Japan has resumed operations at the world's largest nuclear power plant to address soaring electricity demands amid a global oil crisis. However, the restart underscores a critical issue: the country is rapidly running out of space for spent nuclear fuel and lacks a viable permanent disposal strategy for radioactive waste.
Kashiwazaki-Kariwa Restart and Storage Concerns
The restart of the No. 6 reactor at the Kashiwazaki-Kariwa Nuclear Power Station earlier this year was intended to revive the nuclear industry. Yet, according to the Federation of Electric Power Companies of Japan, this plant is among three whose cooling pools will reach full capacity within five years. Takeyuki Inagaki, general manager of Kashiwazaki-Kariwa, warned, "Without solid fuel management plans, our power generation will stall sooner or later."
After decades of searching for a permanent storage site for highly radioactive spent fuel, the government is now considering Minamitorishima, a remote Pacific island south of Tokyo. This proposal has faced skepticism and criticism due to Japan's historically arbitrary actions regarding spent fuel and radioactive waste management.
Since the March 2011 Fukushima disaster—triggered by a 9.0 earthquake and tsunami that caused meltdowns at three TEPCO reactors—only 15 of Japan's 54 reactors have restarted. The disaster displaced approximately 160,000 people, and some areas remain uninhabitable.
Kashiwazaki-Kariwa, also operated by TEPCO, was shut down after Fukushima as part of a nationwide nuclear halt. The spent fuel pool at the No. 6 reactor, now 88% full, is visible from an observation area. TEPCO has installed filtered venting systems and hydrogen explosion prevention devices as additional safety measures based on lessons learned from Fukushima.
Prime Minister Sanae Takaichi is pushing to bring more nuclear plants online, which will generate even more spent fuel. Without a permanent storage plan, reactors may have to close when storage space runs out.
Fuel Recycling Plan Stalled
Two options exist for dealing with spent nuclear fuel: direct disposal as waste or recycling to extract plutonium and uranium for reuse. Japan insists on recycling, arguing it supports the resource-poor nation's energy needs while reducing waste toxicity and volume. However, a reactor designed for plutonium reuse, a key part of the recycling plan, has failed. Reprocessing cannot handle all the spent fuel, adding to a plutonium stockpile already sufficient to arm thousands of atomic bombs. Experts suggest Japan should also consider direct disposal.
As of December 2025, cooling pools at 17 Japanese nuclear plants held over 17,000 tons (15,422 metric tons) of spent fuel, using nearly 80% of total storage capacity, according to the Ministry of Economy, Trade and Industry. Lila Okamura, a Senshu University professor and expert on environmental politics and nuclear waste management, noted that Japan also must deal with "massive and largely unknown high-level nuclear waste from the Fukushima disaster."
Choosing a final disposal site and building a facility would require 100 years, with tens of thousands of years of monitoring deep underground. Okamura stressed that for such a generations-long project, Japan should plan carefully and not rush the current uncertain plan.
Remote Island Considered
Weeks after the No. 6 reactor at Kashiwazaki-Kariwa restarted for the first time in 14 years, Industry Minister Ryosei Akazawa approached Ogasawara village to request a feasibility study for a high-level radioactive waste site on Minamitorishima, an island administered by Ogasawara, part of Tokyo. Akazawa stated, "With a lot of spent fuel accumulating at nuclear power plants across the country, a final disposal of radioactive waste is a crucial challenge that must be resolved."
Minamitorishima, about 2,000 km south of Tokyo, has no permanent residents. The Japanese army is building a firing range for long-range surface-to-ship missiles as a deterrent to China, and the island also has deep-sea deposits rich in rare earth minerals. Satoshi Takano, a member of a government panel on final disposal, said, "The move seems political. There will be little opposition from a government-owned remote island."
Some experts note that Minamitorishima sits on a geologically stable tectonic plate, making it potentially suitable. However, many residents of Ogasawara and two nearby islands have raised safety and tourism concerns. Ogasawara assembly member Yusuke Hirano commented, "I was baffled when I heard about the plan. I think nuclear waste is incompatible with islands that are a UNESCO Natural World Heritage site."
Struggle to Find Final Disposal Site
Finding a community willing to host a highly radioactive dump site has been difficult despite financial incentives. Minamitorishima is the fourth location to undergo a feasibility study since the government began searching in the early 2000s. The entire review process will take about two decades. Municipalities participating in the first stage can receive up to 2 billion yen (USD 12.8 million) in subsidies, with the next stage offering up to 7 billion yen (USD 44.7 million). Funding for a final study has not been disclosed.
The world's first final disposal site for spent nuclear fuel is set to open in Finland later this year. Britain, Germany, and the United States have abandoned reprocessing largely due to high costs and technical challenges, while several other countries are discussing direct disposal plans.
Inagaki stated that TEPCO is transferring spent fuel from the No. 6 reactor to other reactors at the plant with more space, but the utility hopes to resume shipments to a dry cask storage facility in northern Japan as a near-term solution. Other utilities with nearly full pools have announced plans to build dry-cask storage at their plants.
Many residents worry about Japan's growing stockpile, as high-density storage of spent fuel could increase overheating risks. Mie Kuwabara, a civil activist in Niigata, questioned, "Where will it go next?" She added, "It's irresponsible to accelerate restarts and produce more spent fuel without deciding its final destination." Kuwabara is also skeptical about using Minamitorishima, saying, "It's like saying that it's OK to put a facility there because nobody is around to complain if there is a problem. It's scary."
