A reactor at the Kansai nuclear power plant in Japan's Fukui prefecture has been halted due to a problem with its cooling system, Kyodo quoted the plant's operator as saying on Saturday.
A probe will be launched to establish the cause of the glitch, government officials said.
The government's Nuclear and Industrial Safety Agency said the problem with the No. 1 reactor at the plant will not have an adverse effect on the environment.
According to the agency, the pressure inside the accumulator in the reactor's emergency core cooling system fell on Friday, setting off an alarm.
The pressure has stabilized since, but the utility began reducing the power of the reactor at 1 p.m. Saturday and halted it after 8:50 p.m. to determine what caused the problem, Kyodo reported.
