No country has yet built a final destination for its spent nuclear fuel. On the afternoon of August 26, 2026, Finland's Posiva began drilling the first disposal hole at the Onkalo permanent repository, more than 400 meters underground on Olkiluoto Island. In early August, Finland's Radiation and Nuclear Safety Authority (STUK) had already assessed that the safety requirements for an operating license were met, moving the project from the review-document stage to actually cutting into bedrock that is 1.9 billion years old. The hole being drilled must stay within 25mm of its centerline along its entire length. This exacting tolerance stems from a design that isolates radioactive material without relying on ongoing human oversight.
A 78-Ton Boring Machine and a 25mm Margin
The machine used is the Deposition Hole Boring Machine (DHBM), built by Germany's Herrenknecht AG and accepted by Posiva in June 2022. The main unit measures 9.13m long, 3.15m wide, and 3.93m tall, weighing 78 tons. It is paired with a 7m energy unit (22 tons) and a 4.1m-tall drilling process plant (18.5 tons). According to World Nuclear News, Posiva held a kickoff meeting on August 25, then spent the morning of the 26th making final equipment adjustments before starting on the bedrock that afternoon.
This was not a first attempt. At the end of 2022, a Herrenknecht crew drilled four test holes, and Posiva's own crew later drilled four more with supplier support. Construction and Operations Manager Kimmo Lehtola said, "We have already practiced with several holes, and preparations for the actual disposal hole drilling have been ongoing for a long time." He added, "The team has been looking forward to this day. It's wonderful to have the opportunity to drill, for the first time, a hole that will actually become part of the final disposal."
The finished hole will be 8.4m deep and 1.75m in diameter. Deviation from the centerline must stay within 25mm along the entire length; any hole exceeding this will be excluded from final disposal. If a hole bends, the fit of the canister and the surrounding bentonite buffer will not match the design. For this reason, Posiva has set up an inspection process for the first three holes, remeasuring after each drilling is completed.
Lehtola also gave a sense of pace. Under Finnish conditions, drilling one 8-meter hole takes roughly 10 working hours, with harder bedrock slowing the process further. Once full-scale production begins, the target is two holes per week. The first disposal tunnel currently being drilled is about 330 meters long and is planned to hold roughly 30 disposal holes; at two holes per week, filling a single tunnel would take about 15 weeks, or roughly four months.
What Copper and Bentonite Are Meant to Stop
The KBS-3 method used at Onkalo is a multi-barrier design developed in Sweden. Spent fuel is sealed inside copper canisters with cast-iron inserts. The cast iron bears the structural load, while the copper faces the groundwater and surrounding rock. Dividing roles between materials is the backbone of this method.
Inside the disposal hole, the canister is wrapped in a bentonite buffer. Bentonite is a clay that swells when it absorbs water, sealing the gap between the hole and the canister on its own and narrowing pathways for groundwater. The tunnels connecting the disposal holes are backfilled with the same type of swelling clay. Finally, the 1.9 billion-year-old Olkiluoto bedrock itself serves as the outermost barrier.
The reason for layering barriers is to account for the possibility that any single one might not perform as expected. Even if the copper is compromised, the bentonite slows the movement of groundwater; even if the clay degrades, the low permeability of the bedrock remains. Posiva explains that this layering prevents radioactive material from reaching the surface. The fact that it does not depend on continued human monitoring or repair is the decisive difference from above-ground interim storage.
The disposal site is often described as being 450 meters underground, but Posiva's own explanation is somewhat more precise. The deepest point the Onkalo facility reaches is about 450 meters, while the actual disposal tunnels where fuel is placed sit between 400 and 430 meters underground. The hole now being drilled is also located at a depth exceeding 400 meters. The plan calls for placing 6,500 tons of spent fuel (in uranium equivalent) here, distributed across roughly 3,250 canisters.
The overall scale has also been disclosed. World Nuclear News reported that over a 100-year operating period, roughly 100 disposal tunnels will be drilled, totaling about 35 kilometers. The maximum length per tunnel is 350 meters, and the roughly 330-meter tunnel currently being drilled is close to that upper limit.
Forsmark's Groundbreaking, Cigéo's Cost Estimate, and Yucca Mountain's Void
Sweden's Forsmark repository, which also uses the KBS-3 method, broke ground in January 2025. According to an announcement by Vattenfall, the plan calls for about 6,000 canisters holding up to 12,000 tons of spent fuel at a depth of roughly 500 meters, with operations expected to begin in the 2030s and all tunnels completed by the 2080s. No figure has been given for the repository alone; the operator, SKB (Swedish Nuclear Fuel and Waste Management Company), cites a combined investment of SEK 21 billion covering the repository, the encapsulation facility, and the expansion of the existing low- and intermediate-level waste repository (SFR). Converted at the SEK-to-JPY rate of 16.74 yen on August 27, 2026, this comes to approximately 351.5 billion yen. In terms of canister count, this is about 1.8 times Onkalo's roughly 3,250 canisters, but construction began nine years later.
France's Cigéo is at the same "final stage of regulatory procedure" as Onkalo. The application for a construction license (DAC) was filed in January 2023, the technical review by the Nuclear Safety and Radiation Protection Authority (ASNR) was completed in November 2025, and the mandatory public consultation also concluded over a 60-day period from May 18 to July 16, 2026. What follows is the publication of the investigative commission's conclusions and review of the draft decree, before the government issues the final decree—a structure paralleling Onkalo's wait for a government licensing decision. The schedule indicates that excavation of underground access tunnels will begin around 2035, excavation of storage chambers for nuclear surface facilities and intermediate-level long-lived waste around 2040, and storage chambers for high-level waste around 2045, with limited partial operation (the pilot phase) estimated by ASNR documents to begin sometime between 2045 and 2050.
Regarding project costs, NucNet reports the latest overall estimate at approximately €33.4 billion before tax and approximately €37.0 billion including tax. Converted at the euro-to-yen rate of 185.57 yen on August 28, 2026, these amount to approximately 6.2 trillion yen and 6.9 trillion yen, respectively. Because the scope and currency differ from Forsmark's investment figure, these amounts cannot be directly compared to draw conclusions about relative merit.
The United States has moved in the opposite direction. After decades of study costing billions of dollars, the Yucca Mountain project saw the DOE attempt to withdraw its license application in 2010, but the NRC's (U.S. Nuclear Regulatory Commission) review panel rejected this in June of that year. The technical and environmental review itself resumed in 2013, with a safety evaluation report completed in 2015 and a supplement to the environmental impact statement in 2016. However, the court-style adjudicatory hearing process needed to move forward has remained suspended since September 2011 and has not resumed to this day, leaving the matter in legal limbo. Meanwhile, spent fuel has continued to accumulate, with approximately 95,000 tons now held in interim storage across 73 nuclear plant sites nationwide, growing at a rate of roughly 2,000 tons per year. The inability to decide on a disposal site has simply remained a burden carried by each individual site.
| Facility | Current Stage | Target Operational Timeline |
|---|---|---|
| Onkalo (Finland) | Disposal hole drilling begun (August 2026) | Awaiting government licensing decision |
| Forsmark (Sweden) | Construction begun (January 2025) | 2030s |
| Cigéo (France) | Technical review and consultation complete, awaiting decree | Pilot operation expected around 2045–2050 |
| Yucca Mountain (USA) | Review suspended since September 2011 | Undetermined |
Looking at these four cases together, it becomes clear that deep geological disposal as a method is not itself at an impasse. What has stalled is the American project, over an unresolved decision about location.
"End of 2026" Is Posiva's Goal, Not a Government Decision
Posiva President and CEO Ilkka Poikolainen said, "Our ambitious goal is to have operational readiness for the start of final disposal by the end of 2026." The word "ambitious" is not modesty. The company applied for an operating license for the spent fuel encapsulation plant and final disposal facility on December 30, 2021, requesting a license period from March 2024 through the end of 2070. The start date envisioned at the time of application has already slipped by more than two years.
Regulatory judgment advanced a step in early August. STUK concluded that the facility met the safety requirements for an operating license—the first such assessment in the world for a spent nuclear fuel final disposal facility. The Ministry of Economic Affairs and Employment indicated it could prepare a draft licensing decision for the government as early as autumn, but did not specify when the government would actually vote on it.
The path to this point has been long. The Eurajoki site was selected in 2000, Parliament approved the underlying decision-in-principle in 2001, the construction license was applied for in December 2012 and obtained in November 2015, and construction began in 2016. Posiva is a joint venture between the power utility Fortum and industrial power company TVO (Teollisuuden Voima Oyj), and the two companies have built, on their own, a destination for the spent fuel they generate.
Some figures are absent from this announcement. Posiva has not disclosed the drilling cost per disposal hole, the latest overall project cost, or how many out-of-tolerance holes the plan can absorb. Knowing how many rejected holes can be tolerated against the roughly 30-hole-per-tunnel plan would make it possible to gauge how realistic the two-holes-per-week target actually is.
Finland Reached Drilling in 26 Years; Japan Remains Stuck at the Literature Survey
Japan's high-level radioactive waste disposal effort is still at the stage of searching for a location. The Nuclear Waste Management Organization of Japan (NUMO) began literature surveys in the towns of Suttsu and Kamoenai in Hokkaido in 2020—the first of a three-stage site selection process consisting of a literature survey, a preliminary survey, and a detailed survey. As of August 2026, no municipality has advanced to the next stage, the preliminary survey.
Finland selected Eurajoki in 2000 and reached the point of drilling disposal holes 26 years later. Japan has yet to reach that starting point—site selection itself. If a disposal site were decided today and the same 26 years were required, the first disposal hole would not be drilled until the 2050s. That said, Onkalo secured an early political settlement through Parliament's decision-in-principle in 2001; without that approval, the process would not have proceeded on the same timeline.
While a location remains undecided, fuel continues to sit where it was generated. The roughly 95,000 tons scattered across 73 sites in the United States, growing year by year, is the consequence of exactly this. Japan's spent fuel, too, continues to be managed at nuclear plant sites and reprocessing facilities, separate from any resolution of the disposal-site debate.
Onkalo has three milestones still ahead: the government's operating license decision, the production of the first canister at the encapsulation plant, and the first actual placement of a canister in a disposal hole. Once these three are achieved, deep geological disposal will shift from being a subject of blueprints and review documents to a technology that can be discussed in terms of operating record. When Japan eventually debates where to site its own repository, the comparison it faces will no longer be another country's plans on paper, but a facility that is actually running.