In a scene that felt both inevitable and devastating, Chubu Electric Power Co. announced on Sept. 14 that its president and chairman would resign and that it would withdraw its application to restart a nuclear plant, after an internal investigation exposed years of systematic seismic data manipulation. At a news conference in Nagoya, President Kingo Hayashi and Chairman Satoru Katsuno bowed in apology, offering words that seemed to acknowledge the depth of the betrayal. “I would like to once again offer my deepest apologies for the repeated incidents of misconduct, which have caused great concern and inconvenience to local residents and many other stakeholders, and have seriously undermined the trust of society as a whole,” Hayashi said. Katsuno echoed the sentiment, saying, “I deeply apologize for having caused a result that has severely damaged trust in our company.” The resignations, effective at the end of September, were the predictable conclusion to a scandal that had been brewing for months. The investigative report, released the same day, found manipulation in at least 208 of 225 earthquake assessments at the Hamaoka nuclear power plant in Shizuoka Prefecture. The misconduct, the report concluded, dated back to at least 2012 and was not a one-off lapse in judgment but a deliberate, sustained effort to prevent delays in restarting two reactors at the plant. For a nation still haunted by the Fukushima disaster, the news landed like a gut punch, a painful reminder that the lessons of the past do not always take root.
To understand what happened, one must understand the stakes at Hamaoka. The plant sits in a region that seismologists have long warned could be struck by a massive Tokai earthquake, making its safety assessments uniquely critical. In the world of nuclear regulation, numbers carry enormous weight. The company’s reactor restart application assumed that calculated seismic ground motion would not significantly exceed 1,200 gal, a unit of acceleration used to measure the intensity of earthquake shaking. If the numbers had come in higher, regulators would have required additional safety assessments and construction work, which would have delayed the restart plans. That, according to the investigative committee, is precisely why employees manipulated the data. They wanted to keep the numbers below the threshold, to avoid the costly and time-consuming consequences of an honest assessment. The report, compiled by three external lawyers who began their investigation in January and delivered their findings to the company on Sept. 11, painted a picture of a workplace where the goal of restarting reactors had become so dominant that it corrupted the very processes meant to ensure safety. The manipulation was not limited to a few rogue employees; it was embedded in the culture of the nuclear civil engineering and construction department, which instructed contractors to alter data while coordinating closely with the departments responsible for seismic design. The sheer scale of the misconduct—208 of 225 assessments—suggests that what began as an attempt to cut corners became a normalized way of doing business.
Why would experienced engineers and managers risk their careers, their reputations, and the safety of their community? The investigative report points to management pressure, and the language it uses is chilling. From 2017 onward, Katsuno, who was president at the time and later became chairman, made comments at meetings about the slow pace of the reactor restart review process. He was quoted as saying it was “progressing as slowly as an inchworm” and that “it is simply because our efforts have been insufficient.” The report stopped short of calling those remarks inappropriate, but it concluded that management’s criticism of delays, made without adequately understanding the realities of the Nuclear Regulation Authority’s examination procedures, “acted as pressure and became one of the factors that led to the misconduct.” At the news conference, Katsuno defended his words, saying, “I did not intend to rush them any more than necessary. My intention was to advance goal management and other efforts to ensure greater certainty.” But he also accepted responsibility, acknowledging, “As executive vice president and president, I have been at the center of the company’s management. I recognize that I bear an extremely heavy responsibility for failing to prevent this incident.” The report also identified a deeper cultural problem: employees had developed what the committee called a “unique theory of justification,” under which rule violations were tolerated if they believed plant safety was not at risk. This is perhaps the most troubling finding of all. It suggests that the people manipulating the data genuinely convinced themselves that they were doing nothing wrong, that the rules were obstacles rather than protections, and that their mission—restarting the reactors—was more important than the process designed to verify their safety.
The technical details of the manipulation reveal a sophisticated and deliberate deception. According to the report, the company had told regulators that it generated 20 sets of seismic waves using random numbers and then selected the one closest to the average as the “representative wave.” This was a lie. In reality, employees chose a representative wave from a larger pool of seismic waves and then selected the remaining 19 waves specifically to make that chosen wave appear closest to the average. The effect was to create the illusion of a rigorous, randomized process when in fact the results had been carefully curated to produce the desired outcome. The misconduct occurred during safety reviews related to the applications to restart the No. 3 and No. 4 reactors at Hamaoka, meaning the deception was directly connected to the company’s most important business priority. The report found that the nuclear civil engineering and construction department, which was responsible for establishing the plant’s design basis seismic ground motion, instructed contractors to manipulate the data while closely coordinating with the departments responsible for seismic design. This was not a case of one person fudging a calculation in isolation; it was a coordinated effort involving multiple teams and outside contractors, all working toward the same goal. The sophistication of the scheme also made it harder to detect. By creating a false narrative of randomness, the company had a ready-made explanation for why the data looked the way it did. It was only after a tip-off prompted the Nuclear Regulation Authority to begin looking into the allegations in May 2025 that the cracks in that narrative began to show.
Equally disturbing is what happened to the people who tried to speak up. The investigative report found that multiple employees raised concerns internally about the manipulation, but their objections were suppressed. In a workplace culture that tolerated rule-breaking as long as employees believed safety was not compromised, dissent was seen as an obstacle to the mission rather than a necessary check on power. The report concluded that although oversight and monitoring mechanisms existed within the company, they “did not function effectively.” This is a damning statement, because it means the company had the tools to catch the misconduct but lacked the will or the culture to use them. Investigators also found efforts to conceal the misconduct after the NRA began investigating, suggesting that the instinct to protect the company and the restart project remained stronger than the instinct to come clean. The report also noted that requirements imposed during NRA safety reviews could, by their nature, become excessively conservative from a safety standpoint, and suggested that a mechanism capable of providing answers from a neutral and fair standpoint may eventually need to be established. This observation is not an excuse for the misconduct, but it does highlight a systemic issue in nuclear regulation: when regulators demand ever-higher levels of safety, companies may feel pressure to manipulate the system to meet those demands, rather than to engage honestly with them. The committee also noted that a similar mindset appeared to underlie other scandals involving the utility, suggesting that this was not an isolated failure but a pattern of behavior rooted in the company’s culture.
What comes next for Chubu Electric and for the Hamaoka nuclear power plant is far from clear. The utility has announced that it will withdraw its application to the Nuclear Regulation Authority for a restart review, effectively pausing its plans to bring the two reactors back online. But in the same breath, the company said that “the importance of the Hamaoka nuclear power plant remains unchanged,” expressing its intention to pursue a restart once it has restored public trust. Hayashi, who succeeded Katsuno as president in 2020, has acknowledged that he was responsible for rebuilding the company’s nuclear power operations. That task now seems almost insurmountable. How does a company restore trust after admitting that it manipulated seismic data for years, suppressed internal dissent, and tried to conceal its misconduct after being caught? An apology, no matter how sincere, cannot undo the damage. For local residents, many of whom have lived their entire lives in the shadow of the plant, the news is a profound betrayal. They were told the plant was safe. They were told the data was sound. They now know that the people responsible for their safety were willing to bend the truth to meet a business goal. The road back will be long, and it will require more than resignations and withdrawn applications. It will require a fundamental change in culture, from one that prioritizes restarts to one that prioritizes transparency and safety above all else. It will require independent oversight that cannot be co-opted or ignored. And it will require a recognition, from the top of the company to the bottom, that nuclear safety is not just a technical challenge but a human one. In a country that has lived with the consequences of nuclear disaster, the Hamaoka scandal is a painful reminder that safety cannot be left to the discretion of those who have something to gain from cutting corners. Trust, once broken, is not easily restored. But it can be rebuilt, one honest assessment at a time.