U.S. Nuclear Regulatory Commission
Question 375: In supporting a conclusion that individual monitoring of internal occupational dose is not required [10 CFR 20.1502 (b)] and, therefore, that summing of internal and external dose is not required [10 CFR 20.1202 (a)], what is considered to be acceptable for bioassay frequency, DAC-hour administrative limit, and whole-body counting minimum testing level?
Answer: Under 10 CFR 20.1502 (b), there is no required frequency for bioassay, DAC-hour administrative limit, or minimum testing level for whole-body counting either for individuals for whom monitoring is required or to support a conclusion that individual monitoring is not required. However, the answer to Question 54 provided a number of examples of measures that could be used at nuclear power plants to verify that the expected degree of respiratory protection will be achieved so that the concentrations of radionuclides in air after credit is taken for respiratory protection may be used in making the prospective assessment that individual monitoring for internal dose is not required. These measures "include, (but are not limited to) measurements of nasal smears from workers who have used respirators and whole body counting, relatively soon after a job, of one or more workers among a group of workers who wore respiratory protective equipment while working on the job and periodic whole-body counting (e.g., annually) of all workers who wear respiratory protective equipment."
It should be recognized that in addition to the bioassay requirements of 10 CFR 20.1502 (b), there is the bioassay requirement of 10 CFR 20.1703 (a) (3) (ii), which is related to the use of individual respiratory protection equipment. If whole body counting is to be used to verify the effectiveness of the respiratory protection program, it must be able to demonstrate that estimates of intake based on exposure calculations (i.e., on air concentrations and on taking credit for protection factors) are consistent with estimates of intake based on bioassay. The licensee should take into account the fact that demonstrating effectiveness of the respiratory protection program may have to be based on exposures over durations much shorter than a year, particularly for materials that are expected to be cleared rapidly from the body. Some general guidance on air sampling is provided in Regulatory Guide 8.25, Rev. 1, (which states that this guide does not apply to reactor facilities), and general guidance on bioassay will be provided in Regulatory Guide 8.9, Rev. 1.
(References: 10 CFR 20.1502, 10 CFR 20.1202, 10 CFR 20.1703, Regulatory Guide 8.9)