Japan has decided to revise its nuclear energy policy guidelines to include a target of “rebuilding” 2-5 nuclear power reactors by the 2040s. In Japan’s nuclear energy guidelines, “rebuild” (often translated as “replace” or “reconstruct”) means constructing brand-new, next-generation reactors directly within the sites of existing, decommissioned power plants. Instead of building entirely new nuclear facilities in new locations, the government is initially replacing retired units with modern ones.
The decision was adopted at a meeting of relevant Cabinet ministers led by Prime Minister Sanae Takaichi. “We will move forward with policies to ensure investment in nuclear power plants,” Prime Minister Sanae Takaichi said at the meeting, suggesting that the government will also promote programs to nurture human resources.
The aim is to mitigate a projected power supply shortage in the 2040s due to the decommissioning of ageing reactors that have been in operation for 60 years and to address increased demand driven by the surge of AI data centres and advanced manufacturing.
The target for the 2050s is to expand the replacement initiative to build an additional nine reactors, bringing the cumulative total to 11 to 14 new reactors. The final 14-plant fleet is projected to supply 16 GWe of new capacity. The goal is to double nuclear power’s current share in the national grid, aiming for it to supply roughly 20% of Japan’s electricity by fiscal year 2040, up from roughly 8.5% in 2023. Reliance on coal, natural gas, and oil will be reduced from the current 60–70% down to 30–40%.
Anticipating possible opposition to the plan, Industry Minister Ryosei Akazawa announced a revised framework to advance surveys for high-level radioactive waste final disposal sites while offering higher relief incentives to local municipalities. More than 40,000 public comments were submitted opposing the expansion, fuelled by persistent post-Fukushima trust issues and recent seismic safety scandals at other regional plants.
The plan could face other obstacles. A recent Nikkei Asia assessment revealed that 70% of companies in Japan’s nuclear sector face critical difficulties recruiting specialised staff and engineers. The 20% target requires bringing Japan’s broader idle fleet back online. Out of 33 operable units, only 15 have cleared post-Fukushima safety standards to resume operations.
The government is shifting funding through the New Energy & Industrial Technology Development Organisation (NEDO) to speed up the integration of small modular reactors (SMRs) and advanced safety designs. The revised guidelines preserve the safe decommissioning of Tokyo Electric Power Company’s (Tepco’s) Fukushima Daiichi NPP as the state’s highest structural priority.
The government has not yet published an official, definitive list identifying specific reactor sites for the 2040s rebuild strategy. However, according to the Ministry of Economy, Trade and Industry (METI) and industry utility opinion, specific locations have emerged as the clear priorities based on their operational history, recent restarts, and active site surveying.
The selection process for candidate sites automatically favours those that meet three criteria:
- Sites housing reactors built in the 1970s and 1980s that will hit their strict 60-year operational limits by the 2040s;
- Plants where utilities have already spent billions upgrading seawalls, backup generators, and seismic defences to pass NRA’s modern safety protocols; and
- Areas where local governors and town councils are receptive to the newly revised, higher government relief incentives for hosting nuclear infrastructure and waste surveys.
Fukui Prefecture (the “Nuclear Coast”) is the frontrunner for early rebuilds due to its high concentration of existing reactors and relatively cooperative local municipalities. Kansai Electric Power Co’s Mihama NPP is currently the most prioritised site for the new rollout. Kansai has already revived and initiated targeted geological and topographical on-site surveys to prepare for the construction of a next-generation reactor. The utility is actively planning to deploy the SRZ-1200, an advanced 1,200 MWe light-water reactor developed by Mitsubishi Heavy Industries designed with enhanced safety features. Units 1 and 2 at Mihama have already been permanently shut down and are undergoing decommissioning, providing an ideal open footprint.
Kansai’s Takahama NPP, also in Fukui Prefecture, is also heavily prioritised for long-term planning because its units were among the first ageing reactors successfully restarted under the strict post-Fukushima safety standards. However, Takahama houses two units that are among the oldest in the country and will reach their maximum 60-year operational lifetimes before 2040.
Sendai NPP in Kagoshima Prefecture is also widely cited in government strategy drafts as a primary candidate. Kyushu Electric has announced formal considerations for next-generation innovative reactors to meet surging regional grid demands, heavily driven by new local AI data centres. The site has a pre-existing blueprint originally intended for a third unit (Sendai-3) that was abandoned after the 2011 Fukushima disaster, meaning substantial preliminary siting work is already complete.
In Hokkaido Prefecture, Hokkaido Electric Power Co’s Tomari is another candidate. Following the Nuclear Regulation Authority’s (NRA’s) safety approval of Tomari unit 3 in July 2025 (targeted for full commercial restart by 2027), this site has risen significantly in priority. As the youngest operable reactor site in the country, its existing grid connections and updated safety infrastructure make it highly viable for next-generation expansion.
In Niigata Prefecture, Tepco’s seven-unit Kashiwazaki-Kariwa NPP, as one of the largest nuclear plants in the world, is critically important to Japan’s grid. The commercial restart of unit 6 in April represents a regulatory milestone for Tepco. Because the infrastructure here is massive and capable of handling high-capacity outputs, it is technically an elite candidate for future co-located replacement reactors. However, unlike other Japanese utilities permitted to build new reactors, Tepco is currently restricted solely to restarting existing assets due to trust issues and financial burdens from the Fukushima cleanup.
