Finland to open the world’s first final repository for spent nuclear fuel

Finland has positioned itself as first mover in the establishment of a spent nuclear fuel repository about 430 metres into the country's bedrock. The repository is expected to receive its first spent nuclear fuel in the middle of the 2020s, after obtaining a license for operation.

By Vattenfall Media Relations

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The handling of spent nuclear fuel has been a source of debate since the first commercial exploitation of nuclear energy in the second half of the twentieth century. On the one hand, nuclear fuel is a large source of fossil-free energy. It does, however, come at its price, as spent nuclear fuel is highly radioactive. In 2022, the European Union included nuclear energy into its EU taxonomy for sustainable activities after rigorous debates, thereby promoting investment into its production. As nuclear power will remain part of the European energy mix, member states are looking into final disposal options.

The global frontrunner in the push for a final solution to the increasing volumes of spent nuclear fuel is found in Finland, where Posiva has been tasked with the responsibility of building and operating Finland's final repository. Posiva has constructed such a facility and is in the process of obtaining a license to operate it. Finland will thus be the first country in the world to provide a repository in which nuclear waste can be safely stored for at least 100,000 years. Direct radiation will approximately decay already within 1,000 years. Afterwards, the spent nuclear fuel would still be damaging to the body upon ingestion, which is why it will remain inside the repository.

Final repository on Olkiluoto Island

Decades-long research into geological conditions led to the confirmation of Olkiluoto Island as the site best suited for Finland's final repository. There are two generally accepted final disposal options, namely near-surface disposal as well as deep geological disposal. In 2000, the Finnish government concluded in a decision-in-principle that the latter option was preferrable, and Posiva was asked to provide an in-depth study of the Olkiluoto bedrock.

Pasi Tuohimaa, spokesperson at Posiva, explains:

"In order to reach the depth of the future repository at about 430 metres, Posiva decided to construct the ONKALO facility, a combination of shafts and an access tunnel, in 2004. The bedrock condition was found to be suitable, so ONKALO was confirmed as the site for the repository. The construction license was granted by the Finnish government in 2015. ONKALO will continue to expand. Its tunnels will eventually reach a length of around 50 km."

Posiva determined the exact location of the repository by drilling holes into the crystalline bedrock and taking groundwater samples. The repository will be located where cracking of the bedrock and groundwater movement are minimal. Rigorous testing ensures long-term functionality, even in the case of extreme events such as earthquakes or coming ice ages. In Finland, 6,500 tons of spent nuclear fuel will be placed into approximately 3,250 canisters. It is the multi-barrier principle described below that will ensure the containment of radiation inside the repository to offer maximum protection for human beings and the environment.

SKB and the Swedish KBS-3 method

Posiva's counterpart in Sweden, the Swedish Nuclear Fuel and Waste Management Company (SKB), is currently working on the world's second final repository. It will be located close to Vattenfall's Forsmark nuclear power plant in the municipality of Östhammar, north of Stockholm. The two companies have long been collaborating on final disposal solutions, also due to the fact that bedrock conditions are similar in both countries. Posiva and SKB will both use what the latter calls the KBS-3 method, according to which several protective layers contain the spent fuel's radiation.

"In Sweden, approximately 12,000 tons of spent nuclear fuel will be stored in 6,000 copper canisters. The canister is the first barrier. The cast iron insert ensures stability, and the copper case prevents corrosion. The second barrier is bentonite clay. It will be placed around the canisters, so it can absorb surrounding water and expand. The clay will keep the canisters in place and protect them from movements in the bedrock. It will also keep the water away from them. The third and final barrier is the bedrock itself. The canisters will be placed safely at a depth of about 500 metres below ground," says SKB spokesperson, Jenny Rees. The Swedish final repository is expected to start operating in the mid-2030s after all necessary licenses have been obtained.