Interface Issues Between Storage Safety and Post-Storage Transport Safety in Japan. Annex V

In Japan, interim storage facility using dual–purpose casks (metallic dry casks for storage and transport) will be in operation within a couple of years. These dual-purpose casks are currently planned to be transported to the reprocessing facility after the long term storage (assumed to be the period of 40-60 years) without any direct inspection of their contents, which needs to open the cask lid. Therefore, interface issues between the long term storage and the post-storage transport safety are becoming especially important. Major part of these interface issues is the integrity of such safety functions as containment, prevention of criticality, radiation shielding and decay heat removal during storage period. To ensure the integrity of safety functions for the long term storage, it is important to understand degradation phenomena by aging effects which will be expected to metallic casks and spent fuel and to consider adequately them in the safety evaluation of the interim storage facility for the long term storage and post-storage transport. Japan Nuclear Energy Safety Organization(JNES), which is the Technical Support Organization(TSO) for Japanese government (Nuclear and Industrial Safety Agency), has extracted expected degradation phenomena by aging effects' and has carried out various tests and evaluation, including corrosion test of metallic cask materials, material test for basket and neutron shielding material, metallic cask lid leak test (including full scale mock-up cask drop test), simulated thermal test for metallic cask, spent fuel cladding integrity test. In addition, PWR spent fuel experimental storage test is currently planned. However, in this paper, summary of following 3 items are reported: • Metallic cask lid leak test (including full scale mock-up cask drop test); • Spent fuel cladding integrity test; • PWR spent fuel experimental storage test (long term test plan)