Site proposed for Swiss repository

Six sites were proposed in November 2011 during the first stage of the process - which began in 2008 - for selecting sites for two repositories: one for low- and intermediate-level waste (LLW/ILW), the other for high-level waste (HLW). The repository for LLW/ILW is planned to be in operation by 2050, with the one for HLW planned to be operational ten years later.

Stage two of the site selection process, which began in late 2011, aimed to narrow down the sites under investigation to at least two for each of the repositories. Nagra proposed in January 2015 that further investigations be carried out at the proposed siting regions of Zürich Nordost and Jura Ost in the third and final stage of the selection process. It said the four other regions under consideration in the second stage - Südranden, Nördlich Lägern, Jura-Südfuss and Wellenberg - would be placed in reserve. However, in December 2016, the Swiss Federal Nuclear Safety Inspectorate (ENSI) proposed that the Nördlich Lägern region also be included in the final stage.

Following the completion of the second stage of the site selection process, the Federal Council made the decision at a meeting in November 2018 to include the Nördlich Lägern region in further investigations. In addition, the regions of Jura-Südfuss, Südranden and Wellenberg remain reserve options.

Nagra has now proposed that Nördlich Lägern should host a combined repository that is suitable for all types of radioactive waste. The entrance to the repository, the so-​called surface facility, would be constructed in the Haberstal area in the community of Stadel in canton of Zürich.

How the repository surface facility could appear (Image: Nagra)

Nagra said its investigations showed that it was possible to construct a safe deep geological repository in all three siting regions - Jura Ost, Nördlich Lägern and Zürich Nordost. However, the Opalinus Clay in Nördlich Lägern offers the greatest geological barrier effect, the best stability of the rock layers and a high degree of flexibility for the layout of the underground repository in comparison with the siting regions Jura Ost and Zürich Nordost.

Nagra has also decided not to build the fuel element packaging facility in the siting area itself, but on the site of the existing Zwilag interim storage facility in Würenlingen in the can­ton of Aar­gau, adjacent to the Paul Scherrer Institute.

Most of Switzerland's HLW is currently held in transport and storage casks at the Zwilag facility, with a smaller percentage at the interim storage facility at the Beznau nuclear power plant (Zwibez). Before its emplacement in the planned deep geological repository, the waste will be transferred to smaller disposal canisters in the encapsulation plant.

Nagra said it will now prepare the general licence applications for the repository and the encapsulation plant, which it expects to submit to the Federal Council in 2024. The authorities and the federal government will review these applications before the Federal Council and parliament make their decisions. This approval, expected around 2030, will be subject to an optional referendum, with the Swiss voters having the final say. Nagra said it is likely to be another 30 years or so before it can start waste emplacement operations.

"Nagra's siting proposal is an important milestone in the project of the century of deep geological disposal," said Nagra CEO Matthias Braun. "Today we know which site is safest for a deep geological repository. This is not only important for us, to conclude all these years of research, but for the entire Swiss population."