Japan's current research emphasizes the generic validation of geologic disposal and general survey of geologic environment of the Japanese islands. Understanding geologic setting is essential to the assessment of longterm safety of radioactive waste disposal. Scenarios for safety assessment of high level waste disposal should include even natural events of very low probability and very slow geologic processes.
Geologic predictions should be based on extrapolation, natural analog, probability, experiments, conceptual model, numerical simulation and safety-assessment model. The geologic environment at the depth of several hundreds and some 1, 000 meters should be clarified to predict the fate of buried radioactive waste. In situ experiments are planned for the examination of validity of long-term isolation system of high level waste.
Long-term stability of the geologic environment is of primary importance in disposal of radioactive waste in Japan. The nature and behavior of deep groundwater provide key to the modeling and quantitative evaluation of performance of high-level waste isolation system.