intake event, accounting for the long-term retention and decay of the radionuclide.
Question 5: What is the derived air concentration (DAC) used for in internal dosimetry?
- To set external dose rate limits in controlled areas
- To establish the airborne concentration that equals one ALI when inhaled for a full work year (Correct answer)
- To measure stack effluent activity
- To calibrate air samplers
Correct answer: To establish the airborne concentration that equals one ALI when inhaled for a full work year
The DAC is the airborne radionuclide concentration that, if breathed for 2,000 hours, would deliver one annual limit on intake (ALI).
Question 6: What is the annual limit on intake (ALI) based on for occupational workers?
- The dose that doubles the cancer risk in a population
- The intake that results in a committed effective dose of 5 rem or a committed dose equivalent of 50 rem to any organ (Correct answer)
- The maximum airborne concentration permissible
- The NRC's emergency dose limit
Correct answer: The intake that results in a committed effective dose of 5 rem or a committed dose equivalent of 50 rem to any organ
ALI is the lesser of the intake yielding 5 rem CEDE to the whole body or 50 rem committed dose equivalent to any single organ or tissue.
NRRPT Internal Dosimetry and Bioassay 1
What is the primary purpose of bioassay in radiation protection?