CNIC Statement: Data Fabrication Found in Formulating the Basic Earthquake Ground Motion for Hamaoka Nuclear Power Station – We demand a thorough investigation and a comprehensive review of the past screening process.
January 8, 2026
On January 5, Chubu Electric Power announced that it had “suspicions that the selection of representative waves in the ground motion evaluation for the Hamaoka Nuclear Power Station had been conducted using different methods or deliberately misleading methods” compared to those given in explanations at the Nuclear Regulation Authority’s (NRA’s) review meeting. [i] On the same day, the Minister of Economy, Trade and Industry requested a report under Article 106, Paragraph 3 of the Electricity Business Act. [ii]
On January 7, an overview of Chubu Electric Power’s misconduct case was reported at the 50th NRA meeting [iii]. According to the report, information was provided under the Nuclear Facility Safety Information Reporting System as of February 2025, based on which the NRA had held multiple meetings with Chubu Electric since May. Then, during a meeting on December 18, Chubu Electric explained that its internal investigation had also confirmed the misconduct. This case, however, involves neither “suspicion” nor “misconduct;” it is fabrication and falsification. The Nuclear Regulation Authority should immediately reject the Hamaoka NPS’s review application, following the precedent set by the Tsuruga Nuclear Power Station.
At the review meeting, Chubu Electric explained that “in formulating the basic earthquake ground motion, regarding the ground motion evaluation using the ‘Stochastic Green’s Function Method,’ a procedure involving the calculation of ‘20 sets of ground motions’ with different calculation conditions and selecting the wave ‘closest to the average wave’ would be used.” However, in practice, this was not the case. Prior to 2018, “multiple sets of ‘20 sets of ground motions and their representative waves’ were created, and from these ‘one set of representative waves’ was selected.” Furthermore, after 2018, “‘representative waves that were not the closest to the average’ were intentionally selected, and then the remaining 19 sets were selected so that the representative wave would be closest to the 20 sets, to create a set of ‘20 sets of ground motions and their representative waves.’” According to the NRA explanation, 2018 was the peak period for reviews of inland crustal earthquake, and this coincided with the time when active faults near the site became the subject of ground motion evaluation. Before 2018, the problem was that an evaluation method that differed from the provided explanation was used, as well as arbitrariness entering into the process at the selection stage. After 2018, a method that results in undervaluation was deliberately chosen, and this is an extremely serious problem.
Chubu Electric stated it will establish a third-party committee to investigate the case. However, one of the committee members is attorney Morikawa Hisanori. After joining TMI Associates, Mr. Morikawa was seconded to the NRA where he acted as a designated representative for the government in lawsuits to halt nuclear power plant operations and lawsuits for damage arising from the Fukushima Daiichi nuclear power plant accident. Since returning to his firm, he is serving as a representative of Tokyo Electric power Company. His neutrality is therefore questionable.
Since it involves the fabrication and falsification of data for determining the basic earthquake ground motion, this case is absolutely unacceptable. At the same time, the fact that this has been repeated in the past is also a problem. The nuclear power divisions of electric companies are highly specialized and insular organizations. Thinking back, the closed nature of the nuclear power division was also pointed out in the issue of long-standing and substantial unsettled payments at Chubu Electric Power [iv]. Following this, cover-ups of problems at all nuclear power stations operated by Tokyo Electric Power Company, which came to light in 2002, were also exposed by an internal whistleblower. It was later discovered that Chubu Electric Power, Tohoku Electric Power and Japan Atomic Power Company had also concealed problems at their nuclear power stations.
The NRA will decide on the review of the Hamaoka Nuclear Power Station at its regular meeting on January 14, stating that it will be a very weighty decision. Meanwhile, there are no plans to implement a horizontal rollout to other companies, since the primary responsibility for ensuring safety lies with the nuclear power plant operators; the relationship between the operators and the regulator is one of “trust, but verify,” and no deterioration in safety culture has been observed in inspections of other companies.
Even so, the NRA failed to detect the deterioration of safety culture at Chubu Electric until 2025, when an internal whistleblower came forward. Just because deterioration in the safety culture of other operators is not yet detectible, does not mean it does not exist. Furthermore, and more critically, it has become clear that the NRA currently lacks the ability to detect falsifications even if application materials are manipulated. The NRA should revise the current review system, requiring operators to submit primary data rather than processed secondary materials, and make the data publicly available. It is also necessary to ensure the traceability of the calculation process. Although all documents submitted thus far have been in the name of the business operator, there must be personnel who actually performed the calculations or contracted service providers who are responsible for the work. It is necessary to clarify the scope of responsibility by clearly specifying the names of those people.
This case highlighted not only the issues with Chubu Electric but also fundamental problems with the current regulatory system itself. Both a fundamental review of the regulatory system and a horizontal rollout to other companies are essential.
[All links in Japanese]
[i] www.chuden.co.jp/publicity/press/1217264_3273.html
[ii] www.meti.go.jp/press/2025/01/20260105002/20260105002.html
[iii] www.da.nra.go.jp/detail/NRA100015154
[iv] www.chuden.co.jp/publicity/press/__icsFiles/afieldfile/2025/12/24/20251224.pdf
