Overview of the NUMO safety case at pre-siting stage

NUMO has developed a safety case for geological disposal at pre-siting state in Japan. This safety case provides the multiple lines of arguments and evidence to demonstrate the feasibility and safety of geological disposal, which will encourage stakeholder confidence in the safe implementation of geological disposal and will provide a basic structure for a safety case which will be applicable to any potential site. This paper will provide a brief overview and approach of this safety case, emphasizing practical approaches and methodology which will be applicable for the conditions/constrains during an actual siting process. The geological environments of various potential host rocks are developed as site descriptive models, which are, as realistically as possible, based on the current best understanding of Japanese geology. A rigorous and flexible methodology for tailoring repository design to site descriptive models has been developed. Safety assessment models and data also have been developed and applied for demonstration of the technical basis of the safety assessment. (author)