In 1993 SKB launched its Encapsulation Plant Project. Within this project, SKB has:
a) designed a facility for encapsulation of nuclear fuel
b) laid down the design premises for a canister for disposal of nuclear fuel
c) tested and developed fabrication methods for copper canisters
d) evaluated the long term chemical and mechanical behaviour of the canister
e) made preliminary plans for a factory for the production of copper canister
f) constructed a canister laboratory for full scale testing of the key operations in an encapsulation plant.
The conclusions of this project were that a canister consisting of an outer layer of 50 mm copper over an insert of cast nodular iron would provide sufficient corrosion protection and would have sufficient mechanical strength. This canister can be produced by several methods such as forming from rolled plates, hot extrusion, and pierce and draw. These methods have been tested at full scale and the results from these manufacturing tests will be presented and discussed. The canister will be sealed by electron beam welding in the encapsulation plant and the integrity of the weld will be verified by ultrasonic testing and high-energy radiography. The final development work in this area will be performed in the Canister Laboratory in Oskarshamn, Sweden. The laboratory is now in operation and is equipped with a 100 kW EB-welding unit, a 9 MV digital X-ray unit and a state-of-the-art phased array ultrasonic testing unit.