| Abstract Scope |
Grain boundaries (GBs) govern the properties of UO2 ceramics pellets used as nuclear fuels and thus determine their performances in reactor. Under irradiation, the fuel is subjected to an intergranular decohesion at the GBs due to the thermomechanical stresses induced by the temperature gradient and to the accumulation of fission gas bubbles. Improving the fuel performances requires a better knowledge of GBs in UO2 and of their fundamental properties including formation energies.
For that purpose, GB energies (ƔGB) were measured, using the thermal grooving method, on polycrystalline samples and on bicrystals with a controlled geometry. For a given GB, similar ƔGB values were found on both materials, suggesting that bicrystals could be used as a model system to better understand the more complex polycrystalline materials. In parallel, ƔGB of similar GBs were simulated at the atomic scale with molecular dynamics. Calculated and experimental values were found in very good agreement. |