United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Mixed Nuclide Classification

HPPOS-289 PDR-9306180280

Title: Mixed Nuclide Classification

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


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


Regulatory references: 10 CFR 61.55

Subject codes: 9.0, 9.4

Applicability: All

Page Last Reviewed/Updated Thursday, March 29, 2012