Created in 2000, the Andra Underground Research Laboratory in Meuse / Haute-Marne is in constant evolution. Its experimental galleries now reach nearly two kilometers in length. Let's look back on the experiments conducted for nine years, 500 meters below ground level.
Here, neither white coats nor microscopes, as one would expect to see in a traditional scientific or chemistry laboratory, but hard hats, tunnels and a lot of cables. This underground laboratory, however, is a high-level technological and scientific tool essential for the design of Cigéo, the geological disposal facility project.
A technological demonstrator
After having reached the clay layer in 2004 and then studied the geology of the site, the following phase, running from 2009 to 2018, focused on digging, retaining and sealing techniques, in particular to evaluate their impacts on the surrounding rock. Several machines have been used: the Hydraulic Rock Breaker (HRB), the Road Header (a kind of huge milling cutter with spikes) and even the Tunnel Boring Machine (TBM). New techniques have also been tested, such as the one using tunnel lining segments, (reinforced concrete arches supporting the galleries) with compressible shells designed to damp the forces exerted by the rock on the retaining structures. These studies are essential to ensure the safety of deep disposal facility. They are the subject of numerous measurements, before, during and after the work, thanks to twenty thousand sensors distributed in the Laboratory.
This long phase of experiments also allowed to better understand how the different materials (those used for the waste packages or to build the galleries and the cells that will host them, as well as the clay where they are dug) interact with each other on a very long time scale. Thanks to various experimental devices, the corrosion rates of the steels, the durability of concrete in contact with the clay were tested. These new measurements confirm the exceptional qualities of the Callovo-Oxfordian clay layer, capable of limiting the dispersion of radioactive elements in the environment for hundreds of thousands of years. Experiments will continue as part of a new experimental phase. It will study equipments that are increasingly closer to the one that will be used on the deep geological disposal project, such as a prototype cavern for long-lived intermediate-level waste (ILW-LL), or backfill and sealing