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Etude des phases solides métastable et stable de corium issus de trempe par approche multiechelle, étude d'un chemin réactionnel

Abstract : Knowledge of the solid state of the prototypical corium resulting from ternary oxide systems of the UZrO type simulating the melting of the reactor core, is fundamental both from the point of view of the understanding of the progression of the severe accident and the dismantling of the Fukushima reactors. It is a material formed far from thermodynamic equilibrium by the thermal fusion of the nuclear fuel and the interaction with the zircaloy cladding at high temperature (T > 2800K). It has a large solid solution of uranium and zirconium oxide that crystallizes in a cubic structure of space group Fm3̅m. Corium formation and chemical composition are strongly influenced by the solidification process and cooling rate. Depending on the severe accident scenario, different phenomena may occur, such as fuel-coolant interaction (FCI). A thorough understanding of the influence of cooling conditions and ICE on the structure and microstructure of prototypical solid coriums requires the use of several experimental approaches. FCI induces a priori the formation of non-equilibrium phase within U1-xZrxO2±y crystals. With the help of studies combining, at different scales, several experimental methods using laboratory equipment (XRD, SEM-EBSD and X-ray microanalysis), and instruments located around synchrotron radiation sources (SOLEIL or ESRF) or the ILL neutron source, we have been able to quantitatively analyze these fluctuations of the cationic composition which are strongly linked to the cooling rate.
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Submitted on : Wednesday, September 7, 2022 - 3:52:52 PM
Last modification on : Tuesday, September 27, 2022 - 4:21:20 AM

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Mohamed Jizzini. Etude des phases solides métastable et stable de corium issus de trempe par approche multiechelle, étude d'un chemin réactionnel. Autre. Université de Limoges, 2022. Français. ⟨NNT : 2022LIMO0060⟩. ⟨tel-03771731⟩

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