Japan suspends world’s largest nuclear plant hours after restart

Japan has suspended operations at the world’s largest nuclear power plant, hours after its restart, its operator has said.

An alarm sounded “during reactor-start-up procedures” at Kashiwazaki-Kariwa north-west of Tokyo but the reactor remained “stable”, Tokyo Electric Power Company (Tepco) spokesperson Takashi Kobayashi said.

Reactor number six restarted on Wednesday a day later than planned due to an alarm malfunction – the first at the plant to be turned on since the 2011 Fukushima disaster.

Japan shut down all of its 54 reactors after a 9.0 magnitude earthquake triggered a meltdown at its Fukushima plant 15 years ago, causing one of the worst nuclear disasters in history.

At the time, radiation leakage from the plant forced more than 150,000 people to evacuate their homes. Many have not returned despite assurances it is now safe.

Following the suspension of reactor number six on Thursday, Kobayashi said it was “stable and there is no radioactive impact outside”.

The reactor was initially set to start on Tuesday, but was pushed back due to a technical issue. It is due to begin operating commercially next month.

Kobayashi said Tepco was “currently investigating the cause” of the incident and did not say when operations would resume.

The seventh reactor at Kashiwazaki-Kariwa is not expected to be turned back on until 2030, while the other five could be decommissioned.

This would leave the plant with far less capacity than it once had when all seven reactors were operational.

Reactor number six was given the green light to restart despite safety concerns from local residents.

A small crowd of people gathered outside Tepco’s headquarters to protest last week, while hundreds gathered outside the Niigata prefectural assembly in December.

Japan was an early adopter of nuclear power – before 2011, nuclear accounted for nearly 30% of its electricity and the country planned to get that up to 50% by 2030.

After it was forced to shut them all down in the wake of the Fukushima disaster, it has spent the past decade attempting to revive the plants as part of its goal to reach net zero emissions by 2050.

Since 2015, Japan has restarted 15 out of its 33 operable reactors.

An earlier version of this story said the Kashiwazaki-Kariwa nuclear plant was in Tokyo and has been corrected to say it is north-west of Tokyo.