J. Phys. IV France
Volume 118, November 2004
Page(s) 127 - 134

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 250$^{\circ}$C

G. Rousseau1, 2, 3, L. Desgranges1, J.C. Nièpce2, G. Baldinozzi3 and J.F. Bérar4

1  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

The structural evolution of UO2 during its oxidation into U3O8 at 250$^{\circ}$C 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 $\alpha$ -U3O7 tetragonal phase ( ${\rm c}/{\rm a}\,{<}\,1$) 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