Today, on the 15th anniversary of the Fukushima Daiichi nuclear disaster, Japan’s nuclear story is one of a widening gap between political ambition and physical reality – one that the country’s political leadership keeps pretending does not exist. On this anniversary, that gap deserves honest examination.

On February 18, 2025, the Japanese government adopted its Seventh Strategic Energy Plan, pledging that nuclear power would supply 20 percent of the country’s electricity by 2040. Before the disaster, Japan operated 54 nuclear reactors that collectively supplied roughly 30 percent of the country’s electricity. Today, after 15 years of declared commitment to nuclear revival, 15 reactors are in operation across a fleet of 33 that are technically operable. The share of Japan’s electricity generated from nuclear power reached 8.3 percent in 2024. The government’s target of 20 percent by 2040 is almost certainly out of reach. And Japan has been here before.

The implausibility of Japan’s nuclear targets became visible as early as 2016. At the time, it was becoming apparent that the new safety requirements published in July 2013 were driving up costs for safety refurbishments, rendering nuclear power plants an unviable business option for operators. In 2022, I returned to the same argument against the backdrop of Russia’s invasion of Ukraine, which briefly renewed public support for nuclear energy in Japan. The underlying structural obstacles – surging refurbishment costs, legal challenges, and a utilities sector unwilling to invest at the scale required – made a genuine revival impossible. The conclusion then was that Japan would retain nuclear power, but at a much lower level than official targets implied.

By 2026, the arithmetic has not improved. Instead, the Japanese government simply moved the target. Where Japan’s Sixth Strategic Energy Plan aimed at generating 20 to 22 percent of electricity from nuclear power by 2030, this target has now been pushed back by a decade. Both targets express political hopes rather than the reality of restart progress. 

The pattern across Japan’s fleet is one of decommissioning outweighing restarts. Of the 54 reactors Japan operated prior to the 2011 nuclear disaster, there are still 33 technically operable reactors, but only 15 are in operation and producing power. Three more have received restart approval but remain offline due to ongoing safety upgrades. Eight more have submitted applications, though several face unresolved obstacles – including Shika-2, which sits near the epicenter of the devastating Noto Peninsula earthquake of January 2024, and Tsuruga-2, where the Nuclear Regulation Authority concluded in July 2024 that the reactor could not meet safety standards due to an active fault beneath the site. Meanwhile, 22 reactors have entered the process of decommissioning since 2011.

Why is the pattern unlikely to change? Three structural factors have been consistent across every iteration of this analysis. 

First, safety upgrades are expensive and slow. When the new safety standards were introduced in 2013, utilities estimated total upgrade costs at 1 trillion yen. By 2015, that figure had more than doubled to 2.4 trillion yen. Costs have continued to rise, and the timeline for completing anti-terrorism facilities – a requirement added after the 2013 standards were issued – has pushed restart schedules deep into the late 2020s and early 2030s. 

Second, legal challenges remain a constant hazard. Court rulings blocking or delaying restarts have plagued operators, and even rulings that are eventually overturned on appeal create years of uncertainty that utilities must price into their investment calculations. 

Third, and most consequentially, Japan’s fleet is aging. The reactors approved for operation beyond 60 years are precisely those whose continued operation defies the logic of a revival: extending the life of aging plants is not the same as building new capacity.

The government knows this. The Seventh Strategic Energy Plan acknowledges explicitly that more than 3 gigawatts of existing capacity will reach the 60-year operational limit before 2040. And after that threshold, the fleet’s contribution will decrease significantly. New construction is theoretically possible, but no new reactor has broken ground since 2011. Construction timelines of 15 years or more mean that any reactor commissioned today would not produce electricity until the 2040s – after the target date itself. The government’s stated plan to “work on the development and deployment of next-generation advanced reactors” rests on the hope that a next generation of nuclear reactors will be developed in the near future. Given that this technology is not yet market-ready, it is unlikely to close the gap by 2040. 

None of this means nuclear power has no future in Japan. The 15 reactors currently operating are contributing meaningfully to the grid. The case for restarting additional approved reactors as quickly as safety permits is a reasonable one. Consider the most optimistic scenario of Japan restarting all 25 reactors that electricity utilities seek to put back on the grid. They amount to about half of the installed capacity available prior to the Fukushima accident and could provide close to 15 percent of Japan’s electricity demand. Even if safety refurbishing speeds up considerably, utilities overcome all legal challenges, and safety concerns surrounding Shika-2 and Tsuruga-2 are resolved, the resulting electricity generation capacity from nuclear power plants will fall short of the government target. 

What is more, at least three of the reactors currently in operation will meet the 60-year operational limit in the 2030s. According to my calculations, the best-case scenario Japan can currently hope for is to generate 15 percent of its electricity from nuclear power by 2030 and about 10 percent by 2040. A recent analysis by the Renewable Energy Institute came to similar conclusions, projecting a 19 percent share in 2030 and a 15 percent share in 2040 in their “high scenario.” Even this is a case for nuclear as a modest, declining contributor to Japan’s energy mix – not for the 20 percent target that the government continues to announce.

Japan has spent 15 years calling this a revival, but the numbers say otherwise. The consequences extend well beyond Japan’s grid. Nuclear power is pursued in the name of environmental friendliness and energy security. In fact, the nuclear power target is a key pillar of the climate mitigation strategy Japan has submitted as a signatory to the Paris Agreement. Missing it will translate into a failure to deliver on its greenhouse gas emission reduction targets, particularly as Japan has been filling the gap with energy produced from coal, gas, and oil rather than renewable energy. This trajectory risks tarnishing Japan’s international reputation in the context of global efforts to tackle climate change. 

It also leaves Japan dependent on coal and gas imports, thereby undermining its stated policy goal of greater energy self-sufficiency–a goal that appears ever more important in light of the current situation in the Middle East. Not addressing the nuclear power gap undermines the very policy goals the Japanese government seeks to achieve with a nuclear revival.