Research for developing the scientific basis to ensure the safety of the radioactive waste disposal. Geological disposal and intermediate disposal for radioactive waste

Geological disposal is to dispose high-level radioactive waste alone or in parallel with long half-life low-exothermic radioactive waste containing trans-uranium elements with high radioactivity level (TRU waste) to the depth of 300 m or deeper underground. The concept of intermediate disposal is to dispose reactor internal structures and radioactive metals such as fuel cladding pipes and control rods that were generated along with the decommissioning of aged nuclear power plants, having lower radioactivity than high-level radioactive waste but still having high radiation, to an assumed depth of about 100 m. Recent movements concerning the disposal of radioactive waste disposal include the 'Scientific Characteristic Map' relating to the geological disposal of high-level radioactive waste published in July 2017 by the Agency for Natural Resources and Energy. As a research and development system relating to the disposal of radioactive waste, the Japan Atomic Energy Agency is conducting survey and research using a 500 m depth tunnel at Tono and a 380 m depth tunnel at Horonobe. As a safety regulation support research for geological disposal / intermediate disposal, the following studies were performed in 2017: (1) research on evaluation method concerning erosion speed and upheaval speed, (2) examination of fault activity evaluation method based on mechanical index, and (3) study on the groundwater flow evaluation method under low penetration environment. As a future hydrological science theme, it is necessary to consider the evaluation and modeling of the groundwater flow system based on the influence of sea level fluctuation in the coastal area. (A.O.)