To provide safer and more permanent storage, Posiva proposes to bury electrically-welded iron-and-copper capsules 400 meters underground. The capsules would be surrounded by clay barriers and capped with rubble and cement. The facility, which would have a 6,500 metric ton capacity, could likely hold Finland and Sweden's projected future nuclear waste. But that capacity doesn’t come close to the volume required by larger nations such as the United States, which has over 70,000 metric tons of waste piled up, and produces an additional 2,200 tons a year.
Though tunneling has been going on for over a decade, Posiva had to wait for the Finnish government to approve its 2012 construction permit application before it could begin the trickier task of loading radioactive waste into its metal coffins. That task may begin as soon as 2023, continue for up to a century, and end when operators fill in the access tunnels with rubble and cap them off with cement. Posiva estimates that installation and operating costs for the first century will be around €3 billion (US $3.21 billion).