A Japanese nuclear power operator has acknowledged it may have submitted data underestimating earthquake risks to regulators, raising concerns as Japan moves to revive nuclear energy nearly 15 years after the Fukushima disaster.
Chubu Electric Power, which operates the Hamaoka nuclear plant in central Japan, said the facility is currently undergoing regulatory safety inspections as part of efforts to restart two reactors. The plant is located in a region considered vulnerable to a potential “megaquake.”
Speaking at an emergency press conference on Monday, the company’s president admitted that the estimated maximum seismic ground motion the plant could face during an earthquake may have been underestimated. He warned that the issue could seriously impact the safety review process, erode public trust, and undermine the foundations of the company’s nuclear operations.
Japan shut down most of its nuclear facilities after the 2011 earthquake and tsunami triggered meltdowns at the Fukushima Daiichi plant. However, the country is now seeking to bring nuclear power back online to cut reliance on fossil fuels, achieve carbon neutrality by 2050, and meet rising energy demand driven by technologies such as artificial intelligence.
Meanwhile, the world’s largest nuclear plant, Kashiwazaki-Kariwa, is expected to resume operations later this month, subject to final approval from the Nuclear Regulation Authority (NRA).
Accurate estimates of maximum seismic ground motion are critical for designing earthquake-resistant nuclear facilities. In September 2023, the NRA approved Chubu Electric’s estimate of 1,200 gal, a unit measuring seismic acceleration. However, in February last year, the regulator received a whistleblower tip suggesting the company may have relied on data different from what it officially submitted.
An NRA investigation has been underway since then. The authority suspended the Hamaoka plant’s safety review in late December and announced that the issue will be discussed in public meetings, starting Wednesday.
The Hamaoka plant is located in Omaezaki, Shizuoka Prefecture, near a major fault line along the Nankai Trough, where a massive Pacific earthquake is expected in the coming years or decades. In 2024, the Japan Meteorological Agency issued — and later lifted — its first special advisory warning of a possible megaquake in the region.
The Japanese government estimates that a major quake and tsunami in the area could result in up to 298,000 deaths and cause damage worth as much as $2 trillion. Chubu Electric said it has formed an independent panel of lawyers to investigate the matter further.
