Report on the 2nd Meeting of the Geological Disposal Technical WG: Experts Against Geological Disposal Attend a Government Working Group

By Takano Satoshi (CNIC)

The second meeting of the Geological Disposal Technical Working Group (Technical WG), a working group of the Ministry of Economy, Trade and Industry (METI), was held on March 29. At present, drafts of reports of the literature surveys underway in Suttsu Town and Kamoenai Village in Hokkaido for high-level radioactive waste disposal sites are under discussion in this WG. The first meeting was held on February 13, and after broadly confirming the outline of the process and points to be discussed, full-fledged discussions have begun since the second meeting.

The members of the WG are experts recommended by academic societies related to geological disposal, but there are no experts in the WG who are negative about the implementation of geological disposal in Japan. Under this circumstance, three experts in the field of geology attended the second Technical WG to give statements from the standpoint that geological disposal in Japan is impossible at the current level of science and technology. I would like to review the history of this unusual situation.

It all started with the second meeting of the Subcommittee on Specified Radioactive Waste held on December 11, 2023. A statement that, according to a METI document, was issued on October 30, 2023 was presented to the subcommittee, the parent committee of the Technical WG. In the statement, supported by more than 300 people, geological researchers expressed the view that “There is no suitable place for geological disposal in Japan, one of the world’s most tectonically active zones”¹⁾. At the second subcommittee meeting, members of the committee agreed that the content of the statement should be thoroughly discussed, and it was decided to task out (assign duties) to the Technical WG, where there is a large proportion of technical experts.

After this was decided, CNIC released an “Expert Opinion to the Geological Disposal Technical WG” on February 22, 2024. We suggested that when the Technical WG discussed the statement, the authors of the statement should attend to give evidence and participate in the discussion to ensure fairness and transparency²⁾. As well as the content of the expert opinion, the Technical WG was also requested to reflect the latest findings on the mechanism of the January 1, 2024 Noto Peninsula earthquake as related to the safety of geological disposal.

As I serve as a member of the subcommittee, from my position as a member of the parent committee of the Technical WG, I submitted a written opinion with similar content to the expert opinion to METI and the chairperson of the Technical WG.

The reason why the authors of the statement were able to participate in the second meeting of the Technical WG was probably because this written opinion was adopted. The authors invited were Okamura Satoshi, Professor Emeritus of Hokkaido University of Education; Ono Yugo, Professor Emeritus of Hokkaido University, and Akai Junji, Professor Emeritus of Niigata University.

Professor Okamura firstly gave a 15-minute presentation. Touching on the differences in geological characteristics between the Japanese archipelago and Finland, Professor Okamura pointed out that the Scandinavian Peninsula, which has not experienced tectonic movements for over one billion years, and the Japanese archipelago, which is in one of the world’s most tectonically active zones, have totally different geological conditions.

Professor Okamura then explained the bedrock characteristics of Suttsu Town and Kamoenai Village. Much of this area consists of water-cooled fractured rock from a Neogene submarine eruption about 10 million years ago and is unsuitable for geological disposal due to the heterogeneous nature of the bedrock. Even if a borehole exploration is carried out in the outline survey, it is difficult to grasp the spatial extent of the heterogeneous bedrock, and it is therefore impossible to avoid bedrock of a low-strength and high water permeability.

Problems regarding active faults were also raised from a number of viewpoints. Severe inland earthquakes often occur in places where active faults have not been identified. The Kumamoto Earthquake in 2016 and the Eastern Iburi Earthquake that occurred in Hokkaido in 2018 fall into this category. In addition, earthquakes originating from deep fluids (hydrothermal or magmatic) and the possibility of linkage with active fault zones were also pointed out. In the January 1 Noto Peninsula earthquake, it is surmised that the rise of deep fluids several tens of kilometers below the surface caused a swarm of earthquakes, which destroyed faults and were linked to an active fault zone of 150 kilometers, which was far longer than forecast.

The Noto Peninsula earthquake also raised questions regarding the methods of recognition of offshore active faults. Thus far, the identification of offshore active faults has relied mainly on acoustic exploration to survey underground conditions by emitting sound waves from ships and scrutinizing the waveforms. However, experts in tectonic geomorphology, who investigate the existence of faults from the topography of the seabed, have pointed out the existence of larger numbers of long faults in offshore areas of the Noto Peninsula. It can be said that the Noto Peninsula earthquake has clearly confirmed the limitations of acoustic exploration and the effectiveness of tectonic geomorphological methods.

In light of these new findings on active faults, the danger of the Kuromatsunai Lowland fault zone, which exists from Suttsu Town to Kuromatsunai Town in the south, also becomes clear. This is because low-frequency earthquakes, which are believed to indicate the presence of deep fluid, have been confirmed several times even 30 km below the surface of Suttsu Town. As the energy level is not as great as that of the Noto Peninsula, there is no immediate likelihood of a large earthquake occurring, but the mechanism of earthquakes caused by deep fluid and their linkage to active faults is similar to that of the Noto Peninsula. However, it was pointed out that the evaluation criteria of the current literature survey only provide a one-sided evaluation limited to the possibility of new volcanoes.

After Professor Okamura’s presentation, METI and the organization responsible for the literature survey, the Nuclear Waste Management Organization of Japan (NUMO), offered a rebuttal. The Technical WG is supposed to be a forum where each committee member takes the initiative in discussing issues, but I was surprised by the overly defensive stance of the government and NUMO in presenting a rebuttal before discussions with committee members began.

Firstly, regarding the differences in geological characteristics between the Japanese archipelago and the Scandinavian Peninsula, METI explained that areas where fault activity and volcanic activity occur in Japan, a tectonically active zone, have changed little, such areas should be avoided.

Secondly, regarding various points about earthquakes, METI first stated that the impact of earthquake tremors would be limited. This is because vitrified high-level radioactive waste would shake in unison with the surrounding bedrock, and because deep underground tremors are smaller than those at the surface. METI added that geological disposal facilities will be designed to be earthquake resistant. It was also explained that the investigation of the impact of unidentified active faults will be carried out during or after the outline survey.

METI also argued that the Japan Nuclear Regulation Authority (NRA) gives a comprehensive assessment of the existence of active faults through tectonic geomorphological, geological, and geophysical surveys in its review guide. The ministry further noted that it would consider low-frequency earthquakes originating from deep fluids, including, if necessary, the possibility of reflecting this aspect in the thinking on the evaluation of geological disposal surveys.

NUMO then explained the bedrock characteristics of Suttsu Town and Kamoenai Village. NUMO stated that the values for water permeability and strength of rock deeper than 300 m have not been obtained, and that it was therefore impossible to make judgments. Apart from that, NUMO’s answers were the same as those given by METI. Rather than face the questions head-on, METI and NUMO’s responses conspicuously avoided the essential arguments by, for example, shifting or blurring the points, or saying that they would clarify the situation during the next or subsequent phases of the investigation.

Committee members were then allowed to make comments but these were limited to just two minutes each. Some comments showed superficial sympathy for Professor Okamura’s presentation, but the opinion of many of the committee members was that the points and questions raised should be confirmed and resolved at the next stage of the investigation. It is hard to say that active discussions took place, as the attitude of many of the committee members seemed to be to toe the METI and NUMO line.

At the same time, a few committee members expressed opinions such as “One member of the committee said that geological disposal could proceed because it can be reversed at any time, but I disagree. We need to show very definitively whether we are able to judge significant future diastrophism (crustal deformations),” and “I think it is true to say that deep fluids, low-frequency earthquakes, and fault activity will not be cleared away even if the literature survey proceeds to an outline survey and then to a detailed survey.”

In the end, deliberation on the statement ended in about an hour. The participation of experts opposed to geological disposal in the discussion was, to a certain extent, worthwhile. On the other hand, there was too little time for a serious scientific discussion, and there were problems with the handling of the proceedings. In order to avoid use of this discussion as an alibi for the government, which wishes to say it “has listened to the voices of opposing experts,” it is hoped that there will be protests and demands from civil society to “engage in deeper discussion” and “not let the topic end with just this meeting.”

1) The statement can be seen at the following address (in Japanese)

cnic.jp/wp/wp-content/uploads/2023/11/902f6cbc42a46268054c87533439491b.pdf

2) The expert opinion can be seen at the following address (in Japanese)

【地層処分技術WG への提言】「声明」の呼びかけ人を参考人として技術WGの議論に参加させよ