Key Issues Identified From Project TRU-2 on the Generic Co-Location Concept of Transuranic (TRU) Waste and High-Level Radioactive Waste (HLW) Repositories in Japan

The Federation of the Electric Power Companies of Japan (FEPC) and the Japan Atomic Energy Agency (JAEA) have been collaborating with relevant organisations to promote the safe geological disposal of transuranic (TRU) waste following the already established disposal policy for high-level radioactive waste (HLW) in Japan. A result of this intensive collaborative effort was the production of a recent progress report (TRU-2) which describes the generic R&D for TRU-waste disposal in Japan. In order to improve feasibility and reduce costs and the burden on siting, the concept of co-locating TRU-waste and HLW repositories in a single complex was assessed in detail and compared with the results from several other countries that have also looked at co-location disposal. Heat from HLW, high pH plume(s) from the large amounts of cementitious materials used in the engineered barrier system (EBS) of TRU waste, and nitrates and organic materials in certain types of TRU waste were identified as critical reciprocal influences that might degrade the performance of the TRU/HLW co-location disposal system over the long-term. It was shown that these reciprocal influences could be avoided by establishing a separation distance between the two repositories of approximately 300 meters.