Safety strategy of geological disposal of high level radioactive waste

High-level radioactive waste generated through nuclear power generation retains radioactivity for a long period such as tens of thousands of years or more. As a permanent disposal method for such radioactive waste, "geological disposal," where the waste is buried deep underground to isolate and confine it from human living environment for more than tens of thousands of years, has been selected internationally. In Japan, the project is being promoted with the aim of realizing geological disposal. In order to ensure the safety of geological disposal, it is important to perform the careful investigation and evaluation of the geological environment for candidate sites, as well as the design of the disposal site with safety margin. In addition, it is important to evaluate the radiation effects on humans for tens of thousands of years in future, while taking uncertainty into consideration. In particular, in Japan, which is located in a mobile belt where volcanoes, faults, and seismic activities are active, it is essential to consider the effects of these natural phenomena. This report outlines the concept of safety ensuring against such geological disposal. (A.O.)