Japan - World Nuclear Outlook Report
Current operations
Japan had more than 50 operable nuclear reactors at the time of the March 2011 accident at Fukushima, all of which were taken offline, either when the accident occurred or in the months after as they reached maintenance outages. Since then, reactors have been required to undergo restart assessments. Up to July 2026, 15 units have restarted, with 18 operable units still requiring permission to restart, of which 10 units have applied to restart.
Unit 6 of the Kashiwazaki-Kariwa plant restarted commercial operation in April 2026, becoming the first reactor owned by Tokyo Electric Power Company to do so.
Table Jp.1 Nuclear capacity status (as of 31 December 2025)
| Operable reactors | Operable reactors net capacity (MWe) | Operable reactor gross capacity (MWe) | Reactors under construction | Reactors under construction gross capacity (MWe) | Carbon dioxide emissions avoided (cf. coal) (MtCO2) |
|---|---|---|---|---|---|
| 33 | 31,679 | 33,083 | 2 | 2756 | 7479 |
Nuclear policy and outlook
Japan's GX Decarbonization Power Supply Act, passed in May 2023 and in force since June 2025, marks a major shift in the country's energy policy, repositioning nuclear power as a key source of stable, zero-emissions electricity. The Act retains the 40-year operating lifetime limit with a possible 20-year extension, excluding periods when reactors were offline – effectively allowing for operation beyond 60 years.
The 7th Strategic Energy Plan, approved by the Cabinet in February 2025, maintains a nuclear share of around 20% of electricity generation in FY2040, with renewables at 40-50%. It removed the commitment to "reduce dependence on nuclear power as much as possible," which had appeared in every plan since 2014. It also broadened replacement to allow new reactors at other sites owned by the same utility, not only at the site of the retiring unit.
In mid-2026 the Ministry of Economy, Trade and Industry (METI) said it estimated that two-to-five large reactors (about 2.2-5.5 GWe) will need to be replaced by the 2040s to maintain the 20% share, rising to a cumulative 11-14 reactors (about 12.7-16 GWe) by the 2050s. It is the first numerical replacement target set since the Fukushima Daiichi accident.
Three reactors were under construction at the time of the accident. Construction of Shimane 3 and Ohma was suspended in 2011 and resumed in 2012, and both units are now undergoing safety reviews. Construction of Tepco's Higashidori 1, which began in January 2011, remains suspended.
Table Jp.2 Contributions to total capacity projection in 2050
| 60 year operation (MWe) | 80 year operation (MWe) | Currently under construction capacity (MWe) | Planned capacity (MWe) | Proposed capacity (MWe) | Potential capacity (MWe) | Government capacity target (MWe) | Additional capacity* required to meet government target (MWe) | Total capacity (MWe) |
|---|---|---|---|---|---|---|---|---|
| 18447 | 14646 | 2756 | - | 1385 | 37224 | 0 | 37224 | |
| *Capacity additional to operable, under construction, planned, proposed and potential capacities required to meet the government target. | ||||||||
Readiness Assessment
Japan’s strongest attributes are its industrial base, operating experience and regulatory system and its increasingly supportive national policy. Its weaker areas are the absence of a sufficiently firm post-2030 construction programme, although the recent METI draft target for reactor replacement has helped progress this issue.
| Country Category | Restarter |
|---|---|
| Policy Framework Readiness | Moderate-High Japan has a clear and increasingly supportive national policy for maintaining nuclear generation as part of its future energy mix. This is to be achieved by restarting suitable reactors, enabling long-term operation and developing next-generation reactors. |
| Institutional and Infrastructure Readiness | Moderate-High Japan has an experienced regulator, established nuclear legislation, capable utilities, major domestic reactor vendors, a substantial supply chain and extensive operational and research expertise. To achieve its goals it will need to address the long interruption in domestic new construction and the time required for regulatory reviews. |
| Programme & Project Development | Moderate Fifteen reactors have restarted and several units are progressing through long-term operation arrangements. However, many reactors remain suspended: Ohma has no firm operation date, Shimane 3 remains incomplete, and plans for replacement reactors and SMRs are nascent. |
| Target Achievability | Moderate Achieving around 20% nuclear generation in 2040 is plausible but not assured. It depends on further restarts, high operating performance, extensive operating lifetime extensions and the timely commissioning of additional capacity. Delays to restarts, reactor retirements and the absence of firm replacement projects will need to be addressed to reduce the delivery risk. |
