Development of grout materials for a geological disposal system for high-level radioactive waste

Fukuoka, Naomi; Shinkai, Fumiaki; Miura, Norihiko*; Nobuto, Jun*; Yamada, Tsutomu*; Naito, Morimasa 

High-level radioactive waste management in Japan is based on the multi-barrier concept, composed of the engineered barrier system and the surrounding geological formations. Although cementitious materials are commonly used for rock support, lining, and grouting, their pH plume are considered to have an adverse effect on long-term safety of a geological disposal system. In addition, during the emplacement of waste package with buffer material, it is required to limit amount of groundwater inflow into a disposal pit or tunnel to a certain level by grouting because the bentonite clay buffer is easy to swell in time by contact with the groundwater. Therefore, it is necessary to develop new grout materials with penetrability for smaller fractures. This report shows the most appropriate composition of new grout materials to be suitable for the in-situ experiment based on the result of indoor test.