Officials Are Investigating an Incident That Halted Operations at the World’s Largest Nuclear Plant

Micah Hanks·
nuclear power
(Image Credit: Tokyo Electric Power Co)

Welcome to this edition of The Intelligence Brief… This week, the long-anticipated restart of the world’s largest nuclear power plant in Japan was abruptly suspended after an unexpected incident halted operations at the Kashiwazaki-Kariwa-6 reactor just hours after it came back online. In our analysis, we’ll be looking at 1) what officials say triggered alarms during the reactor’s startup and why operations were paused despite assurances the unit remains stable, 2) how the incident revives lingering safety concerns rooted in the shadow of the 2011 Fukushima disaster, 3) why local opposition and technical setbacks continue to complicate Japan’s nuclear revival, and 4) how delays at Kashiwazaki-Kariwa could affect Japan’s broader push to restore nuclear capacity while pursuing its long-term net-zero emissions goals.

Quote of the Week

“The core of the nuclear power business is ensuring safety above all else, and the understanding of local residents is a prerequisite.”

– Tatsuya Matoba, TEPCO Spokesperson

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RECENT NEWS from The Debrief

Incident at the World’s Largest Nuclear Plant

This week, the widely anticipated resumption of operations at the world’s largest nuclear power plant took an unexpected turn, as the restart of Unit 6 at Japan’s Kashiwazaki Kariwa nuclear power station was suspended.

The suspension occurred within hours of the facility restarting, following an incident that officials with the Tokyo Electric Power Company (TEPCO) said they are currently investigating.

Although details are still forthcoming, the incident reportedly involved an alarm that was triggered during the reactor’s start-up process. Although officials have said the reactor is in stable condition, the situation added a new layer of tension to startup procedures at Kashiwazaki Kariwa-6, which has remained offline since the Fukushima disaster in 2011.

In the Shadow of Fukushima

Located in Western Japan, the Kashiwazaki Kariwa nuclear power station is officially the world’s single largest nuclear plant.

In 1996, the facility’s Unit 6, a 1315-megawatt boiling water reactor unit, officially began its initial commercial operations. Following the Fukushima disaster, the facility has remained offline, and its resumption to service would mark 15 units that have officially been restored to service since that time.

In the aftermath of the 2011 incident, which resulted from a 9.0 magnitude earthquake that triggered the historic meltdown at the Fukushima plant, Japan took all 54 of its reactors offline.

Concerns over the resulting radiation leakage prompted the evacuation of more than 150,000 Japanese residents, many of whom elected not to return. Officials maintain that the area is under no danger resulting from radiation contamination.

Unit 6 is Stable… For Now

After restarting Unit 6 on Wednesday—already one day later than originally scheduled—officials reported that operations had to be suspended, although Takashi Kobayashi, a spokesperson with Tokyo Electric Power Company, said the facility was in stable condition.

On Thursday, Kobayashi confirmed there was “no radioactive impact outside” the facility, and that the reactor had merely experienced a technical issue, which reportedly involved a malfunction related to control rods at the facility.

Based on current timelines, officials with Tokyo Electric Power Company now expect the facility to resume commercial operations sometime in February.

“Incident” Under Investigation

As far as what triggered alarms that prompted officials to halt operations at the facility, Kobayashi has said that the incident is presently still under investigation, and few details have been made available about its possible cause.

According to the BBC, although Unit 6 was cleared to resume operations, many residents have expressed concerns about its safety, and this week’s unexpected problems will likely do little to quell concerns about safety in the lingering shadow of the Fukushima disaster.

Even once Unit 6 goes online, Kashiwazaki-Kariwa will still be operating well below its original operating capacity. According to current timelines, Unit 7 is not anticipated to resume operation until at least 2030, and five other units at the facility may remain offline indefinitely.

Ultimately, Japan remains committed to its aspiration to achieve net zero emissions by the middle of the century, a goal which was significantly hampered by the Fukushima disaster, although in the last decade nearly half of its 33 operable reactors have resumed operation.

That concludes this week’s installment of The Intelligence Brief. You can read past editions of our newsletter at our website, or if you found this installment online, don’t forget to subscribe and get future email editions from us here. Also, if you have a tip or other information you’d like to send along directly to me, you can email me at micah [@] thedebrief [dot] org, or reach me on X: @MicahHanks.

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