Study of the crystal field strength in MxUyOz compounds by resonant inelastic X-ray scattering

We propose to investigate the crystal field strength in uranates by means of high-energy-resolution fluorescence detected X-ray absorption spectroscopy at the U L3-edge. The substantial gain in resolution achieved by collecting the Lb5 emission line with the ROBL emission spectrometer, very detailed uranium electronic structure will be obtained as a function of the ligand nature and the U surrounding geometry. Experimental spectra, interpreted using state of the art Density Functional Theory calculations, will provide a complete assessment on the electronic structure of uranium. Moreover, the uranium bonding nature will be tackled by direct evaluation of the crystal field, which represent a key parameter of accurate and predictive theoretical model in 5f chemistry. Finally, the expected data will contribute to improve safety and efficiency of nuclear fuel, especially in case of accident, as Ba is an abundant fission products and Na is the coolant for the future Sodium Fast Reactors.