Chubu Electric May Have Underestimated N-Plant Quake Risks

Nagoya, Jan. 5 (Jiji Press)–Chubu Electric Power Co. may have presented data underestimating earthquake risks for a regulatory process to check whether its Hamaoka nuclear power plant in central Japan meets new safety standards, President Kingo Hayashi said Monday. Chubu Electric suspects that the estimated maximum seismic ground motion the power plant could experience may have been underestimated. The company will set up a third-party committee comprising external lawyers to investigate the matter. Last month, the Nuclear Regulation Authority stopped the regulatory screening for the plant in Omaezaki, Shizuoka Prefecture, following a report from Chubu Electric. The company has become unable to resume operations of any of the reactors at the plant anytime soon. Hayashi told a news conference in the central Japan city of Nagoya, where the company is headquartered, that the possible negligence “could have a serious impact on the NRA’s examination,” as well as “undermine trust in our nuclear power business and shake the foundations of our operations.” On Monday, the industry ministry ordered the company to report on the matter based on the electricity business law. Between 2014 and 2015, Chubu Electric applied for NRA screening for the plant’s No. 3 and No. 4 reactors. In September 2023, the NRA broadly approved the company’s assumption that the maximum seismic ground motion would be 1,200 gal. The company said Monday that it had explained to the regulatory watchdog that it adopted a method in which the average value of multiple seismic waves calculated under different conditions was taken as the representative wave. But before 2018, the company began using a different method. From around 2018, it intentionally designated a seismic wave different from the average value as the representative wave. The practice involved some employees at the company’s division for nuclear plant engineering, according to the company. As a result of the practice, the maximum seismic ground motion may have been underestimated. “I think they wanted to make the seismic ground motion value smaller,” said Tetsuya Toyoda, a key official responsible for the company’s nuclear business. In May last year or later, the company started an in-house probe after being requested by the NRA to show how it calculated the maximum seismic ground motion. Last month, it reported the practice in question to the NRA. Last November, the company said that it had not formalized contracts or completed payment procedures for part of safety improvement work at the Hamaoka plant. Executive Vice President Ichiro Ihara and others resigned to take responsibility. END [Copyright The Jiji Press, Ltd.]