The third case study postclosure safety assessment for a hypothetical Canadian deep geologic repository

The Third Case Study is a post-closure safety assessment of the deep geologic repository concept for used CANDU fuel in the Canadian Shield. It incorporates advances in repository design concepts and in analysis methodology since the Environmental Impact Statement case studies presented in 1994 and 1996. The reference container has an outer copper shell for corrosion protection, an inner steel vessel for structural support, and a capacity to hold 324 used fuel bundles. These containers are emplaced in a horizontal in-room configuration and surrounded by dense bentonite based clay seals. The hypothetical geosphere was developed using a geostatistical approach. This paper presents an overview of the study. We conclude that the Third Case Study repository design and hypothetical site would meet international postclosure dose rate guidelines. (author)