United States Nuclear Regulatory Commission - Protecting People and the Environment

Health Physics Questions and Answers - Question 71

Question 71: The "Class" column of 10 CFR 20 Appendix B covers inhalation, but does not refer to ingestion. When there are two ALIs for ingestion, how do these relate to the "Class," since they really were based upon the f1 value for gut absorption? (Note: The f1 value is the fractional uptake from the small intestine to blood).

Answer: The ALIs for ingestion do not relate to the "Class," which refers to the retention time in the pulmonary region of the lung. There are two situations for which there are two ALIs for ingestion. One is when the ALI is determined by the non-stochastic dose to an organ. In this case, the organ or tissue to which the limit applies is shown, and the ALI for the stochastic limit is shown in parentheses (for example, see ingestion ALI for beryllium-10). The other case (and the case presumably in question) is when different f1 values were used to calculate the ingestion ALIs. For example, see the entry for cobalt-60, for which the ingestion ALIs are 500 (on the first line) and 200 (on the second line). These ingestion ALI values have no relationship to the corresponding "Class" on the same line (W on the first line and Y on the second line). Rather, as explained in Federal Guidance Report No. 11, these different ingestion ALIs are based on two different f1 values: f1 = 0.05 for ALI = 500, and f1 = 0.3 for ALI = 200. As shown in Federal Guidance Report No. 11, Table 3, f1 = 0.05 for "oxides, hydroxides and trace inorganic," and f1 = 0.3 for "organic complexed and other inorganics." For inhalation of cobalt-60, f1 = 0.05 for both "oxides, hydroxides, halides and nitrates" (class Y), and "all others" (class W).

The following information on Federal Guidance Report No. 11 is provided for those not familiar with this document: The title of this report is "Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors of Inhalation, Submersion and Ingestion." The report is subtitled "Derived Guides for Control of Occupational Exposure and Exposure-to-Dose Conversion Factors for General Application, Based on 1987 Federal Radiation Protection Guidance." The report was published by the U.S. Environmental Protection Agency (EPA) as report number EPA-520 / 1-88-020 on September 1, 1988. The ALI and DAC values in this report are used in Appendix B of the revised Part 20.

(References: 10 CFR 20 Appendix B, Federal Guidance Report No. 11).

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