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ORIGINAL RESEARCH article

Front. Nucl. Eng.
Sec. Nuclear Materials
Volume 3 - 2024 | doi: 10.3389/fnuen.2024.1465080
This article is part of the Research Topic Structures and Properties of Fluorite-related Systems for Nuclear Applications View all 3 articles

Insights on the UO2+x/U4O9 phase characterization in oxidized UO2 pellets as a function of the hyper-stoichiometry

Provisionally accepted
Clotilde Gaillard Clotilde Gaillard 1*Hélène Lotz Hélène Lotz 1Lola Sarrasin Lola Sarrasin 1Yves Pipon Yves Pipon 1Roland Ducher Roland Ducher 2Nathalie Moncoffre Nathalie Moncoffre 1
  • 1 UMR5822 - Institut de Physique des 2 Infinis, Villeurbanne, France
  • 2 Institut de Radioprotection et de Sureté nucléaire, Cadarache, Saint Paul Lez Durance, France

The final, formatted version of the article will be published soon.

    We present new insights on the study of the UO2+x/U4O9 equilibrium in UO2 as a function of the hyperstoichiometry x, by coupling HERFD-XANES at the uranium M4-edge and micro-Raman spectroscopy mapping. XANES allowed to measure the uranium speciation in the samples while Raman spectroscopy was used to characterize individually the composition and localization of the different oxide phases. UO2 pellets were oxidized under dry conditions at temperatures above the UO2+x/U4O9 phase transition to reach hyper-stoichiometries in the range 0.01  x  0.1. Combining both technics, we could determine the proportion between U4O9 and UO2+x. We show that at low O/U ratio, U4O9 is present as small clusters inside UO2 grains. As the O/U increases, we evidence the formation of a network of U4O9 crystallized inside UO2+x grains. The variation of the UO2+x phase hyperstoichiometry (x) was evaluated as a function of the sample oxidation.

    Keywords: UO2, Oxidation, U4O9, Raman spectroscopy, HERFD-XANES

    Received: 15 Jul 2024; Accepted: 16 Sep 2024.

    Copyright: © 2024 Gaillard, Lotz, Sarrasin, Pipon, Ducher and Moncoffre. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Clotilde Gaillard, UMR5822 - Institut de Physique des 2 Infinis, Villeurbanne, France

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