The Japan Atomic Energy Research Institute manually shut down a nuclear reactor in Oarai, Ibaraki Prefecture, late Friday after potentially irradiated water leaked from a testing facility, officials said.
The leak, which occurred inside a water circulation control facility, began around 10 p.m. and lasted for about three hours, releasing 1.2 tons of water, the officials said.
The Japan Atomic Energy Research Institute said in a report the water may contain a small amount of radioactive material, but it did not escape beyond the facility and no institute employee was exposed to radiation.