Influence of creep and geometry on strength of irradiated graphite components

The proposed work aims to improve the understanding of graphite fracture and irradiation creep behaviour by studying large specimens extracted from a reactor at end-of-service. This uniquely will enable valid fracture and creep data to be determined on material that had seen reactor conditions to high dose and weight loss conditions. Current data are determined on small specimens that are either unirradiated or irradiated in materials test reactors. In particular, the likely life-limiting failure mode is through a process known as keyway root cracking. Here a crack initiates at a sharp re-entrant corner; to study this failure mode in particular requires specimens of sufficient size to give a valid range of notch geometries. In addition, the relaxation of stress by irradiation creep is a key process to mitigate processes at sharp corners. No work on irradiation creep has been performed on corner geometries or at high tensile strain; both of these will be addressed in the current proposal. The results will allow the continued safe operation of reactors, enabling low carbon energy to be produced in the UK.