A proposed ASTM standard practice for the prediction of long-term behavior of waste package materials in a geologic repository

Subcommittee C26.13, Repository Waste Package Materials Testing of the American Society for Testing Materials (ASTM) has been investigating the problem of making long term predictions of the behavior of materials that will be used in a geologic repository for high-level nuclear waste. Since radionuclides in the waste forms (currently spent nuclear fuel and borosilicate glass) must be contained for thousands of years, predictions of materials behavior are needed over the same extended periods of time. Such predictions present unique problems to scientists. The ASTM provides an appropriate forum for reaching a consensus solution to this problem since nuclear waste producers and receivers, licensing agencies, and general interest scientific groups are represented. The Subcommittee is now nearing completion of a Standard Practice on this subject. The purpose of this paper is to introduce the scientific community to the proposed Standard Practice. The Standard is based on development of a model for the alteration of the material in repository service. As much as possible, the model is based on a mechanistic understanding of the alteration modes. The model is then used to predict the long-term behavior of the material. 25 refs., 2 figs