Ceramic materials as innovative solutions for the HLW disposal containers: global overview and focus on Andra's R&D programme

The concept of a safe geological repository for managing radioactive waste relies on a multi-barrier system comprising both the host rock and various engineered barriers, these latter being referred to as the engineered barrier system (EBS). The robustness of the EBS depends directly on the materials used, which play a crucial role in ensuring its performance. These materials must demonstrate exceptional durability, stability, and compatibility with the host rock and the types of waste expected in the future repository. Moreover, they must remain intact over timescales ranging from hundreds to thousands of years, depending on the repository’s design.

Regardless of the repository concept, a disposal container is required to encase the primary HLW package. Currently, reference materials are primarily metals such as steel or copper. In the case of steel, particularly carbon steel, one significant drawback is the production of H₂(g) during corrosion under anoxic conditions. Minimising or eliminating this phenomenon would facilitate easier and even safer waste management within the disposal facility. This issue is a key motivation for exploring alternative solutions, such as ceramic materials, which do not generate gas when altered.

Research on ceramics as alternatives to metals began in the late 1970s and has periodically regained interest. However, the topic has largely been addressed conceptually, with few concrete research programmes dedicated to tackling this challenge. Since the mid-2000s, Andra has initiated a long-term R&D programme to assess the technical feasibility of a ceramic HLW container that meets the safety requirements of the Cigéo repository concept.

This presentation aims to provide an overview of global research activities related to ceramic options for HLW containers, with a particular focus on the Cigéo concept. Both bulk ceramics and ceramic coatings will be considered. The advantages and limitations of these solutions will be discussed, along with potential approaches to address identified challenges. It is important to note that this contribution does not seek to provide exhaustive details on all related topics but rather offers a scientific and technical overview of ongoing work in this field, which may be of interest to stakeholders in the field of radioactive waste geological disposal.