Development of Release Barriers
Technical R&D efforts focus on the release barriers used in final disposal. The technical release barriers – the copper canisters, the bentonite clay in which the canisters are enclosed as well as the back-filling material of the tunnels – play an essential role in safe final disposal.
The research and development efforts focusing on the release barriers are to a
great extent carried out in cooperation with the Swedish nuclear fuel management
company SKB (Svensk Kärnbränslehantering Ab). The techniques studied for the
fabrication of the external copper canister include broaching, deep drawing,
extrusion and forging. Electron beam welding and friction stir welding are
tested as possible methods for sealing the canister. Various non-destructive
methods are developed for the inspection of the canisters.
Apart from the canisters, technical R&D efforts encompass also the
bentonite used as buffer material in the deposition holes as well as the clay
used as back-filling material in the tunnels. For bentonite, it is important to
study the impact of heat, water and mechanical stresses on the material. The
manufacture and installation of the bentonite blocks used to back-fill the
deposition holes are also important development areas.