The Long-term stability of geological environments in the various rock types in Japan from the perspective of uranium mineralization

Sasao, Eiji   

Long-term stability of the geological environment is one of the important keys for geological disposal of high-level radioactive waste in the Japanese Islands due to their location in a tectonically active island-arc. Uranium occurrences in Japan have been subjected to many geological processes inherent to the island-arc setting. Mode of occurrence of the uranium mineralization can be instructive as these could provide useful information on the long-term stability of the geological environment. Uranium mineralization is mainly in Tertiary sedimentary rocks and granitic rocks and less commonly in Cretaceous and Paleo/Mesozoic sedimentary sequences or metamorphic rocks. A variety of rocks host the Japanese uranium mineralization suggesting that geological environments suitable for geological isolation are widely distributed in the Japanese Islands, despite their location in a geologically active area. This effort will support building confidence in deep geological disposal.