Chubu Electric Suspected of N-Plant Data Fraud Cover-Up

Tokyo, July 1 (Jiji Press)–Chubu Electric Power Co. overwrote data after a regulatory investigation into its earthquake risk data fraud involving its Hamaoka nuclear power plant in Shizuoka Prefecture, central Japan, the secretariat of the Nuclear Regulation Authority said Wednesday. “We suspect there was a cover-up,” NRA Chairman Shinsuke Yamanaka told a press conference. The nuclear watchdog instructed its secretariat to investigate whether Chubu Electric executives were involved in the matter. It plans to decide its response to the scandal as early as this summer, after confirming the details. “We take it extremely seriously and apologize again from the bottom of our hearts,” the company said in a statement. Chubu Electric used a method different from what was reported to the NRA to estimate a maximum seismic ground motion that the plant could experience, during the nuclear watchdog’s safety screenings crucial for the restart of the plant’s No. 3 and No. 4 reactors. The company allegedly underestimated the maximum seismic ground motion, by selecting favorable data while suggesting that the figures came from proper calculation. Such irregularities are believed to have been carried out across multiple departments. The NRA secretariat said Chubu Electric retroactively collected and rewrote data linked to the cherry-picking after it began hearings over the scandal in May last year, affecting 69 of the 225 sets of data being investigated. The power utility told the nuclear watchdog that it had randomly collected 20 seismic wave data points and selected data close to the average for the NRA screening, when it had actually asked a contractor to select data favorable to the company from more than 1,000 data points. In some cases, the cherry-picking involved nearly 30,000 data points. “I feel there was malicious intent,” Yamanaka said. Assuming a lower maximum seismic ground motion could reduce earthquake-proofing costs for plant facilities and shorten construction periods. The company applied for NRA screenings of the No. 3 and No. 4 reactors between 2014 and 2015. In 2023, the NRA broadly approved the company’s assumption for the maximum seismic ground motion. The NRA became aware of the data fraud through an external tip off in February 2025. Chubu Electric made public the misconduct in January this year, setting up a third-party committee to investigate the matter. END [Copyright The Jiji Press, Ltd.]