Grain growth and Mo homogenization in U-7Mo atomized particles
Résumé
To enhance the behavior of U-Mo based fuel plates under irradiation, it is currently proposed to optimize the microstructure of U-Mo fresh particles. These optimizations are twofold (grain coarsening and intragranular Mo homogenization). In this paper, further insights into the intrinsic kinetics of both mechanisms during thermal annealing are given. U-7Mo grain growth in atomized particles was investigated ex situ using Electron Backscattered Electron Diffraction (EBSD) [1]. Samples were selected from the EMPIrE and the KOMO-5 tests. It was found that EMPIrE annealing conditions (1000C during 1 hour) led to a significant grain growth (up to 33-35 µm) in good agreement with predictive modeling performed by ANL [2]. The initial U-7Mo grain size was 2-3 µm. Mo homogenization was followed in situ using neutron diffraction. Two sets of atomized U-7Mo powder were annealed under different conditions but up to comparable homogenization levels. Mo homogenization kinetics were derived. At the end of these treatments, both homogenized U-7Mo powders were tested at 450C i.e. to emulate fuel plate manufacturing conditions.
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