Design Options for HLW Repository Operation Technology: Part I—Demonstration and Evaluation of Remote Handling Technologies

The long-term safety of a geological repository for high-level radioactive waste (HLW) in Japan is achieved using a multi-barrier system, with emphasis on an engineered barrier system (EBS) consisting of bentonite-based buffer material and a steel overpack containing vitrified wastes. Providing a wide variety of technical options for repository operation, which can allow EBS construction under various repository conditions, is valuable for the volunteering approach to siting a HLW repository in Japan. In order to confirm technological applicability of candidate techniques and to evaluate compatibility in an operation system, full-scale tests of various remote-handling and-emplacement techniques for the EBS were conducted. The test results are summarized in the technical menu which is hierarchical structured database. Since the long-term performance of EBS is significantly influenced by remote handling and emplacement techniques for EBS, consistency of the operation technology must be evaluated from the view point of system standing. In this program, evaluation methodology was studied and several indexes, representing requirements for the repository operation and management, were identified. Indices include current technical availability, long-term safety of the resultant EBS, operational safety, engineering reliability, retrievability, etc., with expert assessment complementing a more quantitative evaluation.