Japan Approves Adjusted Tsunami Height Assessment for Genkai Nuclear Power Plant

At its regular meeting held on September 2, Japan's Nuclear Regulation Authority (NRA) formally approved Kyushu Electric Power Co.'s assessment of the maximum potential tsunami height at the Genkai Nuclear Power Plant site in Saga Prefecture. Under this adjustment, the maximum tsunami height on the northwest side of the Genkai plant site has been raised to 14 meters; previously, the maximum tsunami height on the north side of the site was 6 meters.

The NRA determined that the ground surface on the northwest side of the Genkai plant site is covered by bedrock with an elevation of 16 meters, and therefore no additional disaster prevention measures are required even under the new tsunami height assessment. In July, the NRA had already approved the review report draft submitted by Kyushu Electric Power and confirmed that the assessment complies with the new regulatory standards. Subsequently, no objections were raised during consultations with the Minister of Economy, Trade and Industry and other relevant parties.

This assessment adjustment stems from the long-term evaluation report on active faults in the southwestern Sea of Japan released in 2022 by the Headquarters for Earthquake Research Promotion. In its assessment, Kyushu Electric Power considered a scenario in which an active fault located approximately 100 kilometers northwest of the Genkai plant could move in conjunction with another active fault.

Regarding seismic resistance, the design-basis earthquake ground motion intensity used as the basis for seismic design did not exceed existing levels, and therefore no changes were made this time. Units 3 and 4 of the Genkai Nuclear Power Plant had previously passed relevant reviews and resumed operation in 2018.