Document: 10 CFR Part 20
Document ID: f5e61647-ea86-4e01-9cdd-47437f477e62
Document Type: cfr
Title: Determination of internal exposure.
Source: 10 CFR Part 20
Source URL: https://www.ecfr.gov/current/title-10/part-20/section-20.1204
Revision Date: 
Chapter: 
Section ID: 20.1204
CFR Part: 20
CFR Title: 10

Content:
, in order to permit the licensee to make additional measurements basic to the assessments. ( e ) If the identity and concentration of each radionuclide in a mixture are known, the fraction of the DAC applicable to the mixture for use in calculating DAC-hours must be either— ( 1 ) The sum of the ratios of the concentration to the appropriate DAC value (e.g., D, W, Y) from appendix B to part 20 for each radio-nuclide in the mixture; or ( 2 ) The ratio of the total concentration for all radionuclides in the mixture to the most restrictive DAC value for any radionuclide in the mixture. ( f ) If the identity of each radionuclide in a mixture is known, but the concentration of one or more of the radionuclides in the mixture is not known, the DAC for the mixture must be the most restrictive DAC of any radionuclide in the mixture. ( g ) When a mixture of radionuclides in air exists, licensees may disregard certain radionuclides in the mixture if— ( 1 ) The licensee uses the total activity of the mixture in demonstrating compliance with the dose limits in § 20.1201 and in complying with the monitoring requirements in § 20.1502(b) , and ( 2 ) The concentration of any radionuclide disregarded is less than 10 percent of its DAC, and ( 3 ) The sum of these percentages for all of the radionuclides disregarded in the mixture does not exceed 30 percent. ( h ) ( 1 ) In order to calculate the committed effective dose equivalent, the licensee may assume that the inhalation of one ALI, or an exposure of 2,000 DAC-hours, results in a committed effective dose equivalent of 5 rems (0.05 Sv) for radionuclides that have their ALIs or DACs based on the committed effective dose equivalent. ( 2 ) When the ALI (and the associated DAC) is determined by the nonstochastic organ dose limit of 50 rems (0.5 Sv), the intake of radionuclides that would result in a committed effective dose equivalent of 5 rems (0.05 Sv) (the stochastic ALI) is listed in parentheses in table 1 of appendix B to