Japan is moving toward restarting the Kashiwazaki-Kariwa nuclear power station, the world’s largest by capacity. The move could change the country’s energy policy, which relies on atomic power to tackle high fuel costs, boost energy security, and reduce carbon emissions.
The nuclear plant is run by Tokyo Electric Power Company (TEPCO), and the restart of its biggest units, No. 6 and No. 7, together producing about 2,710 megawatts (MW), could happen soon, if regulators and local authorities approve.
It is the governor of Niigata prefecture who moves to approve the restart of the Kashiwazaki-Kariwa facility. Hideyo Hanazumi plans to hold a press conference to announce his decision and said he will consult with the prefectural assembly. If the assembly also agrees, the restart will be officially authorized. He said during a media briefing:
“I would like to make a decision and express it soon.”
A Long Road Back: Why Japan’s Nuclear Revival Matters
After Fukushima in 2011, Japan shut down nearly all its reactors, and restarting them has been slow. By late 2024, only 14 reactors had started back up under the stricter post-Fukushima rules.
Kashiwazaki-Kariwa, also called KK, has a total capacity of 8,212 MW, making it the largest nuclear power plant in the world. The facility has mostly sat unused since 2012. This happened after safety worries and stricter rules came in after the 2011 Fukushima disaster.
In December, regulators lifted a de facto ban that had blocked TEPCO from loading fresh nuclear fuel into the plant. The company has done safety inspections and is now seeking approval from Niigata Prefecture. This includes getting the governor’s okay, as they have a lot of influence over the decision.
If approved, restarting even part of Kashiwazaki-Kariwa could dramatically boost Japan’s nuclear output. For TEPCO, this move may lower operating costs, reduce dependence on costly imported fuels, and improve its long-term financial outlook.
Japan’s Nuclear Comeback: The Bigger Picture
Nuclear’s share in Japan’s electricity mix has begun to rise, per the ISEP data. In fiscal year 2023, nuclear energy made up 8.5% of the country’s power generation. It is the highest level since before Fukushima. Fossil fuels, especially LNG and coal, still supply the bulk of power.
The country still has far to go. Many reactors remain offline as utility firms seek regulatory approval and local consent. The largest plant, Kashiwazaki-Kariwa, could add back several gigawatts if its units restart.
Policy now backs a larger nuclear role. The government’s strategic energy plan targets roughly 20% nuclear by 2040, alongside a big push for renewables (40–50%). These goals aim to cut fuel import bills and lower emissions, but they will require many more restarts, life extensions, or new builds.
The commercial case for more nuclear in Japan rests on several factors. Restarted reactors reduce costly LNG use and help utilities stabilize generation costs. They also provide steady, low-carbon baseload power that complements intermittent renewables.
On the other hand, safety upgrades, decommissioning risks, and local opposition impose large financial and political costs.
In short, Japan’s nuclear comeback is real but cautious. Progress relies on a few key factors:
- Regulatory approvals,
- Local consent, ongoing safety investments, and
- Nuclear’s ability to compete with cheaper renewables and storage as they grow.
Small but Mighty: Japan’s Growing Interests in SMR
Japan is also studying the use of Small Modular Reactors, or SMRs, as part of its longer-term energy plan. These reactors are smaller and can be built in factories, which may reduce costs and construction time. They could help Japan add more nuclear power without the long delays that come with large plants.
Several Japanese companies are already working with international partners to develop SMR designs. IHI, a leading equipment maker, is working with a U.S. firm, NuScale Power, on modular reactor technology. They have built full-scale mock-ups to test their engineering systems.
Chubu Electric Power, one of the country’s major utilities, has also announced plans to invest in SMR projects at home and overseas. These steps show rising industry interest in this new type of reactor.
Even with this momentum, Japan’s SMR plans are still at an early stage. The government has not yet completed a full regulatory framework for these reactors. Safety rules, design standards, and licensing pathways still need more work before construction can begin.
- Japan faces key economic questions. Can SMRs compete with renewables, large reactors, and imported fuels?
Because of these factors, experts expect SMRs to grow slowly. The Asian country may first use them for research or for exports before they appear in domestic power grids.
Still, as the country looks for low-carbon energy and more stable power supplies, SMRs are becoming part of the national discussion about the future of nuclear power.
Hurdles Ahead: Safety, Costs, and Local Concerns
Even with regulatory and political momentum, restarting Kashiwazaki-Kariwa faces hurdles. Local consent remains a key issue: the governor needs the nod of the prefectural assembly.
Safety is a major concern. TEPCO must run the plant under the tougher standards imposed after Fukushima. For residents near the plant, the disaster’s memory is still strong. This leads to local resistance in some communities.
There are financial risks, too. Restarting nuclear plants requires huge investments in safety upgrades, regulatory compliance, and community relations. If the market for electricity or nuclear power shifts, these costs could pose a burden.
Strategic Impact on Japan’s Energy Market
If put back online, Kashiwazaki-Kariwa could play a key role in lowering Japan’s import bill for liquefied natural gas (LNG). Japan is one of the world’s largest LNG importers, and atomic power offers a way to reduce its reliance on volatile markets.
More nuclear generation could also support Japan’s climate goals. The government’s energy roadmap targets a big increase in nuclear while also expanding renewables, aiming for a 40–50% renewable share by 2040. In that plan, nuclear provides a stable, carbon-free “baseload” to complement fluctuating solar and wind power.
The restart could also reshape investor sentiment. Utilities, financial institutions, and even global energy analysts are watching closely. A strong comeback of large nuclear power could show faith in Japan’s atomic revival. This might also encourage long-term investments in its nuclear industry.
Why the Restart is Significant Globally
Japan’s potential restart of the world’s largest nuclear plant comes at a moment when many countries are rethinking nuclear power. Rising energy prices, geopolitical instability, and stronger climate targets make nuclear more attractive. A revival in Japan could influence other nations to reconsider or expand their own nuclear programs.
For TEPCO, a successful restart strengthens its case for nuclear as a core part of its business. For the region, it offers more stable energy, local economic support, and lower emissions. And for Japan, it could signal that the nuclear sector is fully back in its long-term energy mix.
If the governor of Niigata approves the restart as expected, Japan may very soon add a major source of clean, reliable power — and a potent symbol of its atomic revival.