Irradiation effects on the fracture properties of UO2 fuels studied by micro-mechanical testing

Micro-cantilevers were prepared with a dual beam microscope SEM/FIB on different fresh and irradiated Pressurized Water Reactor (PWR) UO2 fuels. Their local fracture properties (fracture toughness and fracture stress) and Young's moduli were determined by bending tests, carried out with a nano-indenter in situ of a SEM chamber. Different microstructural features were characterized by testing three crystalline planes into single grains and grain boundaries. Inside grains, irradiation has a limited effect on the measured properties, whereas irradiation leads to a clear drop of the grain boundary resistance, related to the presence of irradiation defects. •Micro-cantilever bending method was applied to fresh and irradiated PWR UO2 fuel samples.•Two fracture parameters were measured at a local scale: fracture toughness and fracture stress.•The local Young's modulus was evaluated inside fuel grains for different crystalline orientations.•The effect of irradiation on the measured properties of the fuel was evaluated.•The influence of defects on the measured fracture stress was also investigated.