Onkalossa

Onkalossa is a proposed underground repository for spent nuclear fuel located in Eurajoki, Finland. Its primary purpose is to provide a secure, long-term solution for the final disposal of high-level radioactive waste generated from Finland's nuclear power plants. The repository is being constructed adjacent to the existing Olkiluoto Nuclear Power Plant.

The design of Onkalossa is based on the concept of KBS-3, which involves encasing spent nuclear fuel in copper canisters and then burying them deep within the bedrock. The repository will be located at a depth of approximately 400-500 meters, where the stable geological conditions are expected to provide natural isolation and containment for hundreds of thousands of years. The surrounding bedrock is primarily crystalline rock, which is considered suitable for this type of long-term storage.

Construction of Onkalossa began in 2004, and the facility is expected to be operational by the mid-2020s. The operation phase will involve transporting the spent fuel from the power plants, packaging it, and then lowering it into the disposal tunnels. Once filled, the tunnels will be backfilled and sealed. The project is managed by Posiva Oy, a company owned by the Finnish nuclear power producers. Onkalossa represents one of the most advanced deep geological repository projects globally, aiming to address the challenge of nuclear waste management in a safe and sustainable manner.