Unified Effect of Dispersed Xe on the Thermal Conductivity of UO2 Predicted by Three Interatomic Potentials

WM Chen and XM Bai, JOM, 72, 1710-1718 (2020).

DOI: 10.1007/s11837-019-03985-9

Thermal conductivity is a critical fuel performance property of uranium dioxide (UO2)-based nuclear fuels. Numerous studies have shown that xenon (Xe) fission gas plays a major role in fuel thermal conductivity degradation. It has also been shown that dispersed Xe atoms can cause a stronger phonon-scattering effect than their clustered form. In this work, molecular dynamics simulations are conducted to study the dispersed Xe-induced thermal conductivity reduction using three different interatomic potentials. It is found that although these potentials result in significant discrepancies in the absolute thermal conductivity values, the normalized values are very similar at a wide range of temperatures and Xe concentrations. By integrating this unified effect into the experimentally measured thermal conductivities, a new analytical model is developed to predict the realistic thermal conductivities of UO2 at different dispersed Xe concentrations and temperatures. Using this new model, the critical Xe concentration that offsets the grain boundary Kapitza resistance effect in a high burnup structure is revisited.

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