On the origin of the sigmoid shape in the UO2 oxidation weight gain curvesReport as inadecuate

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1 LLCC - Laboratoire des Lois de Comportement du Combustible 2 LPMG-EMSE - Laboratoire des Procédés en Milieux Granulaires 3 SPIN-ENSMSE - Centre Sciences des Processus Industriels et Naturels 4 ProcESS-ENSMSE - Département Procédés et évolution des systèmes avec solides 5 SPMS - Laboratoire Structures, Propriétés et Modélisation des solides 6 LICB - Laboratoire Interdisciplinaire Carnot de Bourgogne 7 L3MR - Laboratoire de Mesures et Modélisation de la Migration des Radionucléides DPC - Département de Physico-Chimie : DEN-DPC

Abstract : Cracking and spalling are known to occur during the oxidation of UO2. However, these phenomena are not considered by the existing kinetic models of the oxidation of UO2 into U3O8. In this study the oxidation of UO2 samples of various sizes from the single crystal to nanopowders, has been followed by isothermal and isobaric thermogravimetry, environmental scanning electron microscopy and in situ X-ray diffraction at temperatures ranging from 250 to 370°C in air. It has been shown that cracking occurs once a critical layer thickness of intermediate oxide has been reached, which corresponds to the beginning of the sigmoid kinetic curve. Cracking contribution to the sigmoid kinetic curve is then discussed as a function of temperature, and on the basis of nucleation and growth processes.

Keywords : UO2 Nuclear applications Electron microscopy X-ray methods

Author: Ludovic Quémard - Lionel Desgranges - Vincent Bouineau - Michèle Pijolat - G. Baldinozzi - Nadine Millot - Jean-Claude Nièpce

Source: https://hal.archives-ouvertes.fr/


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