Japan’s FY 2030 & FY 2040 Nuclear Power Targets Are Probably Out of Reach

in Japanese

On 18 February 2025, the Japanese government approved the 7^th Strategic Energy Plan (SEP), showing the basic directions of the country’s energy policies. This Plan vows to make the maximum use of nuclear power, unlike the previous 6^th SEP of 2021 which committed to reduce dependence on nuclear power as much as possible. Regardless of the rhetoric, both plans set excessively ambitious shares for nuclear power in electricity generation: 20-22% in fiscal year (FY) 2030 (6^th SEP) and 20% in FY 2040 (7^th SEP). Demonstrating the reality of this affirmation is the objective of this column. For this purpose, new projections are provided. These projections include all the latest developments regarding the status of nuclear reactors, and explore four different scenarios: “Low”, “Medium”, “High”, and “Maximum” based on a wide range of transparent assumptions. It is found that both the FY 2030 & FY 2040 targets are achievable only in the extreme “Maximum” scenario. Instead, in the reasonable “Medium” scenario, nuclear power accounts for 12% of Japan’s electricity generation in FY 2030 and 7-8% in FY 2040.

61% of Nuclear Reactors Are Not Ready for Operation

In Japan, as of 14 March 2025, there was a total of 36 nuclear reactors with a total capacity of 37 gigawatts (GW) (Chart 1). Of these reactors, 33 were existing (33 GW) and 3 were under construction (4 GW). Besides these ones, 26 reactors are in the process of decommissioning. This preliminary information is, however, insufficient to precisely grasp the diverse realities of the Japanese reactor fleet.

Chart 1: Japan – Current Status of Nuclear Reactors, as of 14 March 2025

Of the 33 existing reactors, only 14 reactors (13 GW) have restarted commercial operation following the implementation of more stringent safety standards, consecutive to the Fukushima Daiichi nuclear accident in March 2011. Half of the reactors restarted have been approved to operate beyond 40 years. These reactors include Takahama-1 (826 megawatts (MW)), Japan’s oldest reactor (50 years).

Still among the existing reactors, 3 reactors (4 GW) have been approved for restart by the Nuclear Regulation Authority (NRA) but have not restarted commercial operation yet: Kashiwazaki Kariwa-6 &-7 (1,356 megawatts each), and Tokai-2 (1,100 MW). The restart of these two Kashiwazaki Kariwa reactors is confronted with local public opposition, and work on safety measures is scheduled to be completed in August 2029 for unit-7 and in September 2031 for unit-6 due to the delay in the construction of anti-terrorism facilities announced on February 27, 2025. At Tokai-2, work on safety measures is scheduled to be completed in December 2026.

Another 8 existing reactors (8 GW) have applied for restart. Among this group of reactors, two need to overcome difficult obstacles: Shika-2 (1,206 MW) and Tsuruga-2 (1,160 MW). On January 1, 2024, the site of the Shika nuclear power plant was struck by the Noto Peninsula Earthquake. It will take several years to determine the impact of the seismic zone on the plant. On November 13, 2024, Tsuruga-2’s application was rejected by the NRA due to an active fault running beneath the reactor.

The last 8 existing reactors (8 GW) are inactive. They did not apply for restart after spending more than a decade on outage. The restart of these reactors is doubtful, particularly that of Kashiwazaki Kariwa-1 to -5 (1,100 MW each). At least one of these five reactors is required to be decommissioned if Kashiwazaki Kariwa-6 & -7 are restarted.  

Regarding the reactors under construction, Ohma (1,383 MW) and Shimane-3 (1,373 MW) applied for start and could be operational around FY 2030. And the construction of Tokyo Electric Power Company (TEPCO)’s Higashidori-1 is indefinitely suspended. It must also be noted that this reactor is not even defined as “under construction” by the International Atomic Energy Agency because the first major placing of concrete for the base mat of the reactor building has not been made (i.e., a prerequisite by global standards).

Four Scenarios to Appropriately Capture Uncertainty

Making projections for nuclear power in Japan is an arduous task owing to the various circumstances each reactor must deal with. 

To appropriately capture this uncertainty four scenarios are developed in this column: “Low”, “Medium”, “High”, and “Maximum”. All scenarios depict possible paths by using a broad range of assumptions (Table 1).

Table 1: Japan – Scenarios and Assumptions for Nuclear Power Projections

For the sake of conciseness, only the most important assumptions are presented below:

• Reactors restart dates; based on empirical observations from the 14 restarted nuclear reactors, it is possible for a reactor to be restarted three years after being approved for restart and six years after applying for restart. Therefore, reactors which have been approved for restart and those which have applied for restart are assumed to resume commercial operation on April 1, 2030 [Medium, High, and Maximum scenarios]. Inactive reactors are assumed to restart on April 1, 2040 [Maximum scenario].    
• Reactors start dates; Ohma and Shimane-3 could start commercial operation around FY 2030. Therefore, they are assumed to start commercial operation on April 1, 2030 [High and Maximum scenarios]. TEPCO’s Higashidori-1 is assumed to start on April 1, 2040 [Maximum scenario].   
• No new reactor other than those already under construction; it appears very unlikely that any projects advancing immature reactor designs characterized by a lack of construction experience and a limited operating track record (e.g., small modular reactors…) and without an identified site could be commissioned by FY 2040. Therefore, this option is not pursued in any scenario.  
• Reactor lifetime and lifetime extension; in Japan, nuclear reactors can obtain a beyond 40-year operating license allowing them to extend their lifetime by 20 years and the period during which they have been in long-term outage due to external factors. For example, a reactor affected by an earthquake resulting in a 10-year outage could be allowed to have a 70-year lifetime. As a reminder, no nuclear reactor has ever been operated for 60 years in the world. The ongoing record is 55 years, Beznau-1 (380 MW) in Switzerland. Therefore, scenarios assume both a strict limit of 60 years [Low and Medium] and 60 years + long-term outage period [High and Maximum].   
• Capacity factor; Between 2016 and 2023, the capacity factor of restarted nuclear reactors was 73.8% on average. Therefore, the capacity factors assumed across the different scenarios are 70% [Low], 75% [Medium], and 80% [High and Maximum].

Projections Warn of Nuclear Power Output Below Government Targets

The four different scenarios display distinct trajectories for nuclear power capacity in operation from FY 2024 to FY 2050 (Chart 2). The projections for the period FY 2041-FY 2050 are for reference purposes only, as the focus of this column is on FY 2030 and FY 2040 to compare with the Japanese government targets.

Chart 2: Japan – Nuclear Power Capacity in Operation, Projections FY 2024-FY 2050

In the Low scenario, nuclear power capacity in operation is projected to decrease from FY 2028 and become zero in FY 2045.

In the Medium scenario, nuclear power capacity in operation is projected to increase to 17 GW in FY 2030. Following a wave of closures in the FY 2030s due to reactors reaching the end of their lifetime, nuclear power capacity in operation is projected to decrease to 13 GW in FY 2040.

In the High scenario, nuclear power capacity in operation is projected to increase to 25 GW in FY 2030. Thanks to a more favorable lifetime extension assumption than in the Low and Medium scenarios, no reactor is closed until the end of FY 2045.

In the Maximum scenario, nuclear power capacity in operation is projected to increase to 28 GW in FY 2030 and 36 GW in FY 2040.

Then, the future shares for nuclear power are estimated using total electricity generation projections by the Japanese government: 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

Neither in the Medium scenario nor in the High scenario, the shares of nuclear power reach the government targets of 20-22% in FY 2030 and 20% in FY 2040.

The High scenario falls short of the FY 2030 target. The gap widens in FY 2040, with the projected nuclear power share being 4-5 percentage points less than the government target. This finding is striking given the optimistic assumptions underlying this scenario.

Only the Maximum scenario can deliver the government targets. In this scenario in FY 2040, all but one of the 33 existing reactors are in operation and all of them are allowed to operate beyond 60 years, 3 new reactors start operation, and all the 35 reactors operate at a high-capacity factor of 80%. The actual situation is far from this utopian description. Thus, one should recognize that the government goals are exaggeratedly complicated to achieve.

This conclusion is problematic because it means that it can already be predicted that Japan will suffer from a significant lack of decarbonized electricity, unless renewable energy (RE) exceeds government unambitious targets of 36-38% in FY 2030 and 40-50% in FY 2040.

Whereas nuclear power seems condemned to disappoint, RE can outperform. Nevertheless, fully unleashing Japan’s RE potential starts with the government changing its vision for the country’s future electricity mix.