Geological Disposal of Carbon Dioxide and Radioactive Waste in the Geotectonically Active Country of Japan

Abstract

In Japan, site selection for geological disposal of radioactive waste (RW) and carbon dioxide (CO2) is very important because of the large regional differences in tectonic activity. Assessment of the long-term stability of geological environments is key to geological RW disposal in Japan. A comprehensive system of long-term prediction of crustal movement and the groundwater regime around the virtual RW disposal sites has been developed in Japan. CO2 is naturally abundant, but geological disposal of the gigantic volumes of CO2 may have big impacts on the environment. One of the adverse effects of underground fluid injection is that it may induce earthquakes. Underground carbon microbubble injection accelerates advanced geological disposal mechanisms. The autogenously sealed ‘CO2 capsules’ can be formed in large basaltic sheets, ophiolite complex and oceanic crust. Sub-seabed aquifers under the deep sea floor can provide very safe and virtually limitless CO2 disposal. Different disposal strategies for CO2 and RW are needed because of the extreme difference in their toxicity and volume. The dispersion and dilution principle is possible for the CO2 disposal, while RW is strictly contained by the multiple barrier system. The stability of the geological environment is important for both CO2 and RW disposal.