MYRRHA, ALFRED and also ITER will use austenitic stainless steels as structural and functional materials. Particularly, fuel claddings will be made of this class of materials. Production of the claddings involves welding. Understanding the influence of heavy liquid metal environment on these components, including the welded joints, is an important part in the qualification procedure of the reactors. Welding involves local melting and solidification, and creates heat-affected zones. In the material, locally different microstructural transformations occur. Additionally, the production process of the tubes gives rise to anisotropic material behaviour. This anisotropy, in turn, affects the component’s structural response in terms of stress, deformation, damage and fracture. Despite these complexities, the ultimate objective of welding is to provide a sound joint with equal or better performance than the base metal . Moreover, to be used in reactors, guaranteeing the mechanical properties of fuel cladding tubes and their welds in a heavy liquid metal (lead-bismuth eutectic or LBE) environment is of major importance. A major issue is the occurrence of corrosion, which reduces the burst pressure of the cladding. An accurate predictive tool of the above to ensure the structural integrity of the fuel claddings (and, particularly, their welds) is crucial during the design stage.
This PhD project aims to understand and predict the pressure bearing capacity of thin walled fuel cladding tubes, taking into account the high temperature LBE environment, the presence of texture anisotropy, the heterogeneity of microstructures within the weldment and the presence of corrosion damage. This involves a multidisciplinary (materials science and mechanics) approach consisting of microstructural investigations, construction of anisotropic material models, development of a finite element model for the fuel cladding tube and experimental validation assisted by 3D digital image correlation.