Effect of grain-boundaries on uranium and oxygen diffusion in polycrystalline UO2

The influence of grain-boundaries on uranium and oxygen diffusion in polycrystalline UO2 has been investigated. Our results show that between 1498 deg. C and 1697 deg. C, in H2 atmosphere, uranium diffusion in UO2 grain-boundaries is about five orders of magnitude greater than uranium volume diffusion, in the same experimental conditions. Between 605 deg. C and 750 deg. C, in H2/N2/H2O atmosphere, the oxygen diffusion coefficients measured in polycrystalline and single crystalline UO2 are similar, and correspond to the volume diffusion