Assessment of defects in EUROFER 97 first wall/blanket structures taking into account its viscoplastic behavior

The assessment of cracks situated in areas operating at high temperature requires reliable methods based on the elasto-viscoplastic fracture mechanics. An important step thereby is the determination of the C-integral as an objective crack loading parameter whose evolution over time is strongly dependent on the material behavior assumed. In this work, different material models for EUROFER 97, a standard elasto-plastic/creep model and a new elasto-viscoplasticity model developed recently for RAFM steels, are applied calculating the C-integral and its evolution for cracks in simple geometries as well as in first wall/blanket mock-ups. The calculations are carried out performing finite element simulations. The results are then compared with those determined using the simple formulae of the R5-code (British Standard) to verify its applicability and determine its limits.