Performance assessment methodologies for the analysis of high-level nuclear waste repositories

The Nuclear Waste Policy Act of 1982 requires the US Nuclear Regulatory Commission (NRC) to evaluate a license application submitted by the US Department of Energy to construct high-level nuclear waste (HLW) repositories. The basis that NRC will use to determine the suitability of a potential HLW disposal site is the independent assessment of compliance with existing federal regulations. The regulations set forth in NRC rule 10CFR60 and in the US Environmental Protection Agency's standard 40CFR191 include criteria that must be met to ensure the effective long-term isolation of the waste by the multiple-barrier system (repository and geologic formation) and to minimize the release of radioactivity to the accessible environment. Since 1976, the NRC has contracted to Sandia National Laboratories (SNL) in Albuquerque, New Mexico, the development of methodologies that the NRC will use to assess the performance of HLW repositories. To date, SNL has developed two methodologies: one for bedded-salt formations and another for basalt formations. Work is currently under way to develop a methodology applicable to welded-tuff formations.