Photo/Illutration Chubu Electric Power Co. President Kingo Hayashi, right, apologizes during a news conference in Nagoya on Jan. 5. (Kohei Kondo)

NAGOYA--Chubu Electric Power Co. on Jan. 5 acknowledged irregularities in the seismic safety assessment for its Hamaoka nuclear power plant, an error that will likely delay the restart of two reactors there.

The company said it used a method to evaluate “standard ground motion”—the maximum expected earthquake shaking—that was different from what it had explained to the Nuclear Regulation Authority during its safety review of the plant.

Such assessments are fundamental to a nuclear plant’s seismic resistance. The discrepancy will make an early restart of the No. 3 and No. 4 reactors at the plant on the coast of Omaezaki, Shizuoka Prefecture, difficult.

The company said the background behind the irregularities remains unclear. It will establish a third-party committee of external lawyers to investigate the details.

Chubu Electric President Kingo Hayashi apologized for the problems at a news conference in Nagoya.

“We view this matter extremely seriously as it could significantly impact the review process, undermine trust in our nuclear power business, and potentially shake the very foundation of our operations,” he said. “We intend to tackle this issue with resolve and might consider a fundamental restructuring of the nuclear power division.”

Hayashi also serves as chairman of the Federation of Electric Power Companies of Japan, a key proponent of nuclear power.

He said he acknowledged his “significant responsibility” in both roles.

Asked if he would resign, Hayashi said he will “consider the matter comprehensively” based on the findings of the independent committee investigation.

The company disclosed last November that it had conducted safety improvement work without formal contracts and had failed to settle accounts for an extended period.

In response to the latest problem, Shizuoka Governor Yasutomo Suzuki said in a statement, “This is a serious matter that undermines the trust of our citizens, and it is deeply regrettable.”

The prefectural government not only plans to demand the company provide a thorough investigation and explanation, but it will also ask the central government to conduct a strict review and provide guidance.

The Hamaoka plant, located in an assumed focal region of a Nankai Trough earthquake, shut down all five of its reactors at the government’s request following the 2011 Great East Japan Earthquake and tsunami.

The company has been seeking to restart the No. 3, 4 and 5 reactors at the plant, and the NRA is currently reviewing the first two units.

Chubu Electric’s standard ground motion assessment received general approval in September 2023, as did its assessment for the maximum expected tsunami in 2024.

The broader review of the Hamaoka nuclear plant was reportedly halted on Dec. 22 last year.

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