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International audience; Thanks to its precision, its reproducibility and its stability, Electron Microprobe is a well suited technique for accurately analyzing nearly all chemical elements at concentration levels down to few 10’s ppm with a spatial resolution of about 1 µm, which is relevant to microstructures in a wide variety of materials and mineral specimens. For irradiated samples, EPMA is also one of the technique of choices and can support nuclear fuel development, control, metallurgical or glass analysis. It reveals fine compositional details and the distribution of main and trace elements across the surface of the sample.CAMECA leader in scientific instruments has been manufacturing Electron Microprobe (EPMA) since 1958 and will present its latest CAMECA shielded EPMA model, SKAPHIA released in 2016 for hotlab facilities. One example of the LECA/STAR shielded EPMA in hotlab handling nuclear fuel will be highlighted. In this example, the microstructure and chemical evolution of fuel pellets submitted to two different nuclear severe accident scenarii are shown. EPMA helped to highlight the impact of the atmosphere (i.e the oxygen potential) on the behavior of the fuel and fission products during these tests. These studies are of particular importance to evaluate and better predict the consequences of such an accident in term of contamination.

National audience; Présentation de la microsonde du Leca-star lors de la première journée utilisateur de SX (organise par cameca)

International audience; This work is concerned with the experimental validation of a constitutive model developed at the “Commissariat à l'Energie Atomique” to simulate radioactive bituminized waste leaching. In this aim, two types of experimental studies have been performed. First, the porosity created by water in leached bituminized waste samples has been observed thanks to an Environmental scanning electron microscope (ESEM) and quantified by standard image analysis techniques. Second, the diffusion coefficient of water in leached bituminized waste samples, a key parameter with respect to leaching kinetics, has been measured experimentally. The correlation between model-based results and experimental data on porosity profiles and water diffusion coefficients confirms to a certain extent the validity of the proposed mathematical description.; Ce travail a eu pour objectif de tester expérimentalement la robustesse du modèle développé au Commissariat à l'énergie atomique pour simuler l'altération par l'eau des déchets nucléaires bitumés. Dans cette optique, deux types d'expériences ont été entreprises. Dans un premier temps, la structure poreuse d'enrobés bitumes altérés par l'eau a été observée à l'aide d'un microscope électronique à balayage environnemental (MEB environnemental) et quantifiée par une méthode d'analyse d'images. Dans un second temps, le coefficient de diffusion de l'eau dans des enrobés bitumes lixiviés, paramètre clé de l'altération, a été mesuré expérimentalement. La bonne concordance entre la modélisation et les données expérimentales concernant la structure interne des enrobés altérés a permis de conforter la description mathématique des phénomènes proposée.Abstract