What to do with radioactive waste? In many places, rock formations are being assessed for use as final repositories, including in Switzerland, where Opalinus clay is regarded as a favorable host rock because it repels liquid and swells on contact, which immediately seals leaks. In order to better understand its properties, a new deep borehole was recently started at Mont Terri (canton of Jura) – with scientific support from the Natural History Museum of Bern.
The international research project DEBORAH (Deep borehole to resolve the Mont Terri Anticline Hydrogeology) was initiated by the German GFZ Helmholtz Centre for Geosciences and implemented together with Swisstopo and other partner institutions. The objective is to comprehensively investigate the properties of the Opalinus clay and the rock layers above and below it. The study, a hydrogeological characterization, is intended to determine whether and how the rocks react to water, among other questions.
New maximum drilling depth reached
The drilling is being conducted in the Mont Terri rock laboratory, where there is a motorway tunnel at a depth of around 150 to 200 meters. In the safety gallery – which also serves as the entrance to the rock laboratory – a drilling rig is currently working towards a target depth of 800 meters. On March 12, it passed a depth of 250 meters, marking a new maximum drilling depth for the Mont Terri project. Drilling is currently taking place at a depth of 408 meters. The recovered cores provide valuable information on the age and formation of the rocks. The NMBE investigates and interprets the cores and tags fossils for later extraction. A borehole profile of the different rocks is drawn up and the individual sections are classified according to the formal rock formations. This is followed by the preparation and identification of the fossil finds as well as the scientific analysis. The fossils are stored at the NMBE.
In addition to the aforementioned partners, GFZ Helmholtz Centre and Swisstopo, the Federal Institute for Geosciences and Natural Resources (Germany), Nuclear Waste Services (UK) and researchers from the University of Bern are also involved. Together, they aim to carry out a rigorous assessment of the suitability of potential host rocks for repository sites in Europe.
