In the future, Switzerland will dispose of its radioactive waste in a deep geological repository. This will comprise both underground and surface facilities. The decision on where to construct the repository depends on geology. The radioactive waste will be safely enclosed in rock formations at a depth of several hundreds of metres for a very long time period. The most important rock formations are the Opalinus Clay and those lying directly above and below it. They can also be found in the Nördlich Lägern region where they have favourable properties.
Nördlich Lägern is one of three potential siting regions that we have been investigating in detail since 2008 within the framework of the Sectoral Plan for Deep Geological Repositories of the Federal Government. We now know which properties the rocks have and how much space is available for a repository. We work with the region in deciding where to locate the surface facilities. Aside from Nördlich Lägern, Jura Ost and Zürich Nordost are also potential siting regions. As part of the Sectoral Plan process, we compare these regions to identify which one is most suitable for a repository. In a few years, the Federal Council will decide where the repository will be constructed.
Overview: What would a repository in Nördlich Lägern look like?
For the Nördlich Lägern siting region located to the north-west of Bülach, we have developed a repository project adapted to the region. This incorporates the insights from our geological investigations and the results of our collaboration with the region.
The geological siting region delineates the underground rock area suitable for the disposal of radioactive waste. Areas with geological fault zones are avoided for repository construction. By investigating the underground (particularly with 3D seismics), we were able to identify such fault zones. Priority is given to the investigation perimeter that includes the most suitable part of the rock area and is designated to host the emplacement rooms for the waste. For this reason, it was investigated in depth. The main underground connection area comprises the endpoint for accesses from the surface and the starting point for accesses to the emplacement rooms.
The auxiliary access facilities are located at surface level. The auxiliary access facility for ventilation lies within the blue perimeter and supplies the underground section of the repository with fresh air. The auxiliary access facility for operations serves to transport building materials and people as well as to supply power and water. Just like the surface facility at the NL-2 or NL-6 site, the auxiliary access facilities form part of the surface infrastructure of a deep geological repository. In the surface facility, the waste is prepared for emplacement and then transported below ground. If the surface facility were to be constructed at the NL-6 site, the fresh air supply and the auxiliary access facility for operations could be merged into one auxiliary access facility, NL-BL1.
Detailed information on the Nördlich Lägern siting region (in German)
- Nagra brochure “Oberflächeninfrastruktur für geologische Tiefenlagerung – Vorschläge zur Konkretisierung”
- 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”
State-of-the-art investigation methods used to complete overall picture
In winter 2016/17, we carried out large-scale 3D seismic measurements to obtain an image of the underground in Nördlich Lägern. This method can be compared to medical ultrasound images or an echo sounder used on ships. The seismic images we obtained provided important information on the structure of the rock formations. We were also able to identify the presence of geological fault zones and assess the space available for a repository.
We drilled five deep boreholes in Nördlich Lägern: Bachs (2021), Stadel-2 (2021), Stadel-3 (2020/21), Bülach (2019) and Weiach (1983). These reached a depth of several hundred metres and went far below the Opalinus Clay that will host the waste. By drilling these boreholes, we were able to obtain samples from various rock layers and determine their properties. Investigations showed that the Opalinus Clay, but also the rock formations lying directly above and below it, are very tight. The deep boreholes also revealed the depth at which the individual layers are located.
To provide long-term safety, the emplacement rooms of a deep geological repository that hold the waste must lie sufficiently deep below ground. Only then is the repository safe from erosion caused by rivers and glaciers. Traces of past erosion processes are also visible in the Nördlich Lägern siting region. Glaciers cut deep troughs into the landscape, and glacial advances will also occur in the future. To learn more about the impact of glaciers and rivers and to develop future scenarios, we conducted Quaternary investigations. With these, we were able to investigate the topmost – and our planet’s most recent – rock layer located just beneath the surface. Quaternary investigations primarily include boreholes that are drilled to a depth ranging from a few dozen metres to around three hundred metres. In 2019, we drilled in Hochfelden-Strassberg.
With the most recent investigations, we were able to complement and complete the already existing knowledge of the geological underground in Nördlich Lägern. With the conclusion of the Bachs borehole, we will be in possession of a comprehensive image of the geological underground. New knowledge of the underground allowed us to develop the Zürich Nordost repository project. We have also thoroughly investigated the other two potential siting regions, Jura Ost and Zürich Nordost, and can now objectively compare the three regions with one another.
Collaboration on the site for the surface infrastructure
Where will the buildings at the surface and accesses for a deep geological repository eventually be constructed? These are the questions Nagra is addressing together with the siting regions. Our dialogue partners are the Nördlich Lägern Regional Conference, Cantons Zürich and Aargau as well as representatives from neighbouring Germany. These can express their views on the proposals that we publish as a basis for collaboration and discussion. By collaborating from this early stage, the responsible Swiss Federal Office of Energy ensures that the needs of the Nördlich Lägern siting region are considered to the greatest extent possible.
Websites of the region’s representatives (in German)
In 2019, we published specific proposals for the Nördlich Lägern region in what the surface infrastructure might look like in this region. The proposals are the result of previous collaboration with the region. Together with the other siting regions, the issue of where to place the encapsulation plant for spent fuel assemblies was also discussed. The Nördlich Lägern Regional Conference, Cantons Zürich and Aargau as well as representatives from Germany have worked intensively on the placement of the surface infrastructure and have submitted their position statements. These form the basis for the further concretisation of the surface infrastructure with a view to the general licence application.
Position statements of the Nördlich Lägern Regional Conference and Cantons Zürich and Aargau (in German)
- Position statement of the Nördlich Lägern Regional Conference on the surface infrastructure
- Media release on the position statement of Canton Zürich on the surface infrastructure
- Media release on the position statement of Canton Aargau on the surface infrastructure
- Joint statement on the siting issue for the encapsulation plant for spent fuel assemblies
In 2022, we will announce which siting region we consider most suitable for a deep geological repository. We will then submit a general licence application for this region. Our work is conducted in line with federal authority stipulations as set out in the Sectoral Plan for Deep Geological Repositories. This forms the basis for the decision of the Federal Council, which will decide on the site around 2029 and submit its decision to the Federal Assembly for approval around 2030. Once the definite site has been confirmed, we will plan and construct the deep geological repository there.