A reactor at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture shut down automatically Sunday afternoon, but no radioactivity leaked from the plant and no other environmental damage was observed, the Nuclear and Industrial Safety Agency said.
The plant's No. 5 reactor came to an emergency halt at around 2:37 p.m. after a condenser malfunctioned, the agency said.
The shutdown took place as workers were preparing for a regular checkup of the reactor beginning Monday, according to Tokyo Electric Power Co., the plant's operator.
The reactor was put into operation in April 1990.
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