Résumé
In irradiated polycrystalline uranium dioxide (UO2), the pressure generated at high temperature by the noble gases inthe intergranular bubbles as well as the thermomechanical stresses due to temperature gradients cause the fracture ofthe grain boundaries. In this study, one analyzes through atomistic calculations of static and molecular dynamics typethe properties of three UO2 grain boundaries and their behavior under uniaxial tensile loading up to fracture. In theseatomistic simulations, the interactions between atoms are described using a many-body variable charge potential.Structural analysis, performed on the three grain boundary structures under uniaxial tensile stresses and over a widetemperature range, reveals no source of plasticity. This suggests a brittle behavior at fracture, in agreement withrecent experimental studies carried out on micrometer size specimens containing grain boundaries. A method basedon thermodynamic considerations is used to build normal cohesive zone laws for the UO2 grain boundaries usingmolecular dynamics simulation data. The cohesive zone laws will be employed in a future study in failure simulationsat higher scales.