Demonstration of a Performance Assessment Methodology for Nuclear Waste Isolation in Basalt Formations

摘要

This paper summarizes the results of the demonstration of a performance assessment methodology developed by Sandia National Laboratories, Albuquerque for the US Nuclear Regulatory Commission for use in the analysis of high-level radioactive waste disposal in deep basalts. Seven scenarios that could affect the performance of a repository in basalts were analyzed. One of these scenarios, normal ground-water flow, was called the base-case scenario. This was used to demonstrate the modeling capabilities in the methodology necessary to assess compliance with the ground-water travel time criterion. The scenario analysis consisted of both scenario screening and consequence modeling. Preliminary analyses of scenarios considering heat released from the waste and the alteration of the hydraulic properties of the rock mass due to loads created by a glacier suggested that these effects would not be significant. The analysis of other scenarios indicated that those changing the flow field in the vicinity of the repository would have an impact on radionuclide discharges, while changes far from the repository may not be significant. The analysis of the base-case scenario was used to show the importance of matrix diffusion as a radionuclide retardation mechanism in fractured media. The demonstration of the methodology also included an overall sensitivity analysis to identify important parameters and/or processes. 15 refs., 13 figs., 2 tabs. (ERA citation 13:017815)