No country had ever reached this point. On Thursday the Finnish government handed the waste company Posiva an operating licence for Onkalo, its underground store for used reactor fuel at Olkiluoto on the west coast. It is the first time anywhere that such a permanent disposal site has been cleared to run.
The concept is simple to describe and hard to build. Spent fuel will be sealed inside copper canisters at a plant on the surface, then carried down a tunnel some 430 metres into ancient bedrock. Each canister goes into its own hole, packed around with bentonite clay that swells when wet. The rock and the clay are meant to keep the radioactivity isolated for an almost unimaginable stretch of time.
Under the permit, which runs until the end of 2070, Posiva may handle up to 6,500 tonnes of uranium produced at the Olkiluoto and Loviisa plants, roughly 3,300 canisters. Once fully up to speed it plans to emplace at most 60 a year, with disposal expected to continue into the 2120s. After that the tunnels will be backfilled and sealed, and the state takes over responsibility.
The licence does not mean fuel goes underground tomorrow. Posiva still has to finish commissioning, and Finland’s nuclear regulator STUK must carry out its own inspection before any operation can start. The company has declined to give a date. Within a decade it must also hand the regulator an updated long-term safety justification.
Chief executive Ilkka Poikolainen hailed a historic moment for a project more than four decades in the making. Other nations still searching for a site will be studying how the Finnish model performs in practice.
