Misconduct at Hamaoka Nuclear Plant: A Serious Situation Undermines Safety

Editorial

15:38 JST, January 7, 2026

The misconduct is a grave act of wrongdoing that could fundamentally overturn assessments over the safety of nuclear power plants. It surely raises concern about whether the moves to restart nuclear reactors across the country could be dampened.

Chubu Electric Power Co. announced that it may have used inappropriate data during the Nuclear Regulation Authority’s safety screenings for restarting nuclear reactors at its Hamaoka nuclear power plant. The electric company said there is a possibility that it had underestimated the projected maximum tremors of an earthquake that could affect the Hamaoka reactors.

Calculating the expected seismic shaking and tsunami height is the starting point for safety screenings. Based on this, the screenings had proceeded to assess whether the plant’s buildings and facilities could withstand the shaking, but now the premise has collapsed.

Redoing the screenings is unavoidable, pushing the restart of the reactors further into the future. Chubu Electric’s president himself stated, “This is a case that could shake the very foundation of our business.” It is an extremely grave situation that must be taken seriously.

According to Chubu Electric, personnel in charge in the nuclear sector intentionally selected data favorable to the company’s estimations about the shaking from an earthquake and explained the matter to the nuclear regulator.

It is difficult to understand how Chubu Electric could have thought that such an arbitrary method would go unnoticed. The misconduct came to light in February last year when the nuclear regulator received information that indicated that there were “irregularities.”

Regarding the Hamaoka nuclear power plant, wrongdoing in the procedures for construction work involving safety measures was also uncovered just in November last year. Combined with this latest scandal, it must be said that corporate governance is severely lacking.

Since the 2011 nuclear accident at the Fukushima No. 1 nuclear power plant, every time a scandal surrounding nuclear power plants has come to light, the closed nature of the nuclear sectors within power companies has been pointed out as the underlying cause.

Chubu Electric intends to establish a third-party committee of external experts to investigate the case. It must identify the structural problems that allowed a spate of scandals to occur and implement fundamental organizational reform within its nuclear sector.

Nuclear power generation is becoming increasingly important as a means to achieve both decarbonization and a stable power supply. Last year, local consent was finally obtained for the restart of nuclear reactors at Tokyo Electric Power Company Holdings, Inc.’s Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture and Hokkaido Electric Power Co.’s Tomari nuclear power plant.

This latest misconduct could reverse such momentum. The impact is particularly significant for the Hamaoka plant because many people have long voiced concern about its safety as it is located within the presumed epicenter area of a possible Nankai Trough earthquake.

Strict safety screenings are imposed for restarting nuclear reactors in Japan. Electric companies must change their position of merely aiming to pass these screenings and instead focus their efforts on regaining the public trust they have lost.

(From The Yomiuri Shimbun, Jan. 7, 2026)