Kansai Electric Power announced the shutdown of Reactor No. 3 at the Mihama nuclear power plant in Fukui Prefecture, central Japan, after detecting a steam leak near a high-pressure turbine.

The company stated that the leak did not involve radioactive materials and caused no environmental impact, noting that the reactor was manually shut down as a precautionary measure minutes after the incident was discovered.

The reactor is among Japan’s oldest nuclear facilities, having begun operations in 1976, and continued functioning beyond 40 years under updated regulatory rules introduced after the 2011 Fukushima disaster.