Updated State-of-the-Art of WP ConCorD: Deliverable 15.2

A sealed container for the geological disposal of spent nuclear fuel and vitrified high-level waste is the primary component of the deep geological repository that provides complete containment of radionuclides. As such, attention is frequently focused on its lifetime. The lifetime of the container is influenced by materials degradation processes during disposal and is expected to attain a length of of the order of several millennia and, for some container materials, up to one million years. Designing, manufacturing, and predicting the performance of containers over such long periods requires an in-depth understanding of their materials properties, fabrication processes and degradation mechanisms. Scientific and technological progress can improve both the performance of containers as well as the robustness of lifetime predictions. For many national radioactive waste disposal programmes, optimisation of these aspects is of primary importance. In this report the different aspects concerning the degradation of nuclear waste containers and the technological approaches for a better performance are summarized. The information is thematically organized in correlation with the organization of the activities pertaining to the different tasks. The discussion is based on a comprehensive review of the existing knowledge, actualized in view of new insights gained in project ConCorD. Beginning with a discussion on the complexity of the chemical environment created by irradiation, mainly -radiation at the container wall-bentonite interface, the discussion embraces the effects of temperature, saturation, oxygen content and pressure on the corrosion rate, emphasizing the evolution of the corroding interface during the first decades after the sealing. The discussion includes the microbial aspects of the corrosion emphasizing the effects of radiation, temperature, and saturation of bentonite on the survival and growth of microbes and their relevance for the corrosion process, considering copper and ferrous steels as reference materials. A chapter is dedicated to alternative materials and concepts including containers manufactured with ceramic materials, ceramic and metallic protecting coatings, and the evaluation of the use of commercially available metal alloys. The present report is rounded out with a comprehensive review of the existing tools allowing the prediction of long-term barrier integrity, discussing their reliability and limits. Project title: European Joint Programme on Radioactive Waste Management Project Type: European Joint Programme (EJP) EC grant agreement No. 847593 Work Package Title: CONtainer CORrosion under Disposal conditions