Answer to Question #2416 Submitted to "Ask the Experts"

Q

In regard to 10 CFR 20.2003, I would like to know: (a) for three and four types of radioactive liquid waste disposal to the sewer system, what is the unity rule to show that the amount of radioactivity does not exceed the total annual limits for ³H, ¹⁴C, and the sum of other isotopes?

A

As required by 10 CFR 20.2003(a)(3), if more than one radionuclide is released, the following conditions must also be satisfied:

(i) the licensee shall determine the fraction of the limit in Table 3 of Appendix B to Part 20 represented by discharges into the sanitary sewerage by dividing the actual monthly average concentration of each radionuclide released by the licensee into the sewer by the concentration of that radionuclide listed in Table 3 of Appendix B to Part 20, and (ii) the sum of the fractions for each radionuclide required by paragraphs (a)(3)(i) of this section does not exceed unity.

This condition can be expressed as follows:

C1/Tabulated Value 1 + C2/Tabulated Value 2 + . . . must be < or = 1,

where C(i) is the average monthly concentration of nuclide i, and Tabulated Value i is the value of the concentration of that radionuclide listed in Table 3 of Appendix B to Part 20.

As for the requirement in subsection 10 CFR 20.2003(a) (4), the total quantity of licensed and other radioactive material that the licensee releases into the sanitary sewerage in a year, this cannot exceed 5 curies (185 GBq) of ³H, 1 curie (37 GBq) of ¹⁴C, and 1 curie (37 GBq) of all other radioactive materials combined.

In addition to the average monthly concentrations to those shown in Table 3, Appendix B, and as described in (3)(i) and (3)(ii) above, the licensee must also submit the total quantities of radioactive material released to the sewer during the year to those stated in this paragraph.

Cynthia G. Jones, PhD
Nuclear Regulatory Commission