Health Physics Questions and Answers - Question 54
Question 54: Must bioassay be performed for a worker who, without respiratory protection, is likely to receive an intake in excess of the applicable ALI (s) but who is not likely to receive such an intake with respiratory protection?
Answer: A "Note" in the statement of considerations (56 FR 23377, column 2) says that ". . . the concentrations to be used for evaluating monitoring thresholds are those of the ambient atmosphere before credit is taken for respiratory protective factors." That note is a conservative assumption that is appropriate if there will be no "further verification" that the assigned respiratory protection factors actually will be achieved.
At nuclear power plants, if the "surveys and bioassays, as appropriate," required by 10 CFR 20.1703 (a) (3) (ii), include reasonable measures to verify that the expected degree of respiratory protection will be achieved, "the concentrations to be used for evaluating monitoring thresholds" may be those that include credit for the protection factors when respirators are to be used. Measures to verify that the expected degree of respiratory protection has been achieved may 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 representative 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.
At fuel cycle and materials facilities using large quantities of unsealed radioactive materials, the nature of the operations is such that bioassays are required for workers who are likely to receive an intake in excess of ten percent of the applicable ALIs without respiratory protection. Because of the types and quantities of radioactive airborne particulates at fuel cycle and materials licensees, it is advisable to not take credit for respiratory protection factors when determining if monitoring (e.g., bioassay) is required. NRC will consider licensee proposals to allow using respiratory protection factors when determining if internal dose monitoring is required, if the licensee demonstrates a verification method that the respiratory protection factor is actually achieved for all workers wearing respirators. Unless authorized in the license, fuel cycle and materials licensees should understand that the threshold level for monitoring in 10 CFR 20.1502 (b) is ten percent of the applicable ALIs without credit for respirators.
(Reference: 10 CFR 20.1502 (b), 10 CFR 20.1703)