scope:

This standard¹⁾ provides a procedure to measure and index the release rates of non-volatile radionuclides from low-level radioactive waste forms in demineralized water over a test period. It can be applied to any material from which test specimens can be prepared by casting or cutting into a shape for which the surface area and volume can be determined. The results of this procedure do not represent waste form degradation in any specific environmental situation or represent waste form performance. The test method presented in this standard is an adaptation of the method published in the 1986 version of this standard but constrains test parameter values and data analyses to support direct comparisons of test responses of different waste form materials.

Purpose

Standardized and practical methods are required to measure the leaching characteristics of radionuclides from different solidified wastes and to calculate values suitable for comparisons. The leachability of a waste form is not an intrinsic property of a material but is affected by the disposal environment and test conditions. The purpose of this standard is to provide a method for measuring the leaching response of a material under specified test conditions and to present mathematical procedures for calculating a material-specific "leachability index" value that is appropriate for relative comparisons. This standard is intended to serve as a basis for indexing the relative radionuclide retention in different solidified low-level radioactive waste forms by using a short-term (5-day) test conducted under controlled conditions.

The test responses are not intended to represent the leaching behavior of a waste form in a disposal system because the test does not account for the material degradation mechanism or environmental effects. Under disposal conditions, processes other than leaching (chemical reactions, formation of surface layers and films, cracking, etc.) might be important considerations. Moreover, the interplay of retardation mechanisms (filtration, ion exchange, coprecipitation, etc.) and enhancement mechanisms (chelation, desorption, dissolution, etc.) might be important considerations for radionuclide migration.

¹⁾ The current standard, ANSI/ANS-16.1-2019, is hereinafter referred to as "this standard."