By The restart of the world’s largest nuclear power plant, Kashiwazaki-Kariwa, was suspended in Japan on Thursday after an alarm was triggered during reactor startup procedures, the plant’s operator, Tokyo Electric Power Company (TEPCO), has confirmed.
The nuclear facility, located in Niigata Province, had been shut down since the 2011 Fukushima nuclear disaster. Operations to relaunch the plant resumed on Wednesday after it received final regulatory approval from Japan’s Nuclear Regulation Authority.
Technical Alarm Forces Suspension
According to TEPCO, an alarm from the monitoring system sounded during reactor startup, prompting an immediate suspension of operations.
“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,” Kashiwazaki-Kariwa site superintendent Takeyuki Inagaki told reporters.
He added that engineers are currently focused on identifying the cause of the issue.
TEPCO spokesperson Takashi Kobayashi explained that the alarm led to an investigation into malfunctioning electrical equipment. As a precautionary measure, control rods were reinserted into the reactor in a planned and safe manner.
“The reactor is stable, and there is no radioactive impact outside the facility,” Kobayashi said.
Control Rods Reinserted as Safety Measure
Control rods regulate nuclear reactions within a reactor core. They are withdrawn to increase power output and inserted to slow or completely stop the reaction. TEPCO emphasized that the reinsertion was conducted safely and according to established protocols.
The restart had already been delayed earlier this week due to another technical issue related to control rod removal, which was resolved on Sunday.
About Kashiwazaki-Kariwa Nuclear Plant
Kashiwazaki-Kariwa is the largest nuclear power plant in the world by installed capacity, with seven reactors, although only one reactor was slated for restart.
The facility was taken offline following the 2011 earthquake and tsunami that triggered meltdowns at the Fukushima Daiichi nuclear plant, also operated by TEPCO and currently undergoing decommissioning.
Japan Pushes Nuclear Energy Revival
Despite lingering safety concerns, Japan is seeking to revive nuclear power to reduce dependence on fossil fuels, meet rising electricity demand driven by artificial intelligence and digital infrastructure, and achieve carbon neutrality by 2050.
The Kashiwazaki-Kariwa restart would mark the first TEPCO-operated reactor to return to service since 2011.
Public Opposition Remains Strong
Public opinion in Niigata remains divided. A September survey showed that about 60 percent of residents oppose the restart, while 37 percent support 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.
Earlier this month, seven anti-nuclear groups submitted a petition with nearly 40,000 signatures to TEPCO and Japan’s Nuclear Regulation Authority. The petition cited concerns that the plant sits on an active seismic fault zone and referenced damage caused by a powerful earthquake in 2007.
