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

TL;DR

This study investigates how the domain structure of U3O7 influences cracking during UO2 oxidation, revealing that domain-induced stress localization plays a key role in crack formation.

Contribution

The paper demonstrates that the domain patterning of U3O7 grown on UO2 causes stress localization, impacting oxidation-induced cracking, supported by diffraction data and modeling.

Findings

U3O7 layer consists of domains with different orientations

Domain patterning induces stress localization

Stress localization correlates with cracking behavior

Abstract

Cracking is observed when a UO_{2} single crystal is oxidised in air. Previous studies led to the hypothesis that cracking occurs once a critical depth of U_{3}O_{7} oxidised layer is reached. We present some \mu-Laue X-ray diffraction results, which evidence that the U_{3}O_{7} layer, grown by topotaxy on UO_{2}, 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 UO_{2} oxidation and cracking.