The role of crystal orientation in the dissolution of UO₂ thin films

Single crystal [0 0 1], [1 1 0], and [1 1 1]-oriented UO₂ thin films were utilised to investigate the orientational dependence of radiolytic dissolution. The films were exposed to water in the presence of a synchrotron X-ray source to induce dissolution, with X-ray reflectivity (XRR) used to observe changes in morphology as a function of exposure time. The [0 0 1] and [1 1 0]-oriented films were found to corrode at comparable rates, however, the [1 1 1] film was significantly more corrosion resistant, passivating after the initial 90 s dissolution period. This result shows the orientational dependence of UO₂ dissolution, which may have important consequences for theoretical dissolution models.