Methodology for identifying credible disruptions to isolation of nuclear waste within Columbia River basalts

Analysis of potential preclosure and postclosure disruptive events and processes is comprised of evaluation of (1) potential uncertainties and omissions associated with characterization of the site; (2) credible events and processes resulting from the dynamics of natural systems; (3) potential, credible changes in isolation conditions induced by the presence of the repository, and (4) potential, credible future changes impacting isolation capability resulting from man's activities, independent of repository construction/operation. This report presents the overall methodology for identification, classification and analysis of disruptive events based on Nuclear Regulatory Commission and Environmental Protection Agency guidelines proposed in drafts of 10 CFR 60 and 40 CFR 191. Potential credible disruptive events, processes, and conditions are considered with respect to whether they are anticipated or unanticipated, and determined to have reasonably foreseeable, very unlikely, or extremely unlikely probability of occurrence. 85 refs., 2 figs., 7 tabs