Chubu Electric Pulls Hamaoka Restart Applications After Its Own Seismic Data Turns Out to Be Rigged

Chubu Electric Power is walking away from its bid to restart two reactors at Hamaoka Nuclear Power Station after its own investigators concluded the seismic data underpinning the safety case cannot be trusted. The utility told the Tokyo Stock Exchange on September 14 that an extraordinary board meeting had voted to withdraw the reactor installation change permits for Units 3 and 4, along with a related construction-plan approval and safety-regulation change filing, all submitted under Japan's post-Fukushima regulatory standard. Chubu said it will resubmit "once preparations are complete" but gave no timetable, and said the hit to this year's and future group earnings "remains undetermined".

The trigger was a report handed to the board on September 11 by an independent committee investigating how Chubu calculated the plant's "standard seismic ground motion," the baseline shake the reactors must be engineered to survive. Chubu had told the Nuclear Regulation Authority it picked each representative earthquake waveform because it was closest to the average of 20 randomly generated simulations. Investigators found that in at least 105 of 225 waveform cases, engineers instead generated many candidate sets of 20 simulations and picked whichever set produced the reading they wanted; in at least seven further cases, staff deliberately chose a wave that didn't match the average, then reverse-engineered the other 19 waveforms afterward so the paperwork would show a match. Investigators also found the company fabricated supporting calculations after the fact, using several distinct techniques, to make earlier manipulations look statistically clean. Some of the pressure traced to a local fault, called A-17, that Chubu had told regulators was not active until the NRA repeatedly pushed back, forcing a stricter, more time-consuming reassessment the company was racing to finish.

Chubu only admitted the problem after the NRA came asking questions in May 2025, requested the underlying contractor reports that October, and confronted the company with data its explanations couldn't square. Chubu confirmed the manipulation internally in December 2025, disclosed it publicly on January 5, and has been under NRA regulatory inspection since January 26. In the redacted report Chubu released alongside the withdrawal notice, the committee said it would not simply brand the conduct "falsification" or "data fraud," but was equally clear it found nothing "appropriate" about it, and cautioned that 77 of the 225 cases still need further work before their status can even be confirmed.

The fallout reaches the top of the company. President Kingo Hayashi and chairman Satoru Katsuno both step down on September 30 and move into advisory roles; they are replaced from October 1 by Minoru Yasui, currently a director and senior executive officer whose career has run mainly through thermal power and energy-business management. Chubu said the change was needed "to clarify management responsibility and pursue reform under a new structure," citing the September 11 report directly.

For a utility whose financing and capacity planning have long assumed Hamaoka would eventually restart, the withdrawal removes that assumption without supplying a replacement date. Chubu says a fuller account will follow once the independent committee's broader findings are digested; for now, investors are left with 77 unclassified waveform cases and no restart timeline.