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Chubu Electric continued data misrepresentation on quake risk after regulator probe began
The company used an alternate calculation method that produced lower seismic estimates than those submitted to the Nuclear Regulation Authority. The practice continued after hearings opened in May 2025 and affected 69 of 225 data sets under review.
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Chubu Electric Power Co. continued to submit seismic data calculated by a method different from the one reported to the Nuclear Regulation Authority after the regulator began hearings on the issue in May 2025. The secretariat of the authority disclosed the findings Wednesday after completing an on-site inspection at the Hamaoka nuclear power plant in Shizuoka Prefecture.
The company selected favorable data while presenting the figures as the result of the required calculation, according to the secretariat.
Background of the screenings Chubu Electric applied for safety screenings of the plant's No. 3 and No. 4 reactors between 2014 and 2015. The authority broadly approved the company's maximum seismic ground motion assumptions in 2023. The authority learned of the data issue through an external tip in February 2025.
Chubu Electric disclosed the misconduct in January 2026 and established a third-party committee to investigate.
Inspection findings and next steps The on-site inspection found that almost no records were kept from the period when the maximum seismic ground motion figures were established. The authority will decide whether to withdraw its 2023 approval after reviewing the third-party committee report. Chairman Shinsuke Yamanaka stated that withdrawal remains possible because of the misconduct.
