On March 3, 2026, the Ministry of Economy, Trade and Industry (METI) made a request to Ogasawara Village in Tokyo to accept the implementation of a literature survey in Minamitorishima Island for the selection of a final disposal site for high-level radioactive waste. Indeed, Minamitorishima Island is considered to be one of the areas which is least prone to earthquake and volcanic activity in Japan, being positioned sufficiently far away from plate boundaries on the Pacific Plate. It is therefore true that multiple experts have suggested that Minamitorishima is the most promising candidate location for a geological disposal site for high-level radioactive waste from the perspective of geological safety. However, very little literature exists on the geology of Minamitorishima.<\/p>\n
Apart from the effects of earthquake and volcanic activity, there are also many factors that must be taken into consideration in order to safely implement geological disposal. METI and the disposal operator, the Nuclear Waste Management Organization of Japan (NUMO) plan to hold briefings for residents on Chichijima Island and Hahajima Island in Ogasawara Village on March 14 and 15. [i ] We would like to point out several issues that should be taken into consideration regarding geological disposal at Minamitorishima before determining whether or not to conduct a literature survey.<\/p>\n
Minamitorishima is approximately 1.5 km2<\/sup>\u00a0<\/sub>in area. The above-ground facilities for the disposal site require 1 to 2 km2<\/sup>. Is there enough space to store the excavated soil safely? Further, does the island meet the conditions for building a dedicated port for transporting high-level radioactive waste? Procuring the fresh water and gravel required for making concrete locally on the island would also seem to be difficult. In addition, Minamitorishima has a low elevation. This poses the risk of the flooding of facilities during high tides and other events. Constructing ground facilities which can withstand salt and typhoon damage under these adverse conditions also poses significant challenges.<\/p>\n The underground facilities require an area of 6~10 km2<\/sup>. Minamitorishima is a coral island formed on a submarine volcano. The island\u2019s shallow subsurface bedrock consists of limestone, which is porous and has a low water shielding capacity. If a large influx of ground water containing seawater occurred, ensuring safety during excavation and maintaining the stability of the shaft would be a very arduous task. In the first place, the water surrounding the island is very deep, and there still remains a question concerning whether or not there is sufficient space to build the underground facilities.<\/p>\n Minamitorishima is located approximately 2,200km from the Japan Atomic Power Company\u2019s Rokkasho Reprocessing Plant (Aomori Prefecture), where the vitrified waste is produced. Long-distance transportation increases the risk of accidents and damage caused by typhoons and tsunami. The International Atomic Energy Agency (IAEA) Regulations for the Safe Transport of Radioactive Material have established the principle of radiation protection that states, \u201cProtection and safety shall be optimized in order that the magnitude of individual doses, the number of persons exposed and the likelihood of incurring exposure shall be kept as low as reasonably achievable, economic and social factors being taken into account, within the restriction that the doses to individuals are subject to dose constraints.\u201d This includes the \u201cnormal exposure\u201d associated with routine transport operations and \u201cpotential exposure\u201d that considers the probability of accidents or operational errors. Long-distance transport through regions with harsh meteorological and oceanographic conditions, combined with the high frequency of shipments, does not comply with this principle of radiation protection.<\/p>\n If the currently considered method, disposal of waste 300m to 500m underground, is found to be too demanding, the method called Deep Borehole Disposal, which is the disposal of radioactive waste in an ultra-deep borehole with a depth of several to 10km, could be a potential alternative method. However, the only method currently prescribed by law is geological disposal, and if this deep borehole method is adopted, it will be necessary to revise the law. Furthermore, Deep Borehole Disposal is a technology still in the research and development stage, and its feasibility is not yet guaranteed. The research is expected to require a considerable amount of time before actualization is possible.<\/p>\n Sea level rise due to global warming will certainly continue to occur. According to the Intergovernmental Panel on Climate Change (IPCC), by the end of 21st century (on average 2081-2100), the sea level around Japan is projected to rise 0.40 m (0.30-0.55 m) under a 2\u00b0C warming scenario (SSP5-8.5), and 0.68 m (0.56-0.88 m) under a 4\u00b0C warming scenario. Moreover, if large-scale collapses of the Atlantic and Greenland Ice Sheets occur, the possibility of a global sea level rise of 2m by 2100 and 5m by 2150 cannot be ruled out. [ii]<\/p>\n Minamitorishima is a small, flat island with maximum elevation of about 9m above sea level. Even if it does not submerge during sea level rise, the risk of flooding during high tides will increase significantly.<\/p>\n All the adverse conditions mentioned above will ultimately be reflected in the disposal cost. According to NUMO, disposal costs are estimated to be approximately 4 trillion yen, but it would seem that further increases in costs are unavoidable.<\/p>\n Calls for the government to take responsibility for pushing forward with the selection of disposal sites have certainly been increasing. However, as far as we can confirm from the briefing materials, the government\u2019s request for a literature survey does not provide sufficient information on these matters.<\/p>\n The government approach of selecting a remote, uninhabited island, seeking loopholes in the requirement for residents\u2019 consent, diminishes public interest in the high-level radioactive waste issue. Regarding the selection of a final disposal site, the challenge of removing the vitrified high-level radioactive waste returned from overseas out of Aomori Prefecture by 2045 is becoming urgent. Proceeding with the Minamitorishima proposal, which is expected to pose significant challenges in implementation, could result in a further delay in resolving fundamental problems.<\/p>\n [All links in Japanese]<\/p>\n \u00a0[i]\u00a0 www.numo.or.jp\/topics\/202526030314.html<\/a><\/p>\n\n
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