Japan has brought the world’s largest nuclear power station back to life, restarting one of the Kashiwazaki-Kariwa reactors after a shutdown that stretched across the post-Fukushima era. The move signals a decisive, and deeply contested, turn back toward atomic power as the country wrestles with energy security, climate targets, and the lingering trauma of 2011.
The restart at Kashiwazaki-Kariwa is not just a technical milestone, it is a political and emotional one, exposing a sharp divide between leaders who see nuclear energy as indispensable and residents who remain, in their own words, “anxious and fearful” about what happens if something goes wrong again.
The giant on Japan’s northwest coast powers back up
On the coast of Niigata prefecture, the complex officially known as The Kashiwazaki Kariwa Nuclear Power Plant has long held the title of the world’s largest nuclear facility by installed capacity, with seven reactors that once delivered 8.2 gigawatts when fully operational. After years in cold storage, Japan has now restarted operations at this vast site, beginning with a single unit that serves as a test case for the rest of the fleet. The decision follows a political green light from the Niigata assembly, which earlier backed the return of the Niigata site despite its association with the operator that ran the doomed Fukushima plant.
The operator, Tokyo Electric Power Company, or TEPCO, has framed the restart as a carefully staged process that begins with Kashiwazaki Kariwa Unit 6 and could eventually extend to other reactors on site. Technical accounts describe how TEPCO has brought Kashiwazaki Kariwa Unit 6 back online first, with plans to restart Unit 7 by 2030 while leaving the fate of the remaining five units undecided. Video explainers circulating in Japan underline that this single complex, once fully restored, could again rank as the largest nuclear power plant in the world by installed capacity, a scale that makes every operational decision at Kashiwazaki-Kariwa globally significant.
From Fukushima’s shadow to a contested nuclear comeback
The symbolism of TEPCO restarting a reactor for the first time since the Fukushima disaster is impossible to ignore. The same company that oversaw the 2011 meltdown has now reactivated one of seven reactors at Kashiwazaki Kariwa, a plant that itself has been shut since the Fukushima crisis exposed deep flaws in Japan’s nuclear oversight. The Kashiwazaki-Kariwa reactor has remained offline since that 2011 Fukushima disaster, a pause that turned the site into a symbol of national hesitation about nuclear power, as detailed in regional coverage of Fukushima and its aftermath.
Japan’s political leadership has steadily shifted from hesitation to advocacy. Prime Minister Prime Minister Sanae is pushing for the construction of new reactors, particularly new-generation and small modular designs, arguing that nuclear power is essential for decarbonization and energy security. That national pivot has been described as a Watershed moment in Japan’s energy policy, with the Niigata assembly’s vote to restart Kashiwazaki-Kariwa marking a concrete step in that direction.
Safety upgrades, stricter rules and a 50-foot wall
Regulators have not simply flipped a switch back to 2010. Under Japan’s stricter nuclear regulations, operators are required to build dedicated anti terrorism facilities, known as specific safety facilities, to protect reactors from deliberate attacks and severe accidents. TEPCO has had to bring Kashiwazaki-Kariwa into line with these Under Japan requirements, a process that included addressing earlier security lapses that led regulators to suspend the plant’s operations. Technical assessments of the restart note that TEPCO has worked to rectify those issues, with World Nuclear News style reporting pointing to specific deficiencies that the company says have since been rectified.
Physical defenses have also been dramatically reinforced. The Kashiwazaki-Kariwa plant has been fitted with a 15-metre-high, 50-foot tsunami wall, a concrete reminder of the waves that overwhelmed Fukushima’s sea defenses. Officials argue that this barrier, combined with new backup power systems and flood protections, makes a repeat of 2011 far less likely. TEPCO has also highlighted its investment in additional safety systems at TEPCO facilities, while national energy plans emphasize that Japan’s Kashiwazaki-Kariwa nuclear plant, described as the world’s largest by capacity, is central to meeting climate goals, as reflected in policy discussions around Japan’s Kashiwazaki Kariwa nuclear plant and its role in reducing fossil fuel use.
Local fear, national need and the politics of risk
For residents around Kashiwazaki and Kariwa, the restart is as much an emotional event as a technical one. Local reporting has captured voices describing themselves as Anxious and fearful, worried that TEPCO’s track record and the plant’s sheer size magnify the consequences of any failure. The Kashiwazaki-Kariwa plant has been at the center of protests and legal challenges for years, with opponents arguing that no amount of engineering can fully erase the risk of another catastrophic accident. Those concerns are sharpened by the memory that TEPCO also ran the Fukushima site, a link that is repeatedly highlighted in accounts of how the Kashiwazaki Kariwa reactor has been shut down since the Fukushima disaster, described as the worst nuclear accident since Chernobyl.
National planners, however, see a different risk: the danger of relying too heavily on imported fossil fuels in a volatile world. Before Fukushima, nuclear plants supplied roughly a third of Japan‘s electricity, a share that collapsed when reactors were idled and utilities turned to liquefied natural gas and coal. Policy documents now frame the restart of Kashiwazaki-Kariwa as part of a broader effort to restore nuclear’s contribution to the grid and cut emissions, with some analyses noting that Japan’s nuclear share had fallen to around 8.5% in 2023–24 before the new wave of restarts, a figure cited in discussions of 8.5%. That tension between local fear and national need is now playing out in Niigata’s coastal towns, where jobs and tax revenue from the plant sit uneasily alongside evacuation drills and emergency sirens.
A milestone restart, an immediate pause and what comes next
The restart itself has already underscored how fragile public trust remains. Within a day of achieving a milestone reboot at Kashiwazaki-Kariwa, Tokyo Electric Power Co., described as Japan’s largest utility, suspended the process after an issue that required further checks. Energy industry reports note that TEPCO paused the nuclear reactor reboot shortly after the celebrated restart, even as the company insisted that work to ultimately restart the plant would continue, a sequence captured in coverage that cites By Bloomberg and describes the pause as a temporary setback rather than a reversal. Financial and energy market analyses have echoed that framing, with headlines such as Tepco Pauses Nuclear emphasizing both the symbolic importance of the restart and the operational caution that followed.
Even with that pause, the direction of travel is clear. TEPCO has already restarted one reactor at Tepco’s Kashiwazaki-Kariwa site and plans to bring more units back over the coming years, while national leaders talk openly about building new-generation reactors and small modular units. Detailed accounts of the restart describe how Tokyo Electric Power Company has brought a unit at Kashiwazaki Kariwa Nuc back online, while technical briefings stress that the plant’s earlier security problems have been addressed. For global observers, the restart of the world’s largest nuclear power station is a test of whether a country that lived through one of history’s worst nuclear disasters can rebuild confidence in the atom, or whether every new alarm at Kashiwazaki and Kariwa will reopen the wounds of Fukushima.
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