Geological Disposal of High-level Radioactive Waste and Site Characterization Techniques

摘要

To finally select a disposal site for high-level radioactive waste and to build an appropriate repository system there, it is first necessary to characterize the geological environment at the site. Before an underground investigation facility is finally constructed, field investigations are to consist mainly of aerial and surface-based geophysical investigations combined with borehole drilling. Even in the underground facility, borehole drilling from the tunnel walls and geophysical investigations may be fundamental methods for studying the geological environment. High-resolution geophysical information will be required to understand the geological structures around the tunnels (distribution of major water-conducting fractures etc.) and to characterize the excavation disturbed zone. The host rock is expected to function as a natural barrier in geological disposal. It is desirable, therefore, that site characterization should be carried out in such a way as to minimize the disturbance of the geological environment. From this point of view, the technology of geophysical investigations will play an important role in a future site characterization.