Innovative and new container/canister materials under disposal fields conditions: manufacturing feasibility and improved durability (InCoMand)
Objectives
The WP aims at identifying and qualifying novel materials for the HLW containers/canisters, as well as providing a deeper knowledge of both traditional and novel materials long-term durability in, as realistic as possible, field conditions.
Description of the WP
Deep geological disposal of high-level waste (HLW) will subject the container to various challenges, corrosion resistance being one of the most crucial. HLW components lifetimes are typically calculated based on the time-dependent corrosion behaviour alone, with the implicit assumption that the component has been designed to remain structurally stable over extremely long periods. However, for some component materials and designs, there may be significant interactions between mechanical and corrosion degradation modes that could affect the ultimate failure time. Even though the durability of several component materials subjected to corrosion processes have been previously studied in detail, the interaction of mechanical processes and corrosion calls for further study, and assessment of the impact of joint degradation modes on component lifetimes will result in a more robust and defensible safety case. Besides, as corrosion occurs in a thin interfacial surface layer between the component outermost surface and the environment, specific R&D work is required to understand the long-term performance controlled by the entire engineered barrier system (EBS). Indeed, this latter is complex, made of different materials (excluding here the containers), for instance the host rock and cement-based materials (backfills, buffers), and characterized by various, impactful conditions such as the water chemistry, the microbial activity, the stress load, the temperature, the radiation sources…).
Another approach to tackle the corrosion issue is to prevent and/or minimize it, thereby ensuring an even safer disposal. In this approach, materials much less prone to corrosion (e.g., ceramic materials) can be used to fabricate the containers. Alternatively, protective coatings can be applied to current selected reference materials. Both ways require selection of the relevant materials and of the fabrication/deposition methods and validation of the materials durability under realistic, accelerated field conditions.
Outcomes
The increased understanding will contribute the following SRA drivers:
Scientific insight: Joint and simultaneously operating degradation mechanisms are demanding to tackle scientifically. It is foreseen that clarifying these mechanisms within the WP will have a significant impact on pushing the state-of-the-art modelling and understanding of those mechanisms beyond the current state.
Innovation for optimization: Improvements of current reference solutions are intensely investigated across Europe. Those improved solutions must rely on appropriate fabrication technologies that can be adapted to mass-production of containers, which requires to increase the TRLs of such technologies. These latter must also be financially reasonable, and material supply chains must be reliable. The proposed LCC/LCA analyses make the first effort to capture the economic and technical aspects of advanced HLW container solutions.
Knowledge management: The proposed WP will make a significant effort in training new scientists, in reporting the state-of-the-art in such a form that it is easily accessible, and to disseminate the results both through peer-reviewed papers and during lectures at the Master and Doctorate levels.
Tailored Solutions: The WP will address HLW disposal challenges across Europe from scientific and economic points of view. It is foreseen that significant added value can be obtained when the work on metallic and ceramic materials are examined in the same WP and towards a shared, common goal.
Implementation of safety: the increased understanding on canister behaviour will increase the confidence of life assessment and ensures long-term safety.
Societal Engagement: improving containers is a clear sign to the stakeholders and society that the scientific community is continuously working hard for ensuring the best safety conditions of the final disposal.
