Dry Interim Storage in Switzerland for 30 Years

Since Patram2010 long-term interim dry storage was introduced as a major issue to the international community. At the IAEA level several working groups have been found for short term, long term and extended dry storage. Raised issues as material degradation or transportability after the storage period are linked to dual purpose casks. Switzerland has started to store the first dual purpose cask 30 years ago. The paper addresses the history of this 30 year stored cask, the monitoring of leak tightness, temperature and dose as well as the performed transports during the last 30 years. The performance of this cask will be presented and discussed with respect to the development of cask design, contents and requirements. This analysis provides results, which can be helpful for decisions to be taken for casks stored later and faced with this situation during and after their long term storage period. The paper will also give a regulator’s perspective of the interim dry storage option considering current developments in the spent fuel domain using Switzerland as an example. Subjects as high burn-up, increased enrichment, MOX disposal, material degradation, fuel degradation or transportability after short and long term storage are discussed. Consequences for safety margins of dual purpose cask designs are highlighted.