Glossar

 

Nördlich Lägern

The Federal Council decided on 21st November 2018 that the Nördlich Lägern siting region (Cantons Zürich and Aargau) should also be investigated further in Stage 3.

The region to the north-west of Bülach was confirmed by the Federal Council in Stage 2 as one of the three potential siting regions for a deep geological repository.

Geological siting region Nördlich Lägern

In Nördlich Lägern, the siting regions for a L/ILW and HLW repository are located in the precursory folding zone and are delimited geographically by the national border along the Rhine river and geologically by a regional fault zone to the north and south, as well as by the depth of the host rock to the south. The rocks in the north-east show less quiet bedding conditions compared to the Zürich Nordost siting region.

The geological siting regions for a L/ILW and HLW repository or a combined repository in Nördlich Lägern with the main underground connection area, the potential L/ILW and HLW disposal zones, the perimeter for the auxiliary access facilities and the siting areas NL-2 and NL-6 for the surface facility.

Siting communities

Canton Zürich: Bachs, Bülach, Eglisau, Glattfelden, Hochfelden, Neerach, Niederweningen, Oberweningen, Schleinikon, Schöfflisdorf, Stadel, Weiach

Canton Aargau: Fisibach, Schneisingen, Siglistorf

Next steps in the site selection process

Stage 3 is currently underway. More information is available on the page "Site selection".

Starting-point for concretising the surface infrastructure

At the end of Stage 2 of the Sectoral Plan process, the Federal Council designated two areas for the surface facility in the Nördlich Lägern region (NL-2 and NL-6). The Federal Council indicated that narrowing down to one siting area should be done within the framework of regional participation. The main underground connection area is located in the area between "Haberstal" and Windlach at the north-west edge of the potential disposal zones and will be accessed with a shaft as the main access in the NL-6 area. An operations and a ventilation shaft will be located within the perimeter for the auxiliary access facilities. Based on this, Nagra has made four proposals for collaboration with the region.

The concrete proposals can be found in the factsheet on Nördlich Lägern (in German).

In the Nördlich Lägern siting region, the Opalinus Clay is the host rock for disposal of radioactive waste.

In the Nördlich Lägern siting region for L/ILW, two potential host rocks – the Opalinus Clay and the 'Brauner Dogger' – were identified in Stage 1. In Stage 2, Nagra carried out a safety-based comparison for these formations. Overall, both host rocks show a good barrier function, but for the 'Brauner Dogger' there are clear disadvantages compared to the Opalinus Clay. The Opalinus Clay was therefore identified as the priority host rock in the L/ILW siting region.

The Opalinus Clay is around 173 million years old and is suitable as a host rock for a L/ILW and a HLW repository. The Opalinus Clay layer is around 110 metres thick in the L/ILW and HLW siting regions and makes the main contribution to the barrier function of the overall system. In the Nördlich Lägern siting region, the confining units above and below the Opalinus Clay ('Brauner Dogger' clay sequence, the Effingen Member and the clay-rich Lias) also make a significant contribution to the barrier function. For the upper confining units, uncertainties have to be considered in the evaluation, but these have no influence on the selection of the siting regions.

In the siting regions for L/ILW and HLW, Nagra assessed the available space in the preferred depth range as being unfavourable. This was underpinned by the knowledge base for the safety-based comparison in Stage 2. The available space is larger at greater depth, but it would be difficult in construction engineering terms to realise a repository at such depth. During construction, the unfavourable depth could lead to significant damage to the geological barrier. In its reviewing of Nagra's documentation, ENSI reached a different conclusion on certain points, relating inter alia to the evaluation of maximum depth and available space. Both are particularly relevant for evaluating the siting regions for L/ILW and HLW in Nördlich Lägern.

Geological profile from north-north-east to south-south-west through the Nördlich Lägern siting region. The arrow marks the Opalinus Clay.

Geological profile showing the rock strata occurring in the Nördlich Lägern region.

In the third stage of the site selection process, the three siting regions remaining in the process are investigated in greater detail and then compared with one another. The exploration programme includes Quaternary investigations and deep boreholes. The latter will complete the overall geological picture of the siting region. The focus of the geoscientific investigations in the deep boreholes is on the depth, thickness, permeability and composition of the Opalinus Clay host rock in which the repository will be constructed. The properties of the confining rock units above and below the Opalinus Clay are also of particular interest.

Questions about the siting region

Questions on the Sectoral Plan process: Swiss Federal Office of Energy (SFOE)

WWW.BFE.ADMIN.CH

 

Questions on safety: Swiss Federal Nuclear Safety Inspectorate (ENSI)

WWW.ENSI.CH

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