Radioactive Steam Detected, Onagawa Nuclear Reactor to Halt for Inspection

• •Tohoku Electric Power Co. halted the No. 2 reactor at Onagawa nuclear plant for inspection.
• •Radioactive steam was detected, but no leakage into the environment occurred.
• •The incident is unrelated to a 6.4-magnitude earthquake that struck the region.

On May 16, 2026, Tohoku Electric Power Co. announced the halt of the No. 2 reactor at the Onagawa nuclear power station in Japan after radioactive steam was detected in its turbine building. The steam was found around 5:10 p.m. local time, but the company confirmed that no radioactive materials had leaked into the environment. The reactor had recently been brought back online after a regular inspection and was scheduled to resume commercial operations on June 9. The company also stated that there was no connection between this incident and a 6.4-magnitude earthquake that struck northeastern Japan later that night. This reactor had resumed power generation in November 2024, marking its first operation since the Fukushima disaster in 2011. The incident follows a similar steam leak at the Mihama nuclear power plant earlier in May, which was also contained without environmental impact.