(Video in German only)
Throughout the world, the storage of radioactive waste in rock layers deep below the earth’s surface is regarded as the safest solution. In Switzerland too, the Federal Nuclear Energy Act calls for the use of deep geological repositories. A deep geological repository is an underground facility in which radioactive waste can be permanently stored. It ensures the long-term protection of human beings and the environment against harmful effects of radioactive waste, without the need for human intervention (passive safety). Technical and natural barriers prevent harmful radioactivity from escaping from a deep geological repository. The waste is stored in fully sealed receptacles which are completely surrounded by filler material. These function as technical barriers, while the dense layers of surrounding host rock form the natural barrier.
In addition to the main repository for the storage of radioactive waste, a deep geological repository also has to include a pilot storage zone below the surface. In order to secure the operation of a deep geological repository until it is definitively sealed, the facility requires various infrastructure components, for example for waste transport, storage and disposal, transport of personnel and for intervention on the surface in the event of an emergency. Access structures (ramps or galleries) connect the underground storage zones with the surface facilities.
Test zones are separate components of a deep geological repository. They are used for testing the safety-relevant properties of the host rock and technical barriers, as well as for trialling safety-relevant methods for depositing or recovering the waste material and for filling and sealing the engineering structures.
Pilot storage zone
The pilot storage zone is entirely separated from the deep geological repository. This is where the behaviour of waste, filler material and host rock is monitored until the expiry of the observation period.
Throughout Europe, crystalline, clay and salt rock formations are regarded as potentially the most suitable host rock for the disposal of radioactive waste in deep geological repositories. There is no single ideal host rock – each formation has its own advantages and disadvantages. The host rock must be able to guarantee the necessary degree of safety for the deposited waste and the installed technical barriers, as well as ensure the long-term geological stability of the site. Extensive studies carried out within the framework of stage 1 of the Deep Geological Repositories Sectoral Plan have shown that, in Switzerland, it is clay-rich sediment layers (opalinus clay, “Brauner Dogger”, “Effinger” layers and Helvetic marl formations) that are best able to meet the stringent requirements. Crystalline rock formations are brittle, and during the uplift of the Alps in Switzerland they were thus susceptible to fracturing and fissuring, as a result of which water is able to circulate at great depths below the ground. The salt rock formations in Switzerland are too small, and when they lie close to the surface they are mined as a raw material. Salt domes such as those found in northern Germany do not exist in Switzerland.
- Deep Geological Repository. Fact Sheet
(PDF, 204 KB, 22.11.2017) ID: 8885 | 340
- Host Rock. Fact Sheet
(PDF, 498 KB, 22.11.2017) ID: 8889 | 365
- Beitrag zur Entsorgungsstrategie für die radioaktiven Abfälle in der Schweiz
(PDF, 574 KB, 01.10.2002) ID: 537 | 336
- Disposal Concepts for Radioactive Waste, final report
(PDF, 396 KB, 31.01.2000) ID: 322 | 336
Last modification 05.11.2020