The U.S. Nuclear Regulatory Commission is in the process of rescinding or revising guidance and policies posted on this webpage in accordance with Executive Order 14151 Ending Radical and Wasteful Government DEI Programs and Preferencing, and Executive Order 14168 Defending Women From Gender Ideology Extremism and Restoring Biological Truth to the Federal Government. In the interim, any previously issued diversity, equity, inclusion, or gender-related guidance on this webpage should be considered rescinded that is inconsistent with these Executive Orders.

Mixed Nuclide Classification

HPPOS-289 PDR-9306180280

See the letter from P.H. Lohaus to S. Arnold (Westinghouse Hanford Co.) dated January 4, 1993.

A request was made for NRC interpretation of the regulatory requirements in 10 CFR Part 61 paragraph 61.55 (a) (5) regarding the classification of wastes containing mixtures of long- and short-lived radionuclides. The question specifically requested clarification on whether radionuclides from both tables of 10 CFR 61.55 should be considered independently. Table 1 of 10 CFR 61.55 contains limits for long-lived radionuclides and Table 2 contains limits for short-lived radionuclides.

The staff position was that the waste generator should calculate the classification of the waste using the sum-of-the-fractions rule separately for the Table 1 isotopes. The following is an acceptable approach to classification of wastes containing both long- and short-lived radionuclides. First, the sum-of-the-fractions for the Table 1 isotopes should be calculated, and then, the sum-of-the-fractions for the Table 2 isotopes should be calculated. If the Table 1 sum does not exceed 0.1, the classification is determined by using Table 2 only. If the Table 1 sum is between 0.1 and 1, and the Table 2 sum is less than 1 for the Column 3 limits, the waste is Class C. In both cases the sums-of-the-fractions are calculated separately for the Table 1 isotopes and the Table 2 isotopes.

Regulatory references: 10 CFR 61.55

Subject codes: 9.0, 9.4

Applicability: All

Page Last Reviewed/Updated Monday, October 30, 2017