Expert groups call for Swiss repository studies to include third site

Two Swiss expert groups have today released reports supporting the repository siting proposals put forward by the country's national radioactive waste disposal cooperative Nagra. However, they call for further investigations to be carried out in the Nördlich Lägern region.

The siting regions under investigation (Image: Nagra)

In January 2015, Nagra proposed that further investigations are carried out at the proposed siting regions of Zürich Nordost and Jura Ost in the third and final stage of Switzerland's plan for selecting sites for two repositories: one for low- and intermediate-level waste (LLW/ILW) and the other for high-level waste (HLW). It also said the four other regions under consideration in the second stage - Südranden, Nördlich Lägern, Jura-Südfuss and Wellenberg - will be placed in reserve.

The Cantonal Working Group on Safety (AG SiKa) and the Cantonal Expert Group on Safety (KES) have now said they agree with Nagra that the focus should be on the Opalinus Clay as a host rock for disposal of all waste categories, that the siting regions of Südranden, Jura-Südfuss and Wellenberg should be placed in reserve and that Zürich Nordost and Jura Ost should undergo further investigation in the third stage of the selection process.

However, both groups are in favour of further investigations to be conducted in the Nördlich Lägern region.

Last September, the Federal Nuclear Safety Inspectorate (ENSI) requested that Nagra submit additional technical documentation related to the optimization of the repository depth in terms of safety. Nagra is of the opinion that, while a repository can be constructed safely at a depth of 900 metres, such a depth has disadvantages compared to a depth of 700 metres. In December, Nagra said it would take about six months to prepare the additional documentation. ENSI is expected to make its final evaluation in early 2017.

Nagra has already said, "The geological siting region of Nördlich Lägern for a HLW repository has insufficient underground space in the preferred depth range and there is no possibility of realising the repository at the optimum (from an engineering viewpoint) depth." It added, "Going deeper would provide more space but the engineering challenges would be significant and would lead to considerable impairment of the geological barrier."

However, in December Nagra said it had decided to start planning the investigations for the Nördlich Lägern siting region to avoid delays in case ENSI concludes the region should undergo further investigation, contrary to its own position. This includes preparing an exploration concept for Stage 3 and planning a 3D seismic campaign, as well as deciding on potential sites for deep boreholes.

Nagra is required by federal guidelines to making siting proposals that will provide the basis for the decision to be made by the Federal Council - expected in 2017 - on stage two of the process. The six sites were proposed in November 2011 during the first stage of the selection process. Nagra was required to propose at least two regions to host each of the repositories for further investigations in the third stage.

Up until 2006, much of Switzerland's used nuclear fuel was sent overseas for reprocessing. High level waste, and used fuel from 2006 onwards, is mostly stored at a central interim storage at Wurenlingen. Nagra has been operating an underground research laboratory for a high-level waste repository at Grimsel since 1983.

Researched and written
by World Nuclear News