This test method measures mass transport from a cylindrical solidified waste form into water under conditions that accelerate leaching. Test parameters, such as the volume of leachant and the frequency at which the leachant is changed, have been optimized to eliminate experimental effects (for example, saturation effects that can complicate modeling of the net forward diffusion rate).

This test method can be used to:

5.2.1 Provide diffusion coefficients for waste forms;

5.2.2 Obtain higher fraction releases than can be achieved with expected service conditions for greater confidence in waste form properties;

5.2.3 Obtain measurable leachate concentrations from materials that have very low release rates under service conditions; and

5.2.4 Compare releases from various types of solidification agents and formulations.

Modeling the experimental observations obtained in the test allows the extrapolation of leaching results to long times and to full-scale waste forms under the following constraints:

5.3.1 Results of this test method cannot be taken to apply to releases in specific disposal environments unless tests are conducted to determine the leaching mechanism under those conditions.

5.3.2 Projections of releases require the long-term stability of the waste form, which may or may not be indicated adequately by short-term tests.

5.3.3 Extrapolations are limited to the maximum CFL obtained with the accelerated test.

5.3.4 The leaching mechanisms observed in tests conducted at elevated temperatures must be the same as the mechanisms observed in the tests run at the reference temperature.

1.1 This test method provides a method for accelerating the leach rate of solidified waste and determining if the release is diffusion-controlled. This test method is applicable to any material that does not degrade, deform, or change leaching mechanism during the test.

1.1.1 If diffusion is the dominant leaching mechanism, then results of this test can be used to model long-term releases from waste forms. Diffusion can be confirmed as the leaching mechanism through the use of a computerized mathematical model for diffusion from the finite cylinder (Note 1).

1.1.2 The leaching mechanism should be verified as diffusion-controlled by a means other than analysis of the leach test data. For this purpose, analysis of post-leaching concentration profiles within the solid waste form is recommended.

Note 1—The computer program and the models are briefly described in and in the Accelerated Leach Test Method and User's Guide for the "ALT" Computer Program (1).

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.