Excavation has begun of final disposal tunnels at the Onkalo deep geologic repository for spent nuclear fuel at Olkiluoto in Eurajoki municipality, southwest Finland.

Posiva Oy, the company responsible for the final disposal of spent nuclear fuel from Finland’s fleet of four commercial nuclear reactors, said the start of excavation is a significant milestone, coming after years of research and development at the site. It means Posiva is likely to become the first operator to start deep geological final disposal of spent nuclear fuel.

The encapsulation of spent nuclear fuel and the placement of canisters containing the fuel in tunnels will start once the Finnish government grants an operating licence for the facility. Posiva said final disposal is likely to start in the mid-2020s.