The Nuclear Regulation Authority on Jan. 7 suspended its safety review of the Hamaoka nuclear power plant after concluding that operator Chubu Electric Power Co. deliberately understated the dangers of an earthquake there.

“This is an outrage against safety regulations. The review itself needs to be redone,” NRA Chairman Shinsuke Yamanaka said at a news conference.

Chubu Electric on Jan. 5 disclosed that it had used inappropriate data on estimating the “standard ground motion” during a safety review of the No. 3 and 4 reactors at the Hamaoka nuclear plant in Shizuoka Prefecture.

Standard ground motion represents the maximum potential shaking from an earthquake. A nuclear plant must be designed to withstand such shaking, making the assessments critical for safety.

At its meeting on Jan. 7, the NRA judged that Chubu Electric engaged in fraudulent activity, stating that the quake data was arbitrarily manipulated using a method different from what was explained in the review.

“This is a case of fabricating safety-related review data. It is extremely serious and grave,” Yamanaka said.

He ordered the nuclear industry watchdog to respond independently without waiting for the results of Chubu Electric’s internal investigation into the matter.

INSPECTIONS LOOM

At its next meeting on Jan. 14, the NRA will consider demanding a legally mandated report and conducting a nuclear regulatory inspection that includes on-site access to Chubu Electric’s headquarters and the Hamaoka plant.

Such inspections are compulsory and carry penalties for refusal to cooperate.

Koshun Yamaoka, an NRA commissioner in charge of reviewing earthquake and tsunami data, criticized Chubu Electric for reporting smaller seismic waves.

“They manipulated diagrams to make their data appear plausible,” Yamaoka said. “Compared with research misconduct, this is equivalent to fabrication or falsification. This is a serious matter that fundamentally overturns the premise of the review.”

NRA Commissioner Reiko Kanda also blasted Chubu Electric for an act that “has wasted national funds.”

“We have invested human resources and conducted our review in good faith,” Kanda said.

NRA Commissioner Tomoyuki Sugiyama said the safety review should remain halted until the reliability of Chubu Electric’s data can be assured.

“I was utterly disappointed. Although we are temporarily suspending the review, there is no way we can resume it,” he said.

HIGH-STAKES LOCATION

All reactors at the Hamaoka nuclear power plant in Omaezaki, Shizuoka Prefecture, were shut down at the request of the central government following the 2011 Great East Japan Earthquake and tsunami.

The No. 1 and 2 reactors are currently being decommissioned, while Chubu Electric aims to restart reactors No. 3 through 5.

The company applied for the review of the No. 3 and 4 reactors in 2014 and 2015.

The nuclear plant is located within the assumed epicentral region of a Nankai Trough earthquake, meaning it requires stringent seismic resistance.

Standard ground motion assessments are based on surveys of active faults, ground conditions and other geological features.

A higher assessment would increase the cost of safety measures needed for greater seismic resistance at a nuclear plant.

During the 2011 disaster, shaking from the earthquake exceeded the standard at the site of Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power plant, which experienced a triple meltdown.

The NRA in 2023 had viewed Chubu Electric’s standard ground motion at the Hamaoka plant as “generally appropriate.”

But in February last year, the NRA received a tip from an external source that Chubu Electric was engaged in fraudulent activity, prompting it to demand the company submit materials and provide an explanation.

The utility conducted an internal investigation and told the NRA on Dec. 18 that it had “confirmed fraudulent activity.”

The falsified data became public on Jan. 5.

OUTRAGE IN SHIZUOKA

Local leaders and officials from Omaezaki, the host municipality of the plant, also had harsh words for Chubu Electric.

“The premise of the review under the new regulatory standards has collapsed. It is a deeply regrettable event that causes a loss of trust,” Shizuoka Governor Yasutomo Suzuki told reporters on Jan. 7.

Citing a series of scandals at the utility, he added, “I will be closely watching its future initiatives, including corporate culture reform."

He also said he will demand an explanation from Chubu Electric after receiving a report from a third-party committee investigating the false data and will petition the central government for guidance.

Omaezaki Mayor Masaru Shimomura said it will be difficult to restart the plant without the trust of the region.

“If the reliability of the submitted data itself is shaken, then everything is shaken,” he said at a news conference on Jan. 6.

The mayor said he has refused to accept the annual New Year’s greeting from Chubu Electric.

The reaction to the data falsification was equally strong from municipalities within the plant’s 31-kilometer emergency evacuation zone.

At a news conference on Jan. 6, Shohei Kitamura, the mayor of Fujieda, said if the act was intentional, it is “a major betrayal of our citizens.”

Shimada Mayor Kinuyo Someya said on the same day that the false data “shakes our trust in Chubu Electric from its very foundations.”

“The national energy policy is to actively promote the restart of nuclear power plants, but this will cause delays to that policy,” Someya said.