Spent fuel (SF) from the Swiss nuclear power plants and vitrified fission product solutions from reprocessing will be disposed of in the high-level waste (HLW) repository. The repository will also have tunnels for long-lived intermediate-level waste (ILW). The repository will be required from around 2050.
A ramp or a vertical shaft will provide access to the waste emplacement zone at a depth between 400 and 900 metres. The pilot facility can also be used to check the behaviour of the safety barriers during a monitoring phase after the disposal tunnels in the main facility have been closed.
Main facility SF/HLW
The high-level waste repository comprises disposal tunnels with a diameter of 2.5 metres for the emplacement of containers with spent fuel and vitrified high-level waste.
The functioning of the repository will be monitored in the pilot facility using a representative component of the waste.
Investigations relating to the construction and operation of the repository are carried out in the test area with a rock laboratory.
All disposal zones are located at a depth of around 600 metres. Access is via a tunnel and a shaft.
The locomotive drives through the access tunnel to the underground disposal tunnels.
In the disposal tunnel, the container is loaded onto a support of clay blocks on an emplacement trolley and brought to the emplacement position.
Once in position, the container resting on the clay blocks is deposited in the tunnel and the trolley is pulled back.
The containers are placed individually one after another in the tunnel with spaces in between.
The tunnel is continuously backfilled with compacted bentonite granulate.
Once the emplacement phase is complete, the open accesses to the disposal tunnels are backfilled and sealed.
When the decision is made to finally close the entire facility, open tunnels and the shaft will be backfilled and sealed.
The disposal containers can be retrieved at any time.
In a deep geological repository, safe long-term containment of the waste is provided by a system consisting of three engineered barriers and one geological barrier.
In the case of spent fuel, the cladding containing the uranium pellets represents the first engineered barrier. Packaged in thick-walled metal containers (second engineered barrier), the fuel elements are placed on a bentonite plinth in the disposal tunnel and the entire tunnel is backfilled with bentonite granulate (third engineered barrier). Together with the overlying formations, the host rock forms the geological barrier.
High-level fission product solutions from reprocessing are immobilised in a glass matrix that corrodes extremely slowly. The metal containers and the bentonite backfill again represent the other two engineered barriers.
Safety barriers in a repository for high-level waste.
Glas matrix, containing radioactive material
Backfill with bentonite