Effects of irradiation on mechanical properties of nuclear UO2 fuels evaluated by Vickers indentation at room temperature

Vickers indentation was used to evaluate the hardness and apparent fracture toughness of unirradiated irradiated UO2 fuels, with objective determine effects irradiation on mechanical properties. Indentation tests were realized at room temperature standard doped in a pressurised water reactor up burnup 81.6 GWd/tM. For highest burnups, fuels had restructured high structure (HBS) periphery pellets. More than 100 valid impressions for determination obtained each fuel. The both increased local burnup, due defects such as dislocations fission products but decreased when fuel into HBS. Valid crack patterns only indentations inside large grains or fuels. non-restructured shown increase quickly during first cycle then constant increasing burnup. This mainly decrease length from corner indents, attributed interactions cracks bubbles product precipitates associated residual stresses. In HBS, short indents that followed grain boundaries small led values. However, use literature equations calculate porous samples HBS is questioned. All clearly illustrated weakness