Corrosion of nuclear fuel cladding by the water in the primary circuit as it passes through the reactor leads to hydriding. Delayed hydride cracking (DHC) is likely to occur later, during dry storage. Such cracking requires a pre-existing defect and a thermo-mechanical history that enables the following iterative mechanism to be set in motion: hydrogen diffusion, precipitation of hydrides at the crack tip and rupture of the embrittled zone. During a previous thesis carried out in the host laboratory, an original procedure combining experiments and numerical simulations using finite elements was used to determine the toughness of unirradiated relaxed Zircaloy-4 cladding in the event of DHC, and to report on the effect of mechanical loading and temperature on the incubation time and cracking speed between 150°C and 250°C. The aim of this thesis is to apply this procedure to a more modern cladding material (recrystallised M5) and to develop fine-scale microstructure modelling that can account for the effects of texture (crystallographic and morphological), propagation direction and plane, and irradiation on DHC.
Corrosion of nuclear fuel cladding by the water in the primary circuit as it passes through the reactor leads to hydriding. Delayed hydride cracking (DHC) is likely to occur later, during dry storage. Such cracking requires a pre-existing defect and a thermo-mechanical history that enables the following iterative mechanism to be set in motion: hydrogen diffusion, precipitation of hydrides at the crack tip and rupture of the embrittled zone. During a previous thesis carried out in the host laboratory, an original procedure combining experiments and numerical simulations using finite elements was used to determine the toughness of unirradiated relaxed Zircaloy-4 cladding in the event of DHC, and to report on the effect of mechanical loading and temperature on the incubation time and cracking speed between 150°C and 250°C. The aim of this thesis is to apply this procedure to a more modern cladding material (recrystallised M5) and to develop fine-scale microstructure modelling that can account for the effects of texture (crystallographic and morphological), propagation direction and plane, and irradiation on DHC.