The operator of the Onagawa nuclear power station in Miyagi Prefecture, northeastern Japan, announced the temporary shutdown of its No. 2 reactor following the detection of radioactive steam within its turbine building. Tohoku Electric Power Co. confirmed the presence of a small amount of radioactive steam at the reactor unit’s turbine building, emphasizing that no radioactive materials had been released into the environment. The halt was initiated for inspection purposes and not due to any connection with a recent 6.4-magnitude earthquake in the region.
The No. 2 reactor at the Onagawa plant had been offline for a routine inspection and had only been reactivated on Monday, with plans for commercial operations to resume on June 9. In a separate incident on May 8, a reactor at a nuclear power plant in Fukui Prefecture, central Japan, was shut down due to a steam leak near the high-pressure turbine. The No. 3 reactor of the Mihama nuclear power plant experienced the steam leak, prompting Kansai Electric Power Co. to manually shut down the reactor, assuring that the steam did not contain any radioactive material and posed no threat to the external environment.
The No. 3 reactor at the Mihama plant, which commenced operations in 1976, had been temporarily decommissioned after the 2011 Fukushima nuclear disaster but resumed operation in 2021. Similarly, the Onagawa nuclear plant’s reactor had resumed power generation in November 2024 for the first time since the Fukushima disaster in 2011. Tohoku Electric Power Company confirmed the restart of power generation at the Onagawa No. 2 reactor, outlining plans for temporary halts to conduct equipment checks after an adjustment operation to ensure normal functioning.
The 825,000-kilowatt reactor at the Onagawa plant, if operated at around 70% capacity for a year, is projected to generate electricity equivalent to the consumption of 1.62 million households. Notably, the three reactors at the Onagawa facility share the same boiling water design as those at Tokyo Electric Power Company’s Fukushima Daiichi nuclear plant, which was the site of Japan’s worst nuclear disaster triggered by the 2011 earthquake and tsunami.
