Japan’s Nuclear Power Targets from Impossible (2030) to Hardly Achievable (2040)

in Japanese

Three new developments

Over the past year, three major events have impacted the Japanese nuclear power sector. These developments have both positive and negative implications for the outlook for nuclear power.

Positive points:

• On April 16, 2026, Kashiwazaki Kariwa-6 (1,356 megawatts (MW)), owned by Tokyo Electric Power Company (TEPCO), finally resumed commercial operation after a series of technical problems over the past few months.
• On July 30, 2025, the Nuclear Regulation Authority (NRA) approved the restart of Tomari-3 (912 MW), owned by Hokkaido Electric Power Company. The restart of this reactor is expected as early as possible in 2027 (for its scenarios, REI assumes from FY 2027). This reactor is the youngest in Japan, aged only 16 years.

Negative point:

• On January 14, 2026, the NRA ordered a pause in the safety review of Hamaoka-3 & -4 (1,100 MW and 1,137 MW, respectively), citing a loss of confidence following Chubu Electric Power Company’s admission and confirmation of falsified seismic resistance data.

In Japan, as of April 16, 2026, there were a total of 36 nuclear reactors with a total capacity of 37.2 gigawatts (GW). Of these reactors, 33 were built (33.1 GW), with an average age of 35 years, and 3 were under construction (4.1 GW). Both existing reactors and those under construction face various situations [Chart 1].

Chart 1: Japan – Current Status of Nuclear Reactors, as of April 16, 2026

The FY 2030 target is unattainable, and the FY 2040 target is highly challenging

The four different scenarios developed by REI (see Appendix) present distinct trajectories for nuclear power capacity in operation from FY 2026 to FY 2050 [Chart 2 and Table 1].

Regarding reactor lifespan and its extensions, it is important to note that, in this column, in accordance with international practices (i.e., International Atomic Energy Agency frameworks), the reactor age includes periods of long-term outage. This approach differs from that of Japan, where periods of long-term outage of reactors due to external factors are not taken into account in the age calculation. This controversial approach is unique in the world.

The capacity projections for FY 2041 to FY 2050 are provided for information purposes only, as this column focuses on targets for FY 2030 and FY 2040. They show that, regardless of the assumptions made regarding reactor lifetime extensions in the various scenarios, a wave of reactor closures is projected during the FY 2040s.

Chart 2: Japan – Nuclear Power Capacity in Operation, Projections FY 2026-FY 2050

For reactors without a clearly defined start/restart date, the following assumptions have been made based on current developments:

• Reactors under construction that have applied to start: According to Chugoku Electric Power Company (Shimane-3 (1,373 MW)) and J-POWER (Ohma (1,383 MW)), given the progress of commissioning works and the completion of safety reviews, these reactors could be operational in FY 2030 and FY 2031, respectively. [High and Maximum scenarios]
• Reactors that have applied to restart: Ongoing safety reviews, monitored by BloombergNEF, indicate that these reactors could be operational around FY 2035. For these reactors, the resumption of commercial operation is assumed from FY 2035. [High and Maximum scenarios]
• Reactors that have not applied to restart: To date, the total duration of the safety review process for all reactors that have applied to restart is estimated at nearly 14 years on average. This estimate is based on the actual restart dates of restarted reactors, operator announcements regarding reactors whose restart has been approved, and BloombergNEF’s restart forecasts for reactors for which a restart application has been submitted. For these inactive reactors, the resumption of commercial operation is assumed from FY 2040. This assumption is optimistic and requires immediate action. [Maximum scenario]

Table 1: Explanations Supporting the Nuclear Power Capacity Projections in each Scenario

Then, future shares of nuclear power are estimated using the Japanese government’s total electricity generation projections: 934 terawatt-hours (TWh) in FY 2030 and 1,100-1,200 TWh in FY 2040 [Chart 3].

Chart 3: Japan – Nuclear Power in Electricity Mix, Projections VS. Targets FY 2030 & FY 2040

In the Maximum scenario, it is possible to achieve the government’s nuclear power target of 20% for FY 2040, but not that of 20-22% for FY 2030. In this scenario, the FY 2040 target can be achieved thanks to the assumptions that the reactors which are the least likely to restart (i.e., the existing inactive reactors, as well as Hamaoka-3 and -4, Shika-2 and Tsuruga-2) and to start (i.e., TEPCO's Higashidori-1 (1,385 MW), whose construction has been halted and whose commercial commissioning in FY 2040 is very uncertain) will be progressively brought into service in FY 2035 and FY 2040.

This scenario is particularly ambitious because it also assumes that all reactors will be allowed to operate beyond 60 years (for reference, the current world record is 56 years, held by Beznau-1 (380 MW) in Switzerland) and to operate at a very high-capacity factor of 85% (compared to 73.7% between 2020 and 2024).

In all the other scenarios, the government’s targets for FY 2030 and FY 2040 are not met, even in the High scenario. In this scenario, this is due to an insufficient number of reactor restarts.

In the more realistic Medium and Low scenarios, other problems arise, including a lack of new reactor starts, less favorable assumptions regarding lifetime extensions (i.e., maximum 20 years) and capacity factors (i.e., 70-75%). In both scenarios, a strict 60-year lifespan is set for reactors (including long-term outage). This is partly because no reactor in the world has ever operated for more than 60 years. Furthermore, the International Atomic Energy Agency states that no reactor is immune to the effects of aging, even during an outage.

This conclusion is problematic because it means that it is already possible to predict that Japan will suffer from a significant lack of decarbonized electricity unless renewable energy (RE) exceeds the government’s targets of 36-38% for FY 2030 and 40-50% for FY 2040 (compared to 23.0% in FY 2024).

In Japan, RE also faces its own challenges (e.g., power generation costs, social acceptance, integration into power system operations…). However, given its significant and still under-exploited potential, renewable energy remains better positioned than nuclear power to reduce the country’s heavy dependence on imported fossil fuels. This is why the Japanese government should strengthen its policy for promoting RE instead of hindering it.

This need is all the more urgent in light of the international conflict in the Middle East, which threatens a significant portion of global oil and gas supplies (31% and 18%, respectively), and the increasingly serious effects of climate change.

 

Appendix

Making projections for nuclear power in Japan is a difficult task due to the different circumstances that each reactor must face.

To better understand this uncertainty, four scenarios are developed in this column: “Low”, “Medium”, “High”, and “Maximum”. Each scenario describes a possible evolution based on a wide range of assumptions.

Japan – Scenarios and Assumptions for Nuclear Power Projections