The Onkalo nuclear waste repository in western Finland received the world’s first operating licence for the permanent disposal of spent nuclear fuel on 22 October 2026. The decision follows more than 40 years of research, political decisions and construction. But it does not mean disposal has begun: operator Posiva must finish commissioning and pass a final regulatory inspection before radioactive fuel can be placed underground.
Located at Olkiluoto, in the municipality of Eurajoki, the repository extends more than 400 metres below the surface. The Finnish government’s licence covers spent fuel from the Olkiluoto and Loviisa nuclear power plants. Finland has thus reached a milestone in a problem faced by every country that uses nuclear energy: what to do with spent fuel long after it leaves a reactor.
Planning for nuclear waste began in the 1980s
Finland did not arrive at Onkalo through a single decision. In 1983, the government approved a plan to investigate permanent disposal in Finnish bedrock and established a timetable for finding a site. Researchers examined geological data from more than a hundred possible locations, then narrowed the options through successive field studies.
By the 1990s, investigations focused on several candidates, including areas near existing nuclear power plants. TVO and Fortum established Posiva in 1995 to manage final disposal of their spent nuclear fuel. The company selected Olkiluoto in 1999, after studies of geology, infrastructure and the effects on nearby communities. An existing nuclear site was a practical advantage, but it still had to satisfy safety and political requirements. Posiva’s history of the site investigations sets out the process.
The Finnish government approved the project in principle in December 2000, and Parliament endorsed it in May 2001. Construction of an underground research facility started in 2004. The government then granted a construction licence in 2015 for the repository and its surface encapsulation plant. Only after further construction, tests and regulatory assessments came the operating licence of October 2026.
Why the local community accepted the site
A crucial feature of the Finnish procedure was that the prospective host municipality had a legal right to veto the project. The municipal council of Eurajoki chose not to use it. In January 2000, councillors voted 20 to seven in favour of hosting the repository.
Eurajoki had lived alongside nuclear power for decades. Jobs, tax revenue and familiarity with power plants helped shape local attitudes. Environmental impact assessments and public consultations also formed part of the decision-making process. Yet the council vote demonstrates that acceptance was not unanimous.
Academic research on the Finnish repository identifies trust in institutions and existing economic relationships as important parts of the story. Other research on public dialogue points to limits in how residents could influence decisions, including unequal power between institutions and citizens. Onkalo is therefore not simply an example of universal local enthusiasm. It shows how a formal local veto, prolonged consultation and an established nuclear industry helped make a contested choice politically possible.
How the Onkalo nuclear waste repository is designed to work
Onkalo uses deep geological disposal, based on a method developed in Sweden. Instead of requiring active surface management forever, the plan is to isolate spent nuclear fuel through several different protective layers.
After a period of cooling and interim storage, fuel assemblies will be placed in canisters with a cast-iron insert and a corrosion-resistant copper outer shell. The sealed canisters will be lowered into deposition holes around 430 metres underground. Bentonite clay will surround them. When it absorbs water, the clay swells, forming a buffer. The stable bedrock adds a natural barrier, while tunnels are eventually to be filled and sealed.
The principle is multiple complementary barriers, rather than reliance on one container or one geological feature. Their long-term performance must be assessed using experiments, geological evidence and models over timescales far beyond a human lifetime. That leaves uncertainty and its careful assessment central to the safety case.
Posiva has tested equipment and procedures without using radioactive spent fuel. It began a trial of the disposal process in August 2024. By March 2025, the company reported that five test canisters had been encapsulated and transferred underground, with one retrieved in a separate test. These preparations are not the same as permanent disposal of actual spent nuclear fuel.
An operating licence does not mean disposal can start
The independent regulator is Finland’s Radiation and Nuclear Safety Authority (Säteilyturvakeskus, STUK). On 4 August 2026, STUK issued a positive safety assessment, finding that the legal requirements for granting the licence had been met. The government used that assessment as the basis for its October decision.
The licence runs until the end of 2070 and allows Posiva to handle and dispose of up to 6,500 tonnes of uranium in spent fuel, equivalent to approximately 3,300 disposal canisters. Once operations are established, the plan is for no more than about 60 canisters to be disposed of each year. The disposal programme is expected to run for around a century, potentially into the 2120s, requiring further decisions beyond the present licence period.
Before operations begin, STUK must conduct a final inspection required under Finland’s Nuclear Energy Act. The authority can require corrective action and additional safety measures. The licence also requires updated periodic safety assessments and long-term safety documentation within ten years. Posiva has not provided an exact start date for disposal.
Who will remain responsible after Onkalo closes?
Finland has also established a framework for financing the work. Nuclear operators are required to cover the costs of managing their waste, with resources set aside in a state nuclear waste management fund. After the repository is closed, responsibility for the spent fuel will transfer to the Finnish state under national law. Information about the repository must be preserved for the authorities that will outlast the operating company.
The political and scientific debate over nuclear waste does not disappear with a licence. Long-term safety cannot be observed over the entire period for which isolation is intended; it must be assessed with evidence, experiments and modelling. Nor is Onkalo automatically a disposal solution for every future Finnish reactor or for other countries’ waste.
What Finland has achieved is substantial but specific: after decades of geological investigations, local and national decisions, construction and independent review, it has licensed a permanent repository for its existing nuclear power programme. Whether spent fuel can actually begin going underground now depends on the remaining safety checks, not another political announcement.
