The Callovo-Oxfordian layer
France has focused its research on clay and has chosen a deep layer of clay, Callovo-Oxfordian, in the Paris basin to host its high-level and intermediate-level long-lived radioactive waste at some point in the future. A geological cutaway of the area around the future disposal facility site and the laboratory where the research is being carried out shows the Callovo-Oxfordian layer. At a depth of 500 m, between two limestone layers from the Jurassic period, the Callovo-Oxfordian layer is around 130 m thick, uniform and horizontal.