Influence of the U3O7 domain structure on cracking during the oxidation of UO2

Cracking is observed when a UO2 single crystal is oxidised in air. Previous studies led to the hypothesis that cracking occurs once a critical depth of U3O7 oxidised layer is reached. We present some μ-Laue X-ray diffraction results, which evidence that the U3O7 layer, grown by topotaxy on UO2, is made of domains with different crystalline orientations. This observation was used to perform a modelling of oxidation coupling chemical and mechanical parameters, which showed that the domain patterning induces stress localisation. This result is discussed in comparison with stress localisation observed in thin layer deposited on a substrate and used to propose an interpretation of UO2 oxidation and cracking.