[SY-B9] Symposium B-9

[SY-B9] The role of oxide grain boundaries in the oxidation of zirconium alloy fuel cladding

^○Maria S Yankova¹, Felicity Baxter^1,2, Alistair Garner¹, Philipp Frankel¹, Christopher P Race¹ (1.Materials Performance Centre, School of Materials, University of Manchester, UK, 2.Corrosion and Materials Science, Wood. PLC, UK)

Oxidation of the Zr alloy fuel cladding in light water reactors is one of the key degradation mechanisms, limiting the amount of fuel burned. The structural and electronic properties of monoclinic and tetragonal zirconia grain boundaries strongly affect the transport of species through the oxide layer. Improving the understanding of oxygen transport through the oxide grain boundaries, and its interaction with dopant point defects, is an important factor in achieving a more mechanistic knowledge and better control of the corrosion process. We are exploiting a combination of density functional theory (DFT) simulation, scanning precession electron diffraction in the transmission electron microscope (SPED-TEM) and novel Python-based texture analysis to obtain an improved mechanistic understanding of the oxide microstructure. We have investigated the effect of oxygen defects and key alloying elements such as Sn and Nb on the structural and electronic properties of representative oxide grain boundaries using DFT. We have investigated dopant-oxygen vacancy binding which can have a significant effect on oxygen conductivty. We have characterised the grain boundary misorientation distribution in non-irradiated and irradiated oxides with estimates on the relative boundary energetics. We have further used the results of our DFT calculations to test a range of empirical potentials for the Zr-O system to establish their suitability for computational modelling of zirconia at microstructural length-scales.