Tokyo, Jan 22 Japan's Tokyo Electric Power Company (TEPCO) said on Thursday it suspended operation at the just-restarted reactor of a nuclear power plant in Niigata Prefecture after an alarm went off.
The alarm was triggered at 00:28 a.m. local time after equipment to manoeuvre the control rods apparently had an issue, according to TEPCO.
TEPCO said it suspended work at reactor No. 6 to withdraw control rods, which are used to adjust the nuclear fission of a reactor, and it is looking into what happened at the Kashiwazaki-Kariwa plant.
The Nuclear Regulation Authority said the reactor is stable, adding that there are no safety problems, reports Xinhua news agency.
No abnormal levels of radioactivity were detected around the world's biggest nuclear power station by capacity, according to the Niigata prefectural government.
The No. 6 reactor at the seven-unit complex was reactivated shortly after 7 p.m. local time on Wednesday, marking the first operated by TEPCO to go back online since the 2011 Fukushima nuclear disaster.
The reboot came a day later than initially planned, after a control-rod alarm also sounded during testing.
Earlier on Wednesday, TEPCO restarted the reactor at the Kashiwazaki-Kariwa nuclear power plant, marking the first operated by TEPCO to go back online since the 2011 Fukushima nuclear disaster.
Reactor No. 6 at the seven-unit complex, about 220 kilometres northwest of Tokyo, began its nuclear reaction shortly after 7 p.m. local time. The utility said it received approval from the country's Nuclear Regulation Authority to conduct trial operations earlier in the day.
TEPCO initially planned to bring the reactor back online on Tuesday, but had to postpone due to an alarm malfunction during a test operation.
Despite a survey showing that residents were split over the resumption, Niigata Governor Hideyo Hanazumi gave the greenlight for plant restart last November, and the prefectural assembly followed up a month later.
The Kashiwazaki-Kariwa plant, the world's biggest nuclear power station capable of producing 8.2 gigawatts of electricity when at full capacity, was among 54 reactors shut following the March 2011 core meltdowns at TEPCO's tsunami-stricken Fukushima Daiichi plant.
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