Radioactive Waste In Japan Research Articles

放射性廃棄物処分と地質問題

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.

Geological Disposal of High Level Radioactive Wastes in Japan and Earth Science

About one fourth of the total production of electricity in Japan was generated in nuclear power plants in 1985. Now, the disposal of radioactive wastes is a major environmental problem. The Japanese islands locate in the tectonically active zone around the Pacific Ocean. Four major lithospheric plates collide or scratch each other in or near Japan. Major earthquakes often shake the Japanese islands where active faults distribute densely. Eruption of volcanoes and hot springs indicate high geothermal activity.However, many observations indicate that shocks of earthquakes are much milder at the depth of some hundred meters than at the ground surface. Some areas even in Japan have been free from volcanic activities during the last tens of millions years.High density of fractures in rocks due to past tectonic disturbances are more serious problems for the isolation of radioactive wastes, as some of fractures might provide pathways for hazardous contaminated water. Major efforts should be paid to develop precise techniques which allow us three dimensional mapping of underground fractures with no hurt to rock body which provides the natural barrier against the migration of radionuclides.The long-term performance of the waste isolation system should be estimated adequately. The knowledge of recent tectonic activities (Quaternary tectonics) and the study of natural analogues provide a basis for long-term prediction of the stability of the burial site.