Chromium doping effects on UO2 grain boundary chemistry: A combined experimental and modeling approach

AJ Terricabras and COT Galvin and M Kosmidou and M Pena and A van Veelen and WD Neilson and SJ Dillon and MWD Cooper and DA Andersson and SC Finkeldei and JT White, JOURNAL OF NUCLEAR MATERIALS, 617, 156114 (2025).

DOI: 10.1016/j.jnucmat.2025.156114

Chromium-doped UO2 has been investigated as an Accident Tolerant Fuel (ATF) concept to enhance the performance and safety of Light Water Reactors (LWR). This study explores the impact of varying Cr doping levels on its segregation to and precipitation at grain boundaries of UO2 through characterization analysis using transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDS). A broad range of Cr doping levels is examined, from low solubility concentrations (750 ppm) to near-maximum solubility levels (2500 ppm) and extending beyond reported solubility limits (7800 ppm). The study compares these doping levels with undoped UO2, evaluating their effects on the atomic concentration of Cr at grain boundaries and grain boundary thickness, all of which are influenced by Cr segregation. Changes in oxidation state were determined via X-ray Absorption Near Edge Structure (XANES). Molecular dynamics simulations are compared to experimental results, discussing concentration evolution, grain boundary type, and segregation energies.

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