The encapsulation and final disposal facility of spent nuclear fuel

In 2015, Posiva Oy received permission to build a used fuel encapsulation and disposal facility in Olkiluoto. Posiva started the construction of the disposal facility at the end of 2016 and the construction of the encapsulation facility in the summer of 2019. Posiva submitted an application for an operating permit to the Government at the end of 2021. The processing of the operating permit application material and the preparation of the safety assessment are ongoing at STUK.

The final disposal facility means the entity, which includes facilities for the final disposal of waste packages (repository) and related underground and above-ground auxiliary facilities. The encapsulation facility (above-ground) and disposal facility (underground) are connected to each other with an elevator shaft and canister transfer shaft as well as a separate access tunnel. In the above-ground encapsulation facility, the spent nuclear fuel is received, dried and packed into final disposal canisters. Before, spent nuclear fuel has been stored in water basins located at the sites of nuclear facilities in interim storages for spent nuclear fuel for 30–50 years.

The final disposal facility consists of an access tunnel that reaches a depth of approximately 450 metres, technical facilities located at a depth of 437 metres and central and final disposal tunnels to be built in phases during the facility’s use.  The final disposal system is composed of a tightly sealed iron-copper canister, a bentonite buffer enclosing the canister, a tunnel backfilling material made of Friedland clay, the seal structures of the tunnels and premises and the enclosing rock.