MIHAMA, Japan, Aug. 9 (UPI) -- A steam leak at a Japanese nuclear reactor killed four workers and injured at least 11 others Monday, the Kyodo news agency reported.
The sudden blast of steam occurred at a building housing the turbines for the No. 3 reactor of the Mihama Nuclear Power Plant, but there was no external leak of vapor or radiation.
The 826,000-kilowatt pressurized-water reactor automatically shut down, the government Nuclear and Industry Safety Agency said in a statement.
The leak is believed associated with trouble in the secondary circulation system, firefighters said.
Five of the injured were in critical condition, suffering from heart and lung failure, Kyodo said.
The reactor has been in service since December 1976. In February 1991, a tube inside a steam generator at the No. 2 reactor in the same plant broke, resulting in a leak of 55 tons of radioactive water from the main cooling system into the secondary system that powers the reactor's turbine.
The Vienna-based International Atomic Energy Agency, the United Nation's nuclear watchdog, said it was monitoring the situation.