Japan shuts reactor at world’s biggest nuclear plant a day after restart

Restart of No 6 reactor at Kashiwazaki-Kariwa plant suspended after malfunction related to control rods.Published On 22 Jan 2026The restart of a reactor at the world’s largest nuclear power plant has been suspended in Japan, a day after the process began, its operator, which also manages the wrecked Fukushima plant, said. But the reactor remains “stable”.The No 6 reactor at the Kashiwazaki-Kariwa plant in north-central Japan – closed since the 2011 Fukushima disaster – reactivated on Wednesday as plant workers started removing neutron-absorbing control rods from the core to start stable nuclear fission.Recommended Stories list of 3 itemslist 1 of 3Japan to restart world’s biggest nuclear plant after 15-year shutdownlist 2 of 3Japan gov’t greenlights record $58bn defence budget amid regional tensionlist 3 of 3Japan, Philippines sign new defence pacts amid surging China tensionsend of listBut the process had to be suspended hours later due to a malfunction related to control rods, which are essential to safely starting up and shutting down reactors, the Tokyo Electric Power Company Holdings (TEPCO) said. The duration of the shutdown was still unknown.TEPCO said there was no safety issue from the glitch and it was checking the situation while suspending the restart operation. The utility later said it was putting the reactor back into shutdown for a fuller examination.“We were investigating the malfunctioning electrical equipment,” spokesperson Takashi Kobayashi told the AFP news agency.The reactor “is stable and there is no radioactive impact outside”, he said.Control rods are a device used to control the nuclear chain reaction in the reactor core, which can be accelerated by slightly withdrawing them, or slowed down or stopped completely by inserting them deeper.The restart, initially scheduled for Tuesday, had been pushed back after another technical issue related to the rods’ removal was detected last weekend – a problem that was resolved on Sunday, according to TEPCO.Kashiwazaki-Kariwa is the world’s biggest nuclear power plant by potential capacity, although just one reactor of seven was restarted.