Onkalo, Finland’s deep geologic repository for spent nuclear fuel, has been characterized as a game changer for the long-term sustainability of nuclear energy by Rafael Mariano Grossi, director general of the International Atomic Energy Agency.
“Finland has had the determination to move forward with the project and to bring it to fruition,” Grossi said during a November 26 visit to Olkiluoto, Finland, where the repository is under construction. “Waste management has always been at the center of many debates about nuclear energy and the sustainability of nuclear activity around the world. Everybody knew of the idea of a geological repository for high-level radioactive nuclear waste, but Finland did it.”
Posiva Oy, the Finnish company tasked with researching and creating a method for the permanent disposal of spent fuel from Finland’s Olkiluoto and Loviisa nuclear power plants, obtained a license to construct the Onkalo repository in 2015, marking the first time that a construction license for a geological disposal facility was issued anywhere in the world. The site near the Olkiluoto plant was chosen following several years of screening a number of potential sites.
KBS-3 concept: The Onkalo repository is based on the KBS-3 disposal concept that was developed by the Swedish Nuclear Fuel and Waste Management Company in cooperation with Posiva. At the heart of the concept is the use of sealed copper canisters to encapsulate the spent fuel. After being placed in Onkalo’s system of tunnels, about 450 meters below ground level, the canisters will be embedded in bentonite clay, which will act as a buffer and protect the canisters from corrosion and minor movements in the bedrock.
The final tunnels: In July, Posiva announced the beginning of a two-year project to excavate Onkalo’s final disposal tunnels. According to the company, the work project will see the continuation of the excavation of the repository’s central tunnels, as well as the construction of the first five deposition tunnels. About 10 kilometers of tunnel space has been excavated in Onkalo to date, and it is estimated that another 40 km of tunnels will be excavated for the implementation of final disposal, which is planned to begin in 2024.