Spent nuclear fuel is packed in canisters in the aboveground encapsulation plant. Facilities for auxiliary operations are also located above ground.
Fuel is delivered to the receiving area of the encapsulating plant packed in transportation cask. This receiving area is also place where the empty final disposal canisters are delivered. In the encapsulation plant, both the transportation cask and the final disposal canister are then docked tightly inside the fuel handling cell, where the fuel is transferred from the transportation cask first to the drying station and then to the final disposal canister. When all fuel assemblies have been transferred to the canister, it is filled with argon gas and then tightly closed with an inner steel cover.
From the handling cell, the filled canister is transferred to a welding station. Now the canister lid is sealed with electron beam welding, which guarantees a tight and strong seam. Next, the tightness of the weld is inspected at a inspection station using non-destructive testing methods, such as x-ray and ultrasonic testing.
The encapsulation plant has been designed in such a manner that no hazardous amounts of radioactive substances will be released to the environment even if a disturbance occurs during the fuel encapsulation process. Canisters that have passed the inspection are then transferred either by lift or by the access tunnel with a special-purpose vehicle to the final disposal facility.
Facilities for Auxiliary Operations
In addition to the encapsulation plant, the aboveground buildings include facilities for auxiliary and supporting operations, such as the operational building, the ventilation building, the research building, storage hall and repair shop facilities as well as facilities required by the HVAC and electricity systems. Separate areas will be reserved for storing excavated materials and crushed rock as well as for the necessary construction site activities. The aboveground construction area of the disposal facility (i.e., the surface area of buildings, roads, storehouses and fields) is a total of approximately 20 hectares.
Figure: Longitudinal section of the encapsulation plant where different functions are:
- Receiving and storage area for new canisters
- Hot cell
- Copper lid welding chamber
- Weld inspection
- Canister surface cleaning area
- Canister lift for transfer of canisters into repository.