6533b82cfe1ef96bd128f36d

RESEARCH PRODUCT

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

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The structural evolution of UO 2 during its oxidation into U 3 O 8 at 250°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 α-U 3 O 7 tetragonal phase (c/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 UO, and U 4 O 9 exist simultaneously, confirms the wrong phase attribution in the literature.