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European Commission

Short description of the work
We have performed X-Ray Absoprtion Near Edge Structure (XANES) Studies on the sodium uranates Na3UO4, Na4UO5 and Na2U2O7 at the Rossendorf Beamline (ROBL, ESRF, Grenoble) under the Talisman framework. We have established the local structure and charge distribution of the uranium cation in those compounds. Na4UO5 and Na2U2O7 present uranium in the oxidation state (VI). In the case of the Na3UO4 compound however, XANES spectra have revealed uranium (VI) and not uranium (V) as expected. This has led us to revisit the compound’s structure and chemical composition, namely Na3.2U0.8O4, by incorporation of 20% excess sodium on the uranium site. Those results have direct consequences from thermodynamics’ perspectives for the fuel-sodium interaction.

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