In the future, Switzerland will safely dispose of its radioactive waste in a deep geological repository over a very long time period. The surface infrastructure of a repository is composed of a surface facility and auxiliary access facilities as well as site development infrastructure and landfills for the materials arising from the excavation process. These will be needed for the construction, operation and closure of the repository. The waste itself will be emplaced in deep underground caverns and drifts.
Surface facility: gateway to the deep geological repository
All solidified waste is delivered to the surface facility from the interim storage facility. Low- and intermediate-level waste is packaged in drums that are already suitable for disposal. Before these are emplaced underground, they are enclosed in concrete containers, and any remaining voids are filled with cement. Vitrified high-level waste and spent fuel assemblies are transferred from transport and storage casks to disposal canisters which are then welded shut and examined. These work steps take place in the encapsulation plant for spent fuel assemblies. The waste is then transported to the underground facilities through the main access.
What belongs to a surface facility?
Elements of the surface facility
- Treatment facility for transport casks
- Fire station
- Processing plant for backfill and sealing materials
- Treatment facilities for waste water and operational waste
- Encapsulation plant for low- and intermediate-level waste
- Encapsulation plant for spent fuel assemblies and high-level waste
- Visitor centre
- Shaft hall
- Shaft tower
- Ventilation facility
- Power supply facilities
Other buildings are also needed to ensure the smooth operation of a repository: workshops, a fire station, security installations, a ventilation facility, an administration area, and a visitor centre. It also includes a processing plant for the backfill material that is used to seal and close the repository drifts and caverns. The entire surface facility of a combined repository requires an area of around six to eight hectares, and the tallest buildings will have a height of around 25 to 30 metres.
Encapsulation plant at the Zwilag interim storage facility in Würenlingen?
The encapsulation plant for spent fuel assemblies and high-level waste does not necessarily have to be located at the entrance to the repository; it could also be constructed at the site of the Zwilag interim storage facility.
- Fact sheet on an encapsulation plant outside the siting region (in German)
- Nagra work report NAB 20-14:“Verpackungsanlage hochaktiver Abfälle: Vor- und Nachteile verschiedener Standortvarianten” (in German)
- Joint statement of the regional representatives on the topic of siting an encapsulation plant for spent fuel assemblies (media release (in German) of the SFOE)
Auxiliary access facilities: connection to the underground
Aside from the surface facility, that also serves as the main access, auxiliary accesses are required. Auxiliary access facilities include all surface facilities that are needed for the operation and ventilation of the deep geological repository. They represent the surface interface to the repository for the supply or disposal of e.g. ventilation, power and water as well as for the transport of staff and materials. At three hectares, the auxiliary access facility, with its operations and ventilation shaft heads, is the largest structure. The operations shaft head is around 30 metres tall and the ventilation shaft head around 10 metres tall. The auxiliary access facilities for operations and ventilation can also be located in two separate auxiliary access facilities.
Aside from the surface facility and the auxiliary access facilities, additional temporary areas are needed for construction of site installations and landfills for the rock materials from excavation.
Where to locate the surface infrastructure?
Underground rock formations determine where the emplacement rooms will be constructed. It makes sense to keep the surface infrastructure close to the deep geological repository. The search for a site for the surface infrastructure is carried out in close collaboration with the regions and cantons.
More information is available in the following documents (in German):
- Nagra brochure “Oberflächeninfrastruktur für geologische Tiefenlagerung – Vorschläge zur Konkretisierung”
- Fact sheet on Nagra’s proposals for a surface infrastructure
- Nagra work report NAB 19-08: “Sachplan geologische Tiefenlager Etappe 3: Vorschläge zur Konkretisierung der Elemente der Oberflächeninfrastruktur der geologischen Tiefenlager – Teil 1: Einführung und Grundlagen”
- Nagra work report NAB 19-08: “Teil 2: Standortspezifische Vorschläge”
- Nagra work report NAB 19-15: “Standortunabhängiger Vergleich eines Kombilagers mit zwei Einzellagern hinsichtlich Bau- und Betriebsabläufe sowie Umwelt”