Nuclear Power Plant in Onagawa, operated by Tohoku Electric, to momentarily cease operations.
In the coastal town of Onagawa, Miyagi Prefecture, northeastern Japan, Tohoku Electric Power Co. has temporarily halted operations at its No. 2 reactor at the Onagawa nuclear power plant. The suspension, which began around August 2025, is due to the need to replace faulty equipment inside the reactor's containment vessel.
The devices in question are designed to measure the concentration of hydrogen gas produced if nuclear fuel and other materials melt during a nuclear accident. Two out of four of these devices were found to have malfunctions as early as June. In response, Tohoku Electric decided to replace all four units ahead of the originally planned schedule, a decision made possible by the procurement of necessary equipment.
The Onagawa plant's No. 2 reactor is a boiling water reactor, similar to the Fukushima No. 1 nuclear power plant, which experienced a meltdown in 2011. After resuming commercial operations in December 2024 following a temporary suspension for safety checks and equipment problems, the reactor went back online in October 2025 after an approximately 13-year hiatus.
The suspension is expected to last about 10 days, and the reactor is scheduled to resume operations in about 10 days. Tohoku Electric Power Co., the power utility responsible for the Onagawa nuclear power plant, is committed to ensuring the safety and reliability of its operations.
[1] Source: Tohoku Electric Power Co. press release, August 2025. [4] Source: Nuclear Regulation Authority of Japan, August 2025.
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