Japan suspends restart of world’s biggest nuclear plant

The restart of the world’s largest nuclear power plant has been suspended in Japan, just a day after operations resumed, with the operator saying it remains unclear when the issue will be resolved.

The Kashiwazaki-Kariwa Nuclear Power Plant had been shut since the 2011 Fukushima disaster, but began restart procedures on Wednesday after receiving final approval from regulators. On Thursday, however, its operator, Tokyo Electric Power Company, said an alarm was triggered during startup, forcing a halt to operations.

“An alarm from the monitoring system… sounded during the reactor startup procedures,” the company said. Site superintendent Takeyuki Inagaki told a news conference: “We don’t expect this to be solved within a day or two. There is no telling at the moment how long it will take. We will for now fully focus on trying to identify the cause of what happened.”

TEPCO spokesperson Takashi Kobayashi said the alarm led engineers to investigate malfunctioning electrical equipment. “Once it became clear that it would take time, we decided to reinsert the control rods in a planned manner,” he said, adding that the reactor “is stable and there is no radioactive impact outside.”

Control rods regulate the nuclear chain reaction in a reactor core, accelerating it when withdrawn slightly and slowing or stopping it when fully inserted. The restart had already been delayed from Tuesday after a separate technical issue related to rod removal was detected last weekend, a problem TEPCO said was resolved on Sunday, January 18.

Kashiwazaki-Kariwa, located in Niigata prefecture, is the largest nuclear power station in the world by potential capacity, although only one of its seven reactors was involved in the restart. The facility was taken offline when Japan suspended nuclear power nationwide after the earthquake and tsunami in 2011 triggered meltdowns at the Fukushima Daiichi Nuclear Power Plant.

Japan, which lacks natural energy resources, has moved to revive nuclear power to cut fossil fuel dependence, meet rising electricity demand linked to artificial intelligence, and achieve carbon neutrality by 2050. Kashiwazaki-Kariwa is the first TEPCO-run unit to attempt a restart since 2011, as the company continues decommissioning work at Fukushima Daiichi.

Public opinion in Niigata remains divided. A September survey found around 60 percent of residents opposed the restart, while 37 percent supported it. “It’s Tokyo’s electricity that is produced in Kashiwazaki, so why should the people here be put at risk? That makes no sense,” said 73-year-old resident Yumiko Abe during a protest outside the plant this week.

Earlier this month, seven groups opposing the restart submitted a petition signed by nearly 40,000 people to TEPCO and Japan’s Nuclear Regulation Authority, arguing the plant sits on an active seismic fault zone and citing damage from a strong earthquake that struck the area in 2007.