Since 1999, the French National Radioactive Waste Management Agency (Agence nationale pour la gestion des déchets radioactifs [ANDRA]) has been carrying out investigations at its Meuse/Haute-Marne laboratory site to study the possibility of implementing an underground repository for high-level and long-lived waste. The geological formation under consideration consists of a stiff clay rock located at a depth of 500 m.
The purpose of this paper is to describe the role of the underground research laboratory and the associated experiments under way within the overall approach of designing a waste repository. The legislative framework indicates that laboratory investigations must focus on the properties of the host rock in its natural state and on its behavior under chemical or mechanical disturbances. Hence, the underground research laboratory is neither a pilot repository project, since the work site of the future repository will be located somewhere else, nor a methodological laboratory, since the experimental and geological-survey methods being used are considered reliable. The purpose of the work conducted by ANDRA is to provide the basic information required to design a safe repository. The research is meant to determine the capability of the clay formation to delay the migration of radionuclides and their release in the biosphere; to propose a repository architecture and building methods for underground structures (excavation and support modes); and to study the physical and chemical disturbances induced by the construction of underground structures and to propose solutions to reduce disturbances and to restore the closest conditions possible to the undisturbed state after shutdown. The Meuse/Haute-Marne underground research laboratory is also used to verify in situ the relevance of the concepts developed to ensure the containment of radionuclides over long time scales and, consequently, to assess the performance of the construction and support techniques that may be applied at an industrial scale in order to implement a repository and the specific techniques capable of reducing the mechanical and chemical disturbances induced by excavation activities.
This paper presents the work and investigations carried out in the underground research laboratory to determine which construction and instrumentation arrangements could be used to implement and operate a waste repository.
