SAFETY & SECURITY | RESTARTING HAMAOKA
Hamaoka safety review suspended
After Chubu Electric Power Company deliberately understated the
dangers of seismic activity at the Hamaoka NPP site, the NRA suspended its safety review – a critical step in the restart programme for the plant. The move puts the restart plan in jeopardy.
By Judith Perera
Above: Japan suspended operations of its entire nuclear fleet in the wake of the Fukushima-Daiichi disaster and the NRA requires stringent safety testing for restarting nuclear units Source: OECD
JAPAN’S NUCLEAR REGULATION AUTHORITY (NRA) has suspended its safety review of the Hamaoka NPP in Shizuoka Prefecture after concluding that plant owner and operator, Chubu Electric Power Company, had deliberately understated the dangers of an earthquake at the site. This came two days after Chubu Electric disclosed that it had used inappropriate data to estimate the earthquake standard ground motion during a safety review of units 3&4. Standard ground motion represents the maximum
potential shaking from an earthquake, which a NPP must be designed to withstand. Hamaoka NPP comprises five units – four boiling water
reactors (BWRs) and one advanced boiling water reactor (ABWR). Units 1 and 2, the two oldest (540 MWe and 840 MWe) were permanently shut down in 2009 and are currently being decommissioned. Hamaoka units 3-5 were shut down after the Fukushima accident in 2011 and underwent significant safety upgrades. In 2014, Chubu Electric applied to the NRA to restart them by initiating a safety review. Chubu Electric had aimed to finalise both the plant facility screenings – covering reactor buildings and equipment – and the investigations of on-site geological faults by the spring of 2026.
34 | January 2026 |
www.neimagazine.com
In 2023 the NRA had viewed Chubu Electric’s standard
ground motion at the Hamaoka plant as “generally appropriate”. However, in February 2025, NRA received information from an external source that Chubu Electric was engaged in fraudulent activity, prompting it to demand that the company submit materials and provide an explanation. Chubu conducted an internal investigation and told the NRA in December that it had “confirmed fraudulent activity”. NRA subsequently stated that the quake data was
arbitrarily manipulated using a method different from what was indicated in the review. According to Chubu Electric, at a regulatory review meeting in 2019, the company had told the NRA that it would calculate a set of 20 seismic ground motion estimates based on different conditions to serve as data for calculating a representative or average figure for the safety standards at the Hamaoka NPP. However, prior to 2018, instead of preparing a single set
consisting of 20 simulations of seismic motion, the company had been creating multiple sets and selected just one of them to submit to the NRA. At some point after 2018, the company had selected one simulation that was not closest to
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