Preliminary results of Nagra’s deep borehole campaign
Since 2019, Nagra has been drilling deep boreholes to investigate the geological underground in the Jura Ost, Nördlich Lägern and Zürich Nordost siting regions. Initial results are now available from all three regions. “The results confirm that it is possible to construct a safe repository in all three regions”, states Tim Vietor, Head of Geology and Safety and member of the Nagra Executive Board. In all three siting regions, there is also sufficient space for the arrangement of a combined repository, i.e. a repository in which all types of waste (low-, intermediate- and high-level) can be disposed of.
In all three regions, the underground shows the required properties: each region has a layer of Opalinus Clay over one hundred metres thick that is very tight and quietly bedded. The Opalinus Clay is the rock that will eventually host the deep geological repository and is the most important safety barrier that contains the radioactive waste over a long time period.
Similar host rock, differences in the confining geological units
The regions differ in some respects. For example, the Opalinus Clay layer is not always located at the same depth, and the rock formations lying above and below the Opalinus Clay can vary. These so-called confining geological units can also contribute to waste containment.
In the Jura Ost region, two boreholes are currently being drilled in the community of Bözberg. The first borehole will be completed soon and the second one by the end of the year. These two boreholes should complete the picture of the underground for the upcoming site selection. “So far, everything points to confirmation of our previous understanding of the region. In Jura Ost, the Opalinus Clay is 120 metres thick and very tight. At the moment, we believe that we will not need a further borehole in this region”, says Vietor.
With the boreholes in Trüllikon and Marthalen as well as the earlier one in Benken, the picture of the underground in Zürich Nordost is now complete. Nagra may drill one more borehole in the Zürich region to clarify some details.
Nördlich Lägern better suited for repository construction than expected
Nagra is pleased with the results of the first deep borehole in Nördlich Lägern: the Opalinus Clay is very tight. A coral reef was drilled through above the Opalinus Clay, but it is also tight.
In Bülach, the Opalinus Clay is located at a greater depth (around 900 metres) than in the other regions. Another result from Bülach is also positive: “We initially expected it to be difficult to construct a deep geological repository and its many tunnels at this depth. However, investigations have shown that this is feasible, and that a repository can therefore be constructed in this region”, Vietor explains. The overall picture of Nördlich Lägern is not yet complete. Early next year, two further boreholes will be drilled in the community of Stadel.
Numerous laboratory analyses and at least two more boreholes are still pending. In 2022, Nagra expects to announce the site for which it will submit a general licence application for a deep geological repository. The lead in the site selection process lies with the Federal Government.
More information: Patrick Studer, Head Nagra’s Media Office: 076 579 36 50, firstname.lastname@example.org
According to Swiss nuclear energy legislation, the producers of radioactive waste are responsible for its safe management and disposal. In 1972, the Federal Government and the nuclear power plant operators set up the National Cooperative for the Disposal of Radioactive Waste (Nagra) to perform this task. Nagra, which has its headquarters in Wettingen (AG), is the national technical competence centre in the field of deep geological disposal of radioactive waste.
Out of a strong sense of responsibility for the long-term protection of man and the environment, 130 employees are involved daily in performing this important work. The high level of competence is secured by targeted research programmes in two Swiss underground rock laboratories and intensive international collaboration.