Conclusions from the SKI repository performance assessment research project site-94

The Swedish Nuclear Power Inspectorate, SKI, has recently completed a performance assessment research project, SITE-94. The project was formally set up as an assessment of a hypothetical repository for spent nuclear fuel, and used site field data from the pre-excavation phase of the Aspo Hard Rock Laboratory. The project has been concentrated in developing methods for site evaluation, performance assessment methodology and canister analysis. In applying the developed methods the results were factored into calculations of radionuclide release and transport, but these calculations do not represent a full performance assessment. The achievements include development of a systems approach to performance assessment using tools like process system influence diagrams (PID) and relational databases to capture expert opinions on the most important interactions between features, events and process in the repository system, development of a site evaluation methodology which attempts at capturing all relevant field information and producing a consistent geo-mechanical-hydrological-chemical model of the site, and identification of mechanisms of potential importance for canister failure. The developments made will form the basis for SKI's reviews and technical analyses of both generic and site specific assessments prepared by the Swedish nuclear industry as part of its R and D and site selection programmes. (author)