Japan's NRA calls JAPC president to appear after finding Tsuruga-2 reactor not meeting regulatory standards

Commissioners at Japan's Nuclear Regulation Authority decided at a meeting July 31 to call Japan Atomic Power Co. President Mamoru Muramatsu to appear at a NRA meeting following the JAPC's intention to revise its application on restart of the 1,160-MW Tsuruga-2 pressurized water reactor.

The move followed a July 26 recommended finding presented by the regulator's secretariat that JAPC's Tsuruga-2 nuclear reactor does not conform with Japanese regulatory standards because of difficulty over denying the possibility of a seismic fault underneath the reactor building that could become active in the future.

Should the NRA accept the recommended finding, it would represent the first instance to effectively reject a restart application for a reactor since Japan's current system of nuclear regulation came into effect in 2012 following the 2011 Great East Japan Earthquake and the subsequent nuclear crisis in Fukushima in the northeast.

Any NRA rejection for restart of the Tsuruga-2 reactor could have a greater implication for Japan's Green Transformation policy, under which it has placed nuclear power as among key decarbonization steps to be used upon a safety assurance from the NRA.

Following the NRA's recommended finding, the JAPC said in a statement July 26 that it will continue its efforts to restart the Tsuruga-2 reactor by undertaking additional research and expand its evidence to support the case.

Key issue

A seismic fault codenamed K runs beneath Tsuruga-2 and has been a key issue since the JAPC filed an application with the NRA in 2015 to demonstrate the unit's compliance with regulatory safety requirements.

The NRA requires important equipment, including reactor buildings, to not be located on an active seismic fault where an earthquake has occurred during the past 130,000 years.

According to the JAPC data, five relatively short seismic faults, including K, exist on the Tsuruga plant site. However, it argued at NRA review sessions that the K seismic fault was formed more than 130,000 years ago.

The extended Tsuruga-2 review process has been further complicated by errors in documentation submitted by the JAPC. The NRA halted its Tsuruga-2 review for about two years from 2020 until Dec. 8, 2022, after its reviewers found more than 1,000 errors in JAPC safety documents.

The JAPC in April 2023 was then given until Aug. 31, 2023, to resubmit documentation with the errors corrected.

"Given this situation, with so many errors, we simply cannot continue our review work," NRA Commissioner Akira Ishiwatari, who at the time was in charge of natural hazards for NRA, said during an April 5, 2023, NRA Commissioners meeting.

Commissioners at that 2023 meeting set an Aug. 31, 2023, deadline for the JAPC to resubmit its Tsuruga-2 data. The resubmitted documentation formed part of the case on which NRA made its decision July 31.