Enhancements in the structural integrity assessment of plasma facing components

This paper provides an overview of analysis methodologies that can be employed to overcome many of the issues associated with the structural integrity assessment of plasma facing components. These issues arise from the multiple materials construction of the plasma facing components (tungsten armour, CuCrZr heat sink and copper interlayer) making direct application of standard (elastic) structural integrity assessment methods problematic. Example analysis results are used to illustrate these issues, from which it is concluded that PFC structural integrity assessment requires the use of elastoplastic analysis methods, and that this should include: a manufacturing simulation cycle to account for residual stress (and manufacturing strains); pre and post irradiation simulation cycles (with appropriate material models) to correctly assess accumulated ductility usage, and the study of plastic strain in tungsten recrystalised layers to anticipate deep cracking. The issues raised by stress/strain singularities (caused by dissimilar material joints) and multiple ratcheting mechanisms (global, local, material and bi-material ratcheting) are also discussed and proposals made.