Japan’s nuclear power market is moving from a reactor-restart story toward a broader industrial rebuilding cycle as the country seeks to improve energy security, reduce dependence on imported fossil fuels and increase low-carbon electricity generation.
GlobalData estimates Japan generated 101.0 TWh of nuclear electricity in 2025 and forecasts output to rise to 123.3 TWh by 2035. At the same time, Japan is targeting nuclear power at around 20 percent to 22 percent of electricity generation.
Assuming total electricity demand of approximately 1,050 TWh, a 20 percent nuclear share would require about 210 TWh annually, while a 22 percent share would need around 231 TWh. Compared with 2025 nuclear generation of 101.0 TWh, that implies an analytical generation gap of roughly 109 TWh to 130 TWh.
The scale of that gap means Japan will need more than regulatory approvals. Higher reactor utilization, life-extension investment, manufacturing capacity, engineering expertise, fuel-cycle infrastructure and radioactive-waste solutions will all be critical.
Japan Has 33 Reactors Representing 33.1 GW
Japan has approximately 397.34 GW of total installed power capacity, including a baseline nuclear fleet of 33 reactors with about 33.1 GW of capacity.
By 2025, 15 reactors representing approximately 14.6 GW had restarted. Another three reactors had received regulatory approval and were moving toward operational readiness, while six remained under active safety review.
A further eight reactors remained inactive because of regulatory, seismic, technical or other uncertainties.
Japan’s average nuclear capacity factor recovered to approximately 33.6 percent in 2025, its highest level since 2015. While this marks meaningful progress, utilization remains well below the levels required to maximize output from the existing fleet.
70-80% Capacity Factors Could Transform Nuclear Generation
Capacity factor is one of the most important variables in Japan’s nuclear recovery.
If 30 reactors operated at a 70 percent capacity factor, they could generate approximately 184 TWh annually. Increasing utilization to 80 percent would lift output to around 211 TWh.
If all 33 reactors were operating, annual nuclear generation could reach approximately 203 TWh at a 70 percent capacity factor and around 232 TWh at 80 percent.
These scenarios demonstrate why Japan cannot focus solely on restarting more reactors. Maintenance efficiency, outage management, fuel availability and component reliability will determine how many terawatt-hours the fleet actually delivers.
Kashiwazaki-Kariwa Unit 6 Marks Major TEPCO Milestone
Tokyo Electric Power Company Holdings is central to Japan’s nuclear comeback through the Kashiwazaki-Kariwa Nuclear Power Station.
The seven-unit complex has approximately 8.2 GW of nuclear capacity, making it one of the largest nuclear sites globally.
Kashiwazaki-Kariwa Unit 6, rated at 1,356 MW, restarted in January 2026 and entered commercial operation in April 2026. It represents the first TEPCO reactor to return to commercial operation since the Fukushima Daiichi accident.
Unit 7 is also rated at approximately 1,356 MW. Together, Units 6 and 7 represent around 2.7 GW of potential generation capacity.
Successful sustained operation at Kashiwazaki-Kariwa could strengthen confidence in Japan’s broader restart pipeline, while technical or regulatory setbacks would reinforce concerns about the complexity of returning dormant nuclear assets to service.
Tomari, Onagawa and Shimane Add to Restart Pipeline
Other utilities are also advancing reactors through Japan’s post-Fukushima safety process.
Hokkaido Electric’s Tomari-3 has 912 MW of capacity, while Tohoku Electric’s Onagawa-2 provides 825 MW.
Chugoku Electric’s Shimane-2 and restart candidates operated by Kansai Electric, Kyushu Electric and Shikoku Electric broaden the national recovery pipeline.
Shikoku Electric’s Ikata-3 has 890 MW of capacity, while Kyushu Electric continues to operate its Sendai and Genkai nuclear plants.
Chubu Electric’s Hamaoka Units 3 and 4 remain affected by regulatory and seismic issues, illustrating why nominal nuclear capacity cannot automatically be treated as commercially available generation.
Aging Reactors Create Long-Term Life-Extension Market
Japan’s nuclear revival is also creating a significant market for plant life extension.
Kansai Electric operates major nuclear assets at Takahama, Ohi and Mihama. Mihama-3 and Takahama Units 1 and 2 have passed the 50-year operating threshold, increasing demand for inspections, replacement components, safety upgrades and long-term asset-management services.
This extends the commercial opportunity beyond the restart phase.
Older reactors require recurring spending on pumps, valves, electrical equipment, cooling systems, instrumentation, control technologies, turbines, generators and structural inspections.
Post-Fukushima requirements further increase demand for emergency power systems, seismic protection, containment improvements, hydrogen-management technologies and severe-accident mitigation equipment.
Japan Steel Works to Double Nuclear Production by FY2028
Manufacturing capacity is emerging as another strategic constraint.
Japan Steel Works plans to double nuclear-product production capacity by FY2028, reflecting the growing requirement for nuclear-grade components as existing reactors restart and advanced nuclear projects progress.
Nuclear manufacturing has unusually long lead times and strict certification requirements, making rapid supply-chain expansion difficult.
This creates opportunities across reactor components, turbines, generators, cooling technologies, electrical systems, instrumentation and other safety-critical equipment.
A larger operating fleet will also require greater availability of specialist engineering and inspection capacity.
Engineering Talent Could Become a Nuclear Bottleneck
Japan’s nuclear expansion will depend not only on factories but also on skilled engineers.
Restart and life-extension programs require expertise in seismic analysis, safety assessment, regulatory documentation, plant inspection and modernization.
If multiple utilities pursue projects simultaneously, demand for nuclear engineers, inspectors and safety specialists could increase faster than Japan can expand its workforce.
That makes human-capital development a potentially significant constraint through the 2030s.
JPY 5 Trillion Framework Supports Advanced Nuclear and SMRs
Japan’s broader nuclear investment framework is estimated at approximately JPY 5 trillion through 2040, covering advanced reactors, small modular reactors and nuclear supply-chain reconstruction.
The strategy creates a longer-term market beyond existing-reactor restarts.
Mitsubishi Heavy Industries is positioned across nuclear equipment, engineering, maintenance and advanced-reactor development.
Hitachi is also expanding through Hitachi GE Vernova Nuclear Energy and the approximately 300 MW BWRX-300 small modular reactor.
These technologies could give Japan another avenue to rebuild nuclear engineering and manufacturing capabilities while competing in the emerging international SMR market.
Spent Fuel Could Limit Reactor Utilization
Japan’s nuclear recovery also faces a significant back-end challenge.
The country has accumulated approximately 1,450 tonnes of spent nuclear fuel, while storage pools at some major utilities are already highly utilized.
Some Kansai Electric facilities have reported spent-fuel storage utilization ranging from approximately 59 percent to 95 percent.
Higher nuclear generation will add to this inventory. That creates a direct link between reactor utilization and the availability of storage, transportation, reprocessing and permanent disposal infrastructure.
Without sufficient back-end capacity, nuclear waste management could eventually restrict reactor operations.
Mutsu Offers 3,000 Tonnes of Interim Storage
The Mutsu interim-storage facility can provide approximately 3,000 tonnes of spent-fuel storage capacity.
This gives utilities additional flexibility as on-site storage becomes more constrained.
However, interim storage does not eliminate the need for permanent waste solutions. It primarily provides additional time for Japan to develop reprocessing and geological-disposal infrastructure.
Rokkasho Designed for 800 Tonnes Per Year
The Rokkasho Reprocessing Plant remains central to Japan’s closed nuclear fuel-cycle strategy.
The facility is designed to process approximately 800 tonnes of uranium per year.
Its repeated delays have increased uncertainty over the timing of large-scale spent-fuel reprocessing.
If reactor generation rises significantly while reprocessing capacity remains constrained, the imbalance could put further pressure on storage infrastructure.
Japan therefore needs to synchronize front-end reactor operations with back-end fuel-cycle development.
Permanent Nuclear Waste Disposal Remains Unresolved
Japan still lacks a fully established permanent geological repository for high-level radioactive waste.
Repository development can take decades because it involves geological investigation, environmental review, technical assessment, regulatory approvals, transportation planning and long-term community acceptance.
This timing mismatch is important. Existing reactors can potentially restart within several years, while permanent disposal infrastructure may require much longer.
Without progress on waste policy, spent fuel could become a structural constraint on nuclear generation growth.
Japan Faces 109-130 TWh Gap to 20-22% Nuclear Target
Japan’s policy ambition becomes clearer when translated into annual generation.
At approximately 1,050 TWh of total electricity demand, a 20 percent nuclear share equals roughly 210 TWh, while 22 percent equals approximately 231 TWh.
Against 101.0 TWh generated in 2025, the analytical shortfall is around 109 TWh at the lower end and 130 TWh at the upper end.
These figures are analytical scenarios rather than GlobalData forecasts. Actual requirements will depend on total electricity demand, renewable generation, reactor availability and the future power mix.
Even so, they demonstrate that Japan requires a substantial increase in usable nuclear output.
GlobalData Forecasts 123.3 TWh Nuclear Generation by 2035
GlobalData expects Japan’s nuclear generation to increase from 101.0 TWh in 2025 to 123.3 TWh in 2035.
That represents continued recovery but remains well below the 210-231 TWh implied by a 20-22 percent nuclear share under the assumed 1,050 TWh demand scenario.
The comparison uses different analytical assumptions and should not be treated as a direct forecast gap. However, it underlines the execution challenge facing Japan.
Attaurrahman Ojindaram Saibasan, Power Analyst at GlobalData, said Japan’s technical nuclear recovery is progressing as pre-2011 reactors are requalified and upgraded, but community mistrust, slow safety reviews and unresolved waste-storage decisions remain major barriers.
Japan Nuclear Market Expands Across Entire Value Chain
The commercial opportunity is consequently broader than reactor restarts.
Utilities need to restore generation and increase capacity factors. Manufacturers need to supply safety systems and replacement components. Engineering companies are required for seismic assessment, inspection and regulatory compliance. Advanced-reactor developers are pursuing new technologies, while fuel-cycle companies need to expand storage, reprocessing and waste-management infrastructure.
Japan’s JPY 5 trillion investment framework through 2040, Japan Steel Works’ plan to double nuclear-product capacity by FY2028, the 3,000-tonne Mutsu storage facility, and Rokkasho’s 800-tonne-per-year design capacity demonstrate the industrial scale of the emerging market.
GlobalData believes nationally supported waste-management roadmaps, transparent safety-upgrade programs, phased permitting with community engagement and greater support for SMRs will be critical.
If execution improves, Japan could move closer to its 20-22 percent nuclear generation objective while reducing fossil-fuel imports and emissions. If progress remains slow, thermal generation may need to cover a larger share of electricity demand. Japan’s nuclear comeback will therefore ultimately be measured not by how many reactors receive approval, but by how many reliable TWh of electricity the country can sustainably produce from its 33-reactor, 33.1 GW fleet.
SHAFANA FAZAL
