Current status of the geological disposal programme and an overview of the safety case at the pre-siting stage in Japan

Abstract

In Japan, high-level radioactive waste and specific low-level radioactive waste which includes long-lived radionuclides are planned to be disposed of in the geological formations at depths greater than 300 ​m. The disposal site will be selected through a stepwise site investigation process that consists of a Literature Survey, Preliminary Investigation, and Detailed Investigation phases. In October 2020 a Literature Survey was launched in Japan at two municipalities in Hokkaido for the first time since NUMO initiated a nationwide call for volunteer municipalities in 2002, and the outcomes are currently being compiled. To enhance the public’s understanding of how to implement safe geological disposal in Japan based on the latest scientific knowledge and technology, NUMO, as the implementing organisation, developed and published a safety case for geological disposal at the pre-siting stage. This safety case provides multiple lines of arguments and evidence to demonstrate the feasibility of the geological disposal and a basic structure for a safety case that will be applicable to any potential sites in Japan. The safety case also presented some R&D challenges to enhance the technical confidence of the project, including the R&D topics related to rock mechanics. This report presents the current status of the geological disposal programme in Japan, together with the status of the Literature Survey phase and an overview of the NUMO safety case.