“In line with previous drilling results”

Nagra has completed drilling in Trüllikon. Initial results meet expectations. The second borehole in Zürich Nordost in Marthalen began in early February.

The National Cooperative for the Disposal of Radioactive Waste, Nagra, dismantled the drilling rig in Trüllikon. “It took us around seven and a half months to reach a depth of just over 1300 metres. During the entire drilling procedure, we were able to recover good rock samples and conduct all tests in the borehole as planned”, says Philipp Senn, Nagra’s Deputy Division Head Collaboration Sectoral Plan and Public Outreach.

The rock samples are now being analysed in several laboratories. For all the boreholes, the investigations focus on the Opalinus Clay host rock in which the deep geological repository will eventually be constructed. In particular, Nagra is investigating the thickness, tightness and composition of the Opalinus Clay.

No surprises

First results are already available. Senn draws a positive initial conclusion: “We did not come across any surprises in Trüllikon – the results fit the expected picture.” The Opalinus Clay is over 100 metres thick, very tight and therefore suitable as host rock for a deep geological repository. The composition and tightness of the host rock are similar to those in Benken, where Nagra already drilled in the 1990s. The knowledge gained to date is supplemented with an additional borehole in the Zürich Nordost siting region that is currently being drilled in Marthalen.

The Trüllikon borehole was very successful in technical terms, says Senn: “We began our deep borehole campaign in Bülach where we had to overcome a few technical problems. In Trüllikon, our second borehole, everything worked very well. We were able to benefit from our experience in the Bülach borehole.”

Over 700 visitors at the drill site

Nagra perceived the collaboration with the community of Bülach, local residents and the public in the region as very constructive. “We are very pleased that over seven hundred people came to look over our shoulder during a tour of the drill site”, adds Senn.

Since mid-March, all guided tours have been cancelled due to the coronavirus pandemic, but Nagra was able to continue drilling operations. “Of course, the guidelines issued by the Federal Office of Public Health also apply to the drill site”, Senn states. “In Marthalen, we can continue our work at present – even if greater effort is required. If the situation does not call for more drastic measures, we expect to be able to continue drilling.” The drilling rig used in Trüllikon will now be erected in the Bözberg community (Jura Ost siting region).

The Federal Government has the lead in the site selection process for a deep geological repository. Based on previously conducted investigations, the three regions Jura Ost, Nördlich Lägern and Zürich Nordost have already been identified as suitable in principle for the construction of a repository. Nagra wants to use the deep boreholes to find out which of the three regions is best suited. It is not yet possible to make any statements as to which one this might be.

24/7 hotline and guided tours of the drill site

Nagra has submitted a total of 23 permit applications for deep boreholes in the Jura Ost, Nördlich Lägern and Zürich Nordost siting regions, but has since withdrawn two of them. To date, 17 legally valid permits have been granted. How many boreholes will actually have to be drilled in order to complete the overall geological picture depends on the results of ongoing work, but it is not planned to drill all the boreholes.

Nagra has set up a hotline for questions and concerns of local residents and other interested persons. It is free and operates 24/7 (0800 437 333). There is an information centre at every drill site but these must remain closed during the coronavirus pandemic. Once this extraordinary situation has ended, Nagra will again offer guided tours of the drill site.

More information: Patrick Studer, Head of Nagra’s Media Office: 076 579 36 50. patrick.studer@nagra.ch

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