J. Phys. IV France 118 (2004) 127-134
DOI: 10.1051/jp4:2004118015

Contribution of the synchrotron diffraction study of the oxidation of uranium dioxide at 250C

G. Rousseau^{1, 2, 3}, L. Desgranges¹, J.C. Nièpce², G. Baldinozzi³ and J.F. Bérar<sup>4

1</sup>  CEA Cadarache, DEC/S3C/LECMI Bât. 316, 13108 St. Paul-lez-Durance, France
²  LRRS, UMR 5613 CNRS-Université de Bourgogne, 9 Av. Alain Savary BP. 47870, 21078 Dijon, France
³  SPMS, UMR 8580 CNRS-École Centrale Paris, Grande voie des vignes, 92295 Châtenay-Malabry, France
⁴  D2AM CRG, CNRS, ESRF - Polygone Scientifique Louis Néel, 6 rue Jules Horowitz, 38000 Grenoble, France

Abstract
The structural evolution of UO₂ during its oxidation into U₃O₈ at 250C in air was studied by in-situ synchrotron X-ray diffraction on the D2AM-CRG beamline at ESRF. The aim of this study is to determine the phases which are likely to appear during a long term storage of used nuclear fuel. Our results are in disagreement with the literature where the existence of the secondary cubic phase is not reported, and an -U₃O₇ tetragonal phase ( ) is also mentioned but definitely not observed. These previous interpretations are possibly due to a poor instrumental resolution, inducing a sensible broadening of the diffraction peaks. Particularly, the fact that the instrumental resolution was unable to resolve the splitting of the 111 diffraction peak, when UO₂ and U₄O₉ exist simultaneously, confirms the wrong phase attribution in the literature.

© EDP Sciences 2004