Japan on Thursday suspended the restart of the world’s largest nuclear power plant, with the operator unable to provide a timeline for resolving the issue.
The Kashiwazaki-Kariwa plant in Niigata Prefecture, which has been offline since the 2011 Fukushima disaster, began procedures to resume operations on Wednesday after receiving final approval from the country’s nuclear regulator.
However, Tokyo Electric Power Company (TEPCO), the plant’s operator, reported that “an alarm from the monitoring system sounded during reactor startup procedures,” prompting an immediate halt.
“We don’t expect this to be resolved within a day or two. At this stage, it is unclear how long it will take,” said site superintendent Takeyuki Inagaki at a news conference. “For now, our full focus is on identifying the cause of the incident.”
TEPCO spokesperson Takashi Kobayashi told AFP that the alarm triggered an investigation into malfunctioning electrical equipment. “Once it became clear the issue would take time to fix, we decided to reinsert the control rods in a planned manner,” he said, emphasizing that the reactor remains stable and “there is no radioactive impact outside the plant.”
Control rods, which regulate the nuclear chain reaction, can accelerate or halt the process depending on their position within the reactor core.
The restart, originally planned for Tuesday, had already been delayed after a separate technical issue related to the removal of control rods was detected over the weekend. TEPCO said that problem was resolved by Sunday.
Kashiwazaki-Kariwa is the world’s largest nuclear power plant by potential capacity, though only one of its seven reactors was being restarted. The facility was shut down following Japan’s 2011 nuclear phase-out, triggered by the Fukushima Daiichi disaster caused by a massive earthquake and tsunami.
Japan, a resource-poor nation, is now seeking to revive nuclear energy to reduce fossil fuel dependency, achieve carbon neutrality by 2050, and meet rising electricity demand driven by technologies such as artificial intelligence.
This is the first TEPCO-operated reactor to restart since 2011. The company is also overseeing the decommissioning of the Fukushima Daiichi plant.
Public opinion in Niigata remains sharply divided. A September survey found that around 60% of residents oppose the restart, while 37% support it.
“It’s Tokyo’s electricity that comes from 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-restart groups submitted a petition to TEPCO and Japan’s Nuclear Regulation Authority, signed by nearly 40,000 people. They highlighted that the plant sits on an active seismic fault zone and recalled a strong earthquake in 2007.