Contribution of HADES URL to the development of the Cigéo project, the French industrial centre for geological disposal of high-level and long-lived intermediate-level radioactive waste in a deep clay formation

Abstract In the 1980s, HADES was the first URL dedicated to the study of the geological disposal of radioactive waste in a deep clay formation, the Boom Clay. It was not until the early 2000s, after a siting process, that Andra implemented the Meuse/Haute-Marne URL, in the Callovo-Oxfordian formation at a depth of about 500 m in order to develop the Cigéo project (French industrial centre for geological disposal). Andra therefore relied heavily on the work carried out in HADES, through numerous cooperation projects (participation in in-situ experiments) both between Andra and ONDRAF/NIRAS & SCK CEN (Euridice) and/or with Mont Terri consortium, and within European projects (CLIPEX, RESEAL, etc.). This was driven by a dual objective: (a) to prepare its own experimental programmes in the Meuse/Haute-Marne underground laboratory (methodology, experimental devices and protocols, etc.), and (b) to have general knowledge on the behaviour of argillaceous rocks, in particular in terms of similarity and differences between the various argillaceous rocks. The paper illustrates the contribution of HADES to the Andra programme. This concerns the characterisation of the claystone behaviour, host rock and swelling clay-based seals (HM, THM, EDZ, etc.), and the design and the behaviour of underground structures and seals in deep clay formation (constructability, lining/support, etc.).