The mechanical behavior of graphite first wall armor during plasma disruptions was examined by applying fracture mechanics concepts. A fracture mechanics approch is suitable for lifetime evaluation, because the armor surface is expected to be damaged by intense heat load. Two stages are supposed for the lifetime of the armor: crack initiation and crack propagation, which are related to the fatigue life and the energy release rate, respectively. The terms are calculated for the disruption conditions of the Fusion Experimental Reactor (FER), which is referred to as a post JT-60 machine. The analytical results indicate that even though some damage is expected on the armor surface after a few disruptions, unstable failure does not necessarily occur for all disruption conditions.
Crack propagation in first wall of fusion reactor by cyclic thermal stress