Étude du comportement mécanique d’UO2 implanté en helium par micro-diffraction des rayons X et modélisation par éléments finis

Abstract : In order to study the mechanical behavior of nuclear fuel during direct long term storage, UO2 polycrystals were implanted with Helium ions at a thin surface layer (1 µm approximately), which leads to stress and strain fields in the layer. Strains were measured, at the grains scale, by X-ray micro-diffraction, using synchrotron radiation (ESRF). Image analysis methods were developed for an automatic analysis of the large number of diffraction patterns. Applying statistical tools to Laue patterns allows an automatic detection of low quality images, and enhances the measurement precision. At low layer thickness, the mechanical interaction between grains can be neglected. At higher thickness, experimental results showed a higher mechanical interaction near grain boundaries that can be modeled using finite elements method. Geostatistical tools were used to quantify these interactions. The swelling and the elastic constants in the implanted layer can be estimated through the measured strains on a large number of grains with different orientations. This work allows the determination of the swelling of nuclear fuel in irradiation conditions, as well as the modification of its elastic properties
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Marcelle Ibrahim. Étude du comportement mécanique d’UO2 implanté en helium par micro-diffraction des rayons X et modélisation par éléments finis. Matériaux. Université Paris-Est, 2015. Français. ⟨NNT : 2015PESC1140⟩. ⟨tel-01305585⟩

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