Abstract
X-ray absorption spectroscopy is employed to study the local structure of pure and Cr-doped UO2 at 300 K. The U L3-edge EXAFS spectrum is interpreted within the multiplescattering (MS) theory using the results of the classical and ab initio molecular dynamics simulations, allowing us to validate the accuracy of theoretical models. The Cr K-edge XANES is simulated within the full-multiple-scattering formalism considering a substitutional model (Cr at U site). It is shown that both unrelaxed and relaxed structures, produced by ab initio density functional theory (DFT) calculations, fail to describe the experiment.
Highlights
Uranium dioxide (UO2) is employed as a fuel material in most nuclear reactors world-wide
The cubic face centered structure of UO2 provides enough space to accommodate interstitial Cr3+ ions. We address this problem using EXAFS spectroscopy, which is well suited for the local structure investigations of UO2 fuel matrix and Cr dopant
The experimental U L3-edge EXAFS spectra of UO2 were interpreted up to 6 ̊A in R-space using the results of both CMD and AIMD simulations taking into account the MS effects
Summary
Uranium dioxide (UO2) is employed as a fuel material in most nuclear reactors world-wide. We address this problem using EXAFS spectroscopy, which is well suited for the local structure investigations (e.g. first neighbour bond distances and coordination numbers) of UO2 fuel matrix and Cr dopant. The atomic structure around the chromium impurity is relaxed, and the resulting structures are used to calculate the Cr K-edge X-ray absorption near edge (XANES) spectra within the ab initio full-multiple-scattering (FMS) formalism [7].
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