Glossar

 

Zürich Nordost

The Federal Council decided on 21st November 2018 that the geological siting region Zürich Nordost (Cantons Zürich and Thurgau) should undergo further investigation in Stage 3.

The region 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 Zürich Nordost

In Zürich Nordost, the siting region is located in the eastern Tabular Jura and is bounded geographically by the national border along the Rhine river to the west and north-west and geologically by the Neuhausen Fault to the north-east, as well as by the maximum depth of the host rock to the south-east. The Opalinus Clay host rock has a large lateral extent and the rock layers show very quiet bedding.

The geological siting regions for the L/ILW and HLW repository or a combined repository in Zürich Nordost 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 ZNO-1 and ZNO-6b for the surface facility.

Siting communities

Canton Zürich: Benken, Dachsen, Flaach, Flurlingen, Kleinandelfingen, Laufen-Uhwiesen, Marthalen, Ossingen, Rheinau, Trüllikon, Truttikon

Canton Thurgau: Schlatt

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 identified an area for the surface facility in the Zürich Nordost siting region (ZNO-6b). Nagra's investigations revealed that, in the area ZNO-6b, there was a local groundwater deposit. Nagra would prefer to construct the surface facility above this groundwater level, which would mean that the buildings would be sunk less deep into the underground, making them more visible at the surface. As a result, Nagra proposed the nearby siting area ZNO-1 as an alternative for discussion as the structures in this case would be less visible. The main underground connection area is in the area of Isenbuck – Berg and east "Rinauer Feld" and lies on the western edge of the potential disposal zones. Accesses for construction and for the operations shaft and ventilation shaft have to be identified within the perimeter for the auxiliary access facilities. Based on this, Nagra made four proposals for collaboration with the region.

The concrete proposals can be found in the factsheet on Zürich Nordost (in German).

The Opalinus Clay in the Zürich Nordost siting region is the host rock for disposal of radioactive waste.

In the Zürich Nordost 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 Zürich Nordost 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 Zürich Nordost siting region, the confining units above and below the Opalinus Clay (clay-rich Lias, 'Brauner Dogger' clay sequence and the Effingen Member) also make a significant contribution to the barrier function. The geological situation is also favourable with respect to long-term stability. Sufficient space is available in the L/ILW and HLW siting regions in the preferred (from a technical viewpoint) depth range.

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

 Geological profile showing the rock strata occurring in the Zürich Nordost 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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