Fabrication of homogenous pellets by freeze granulation of optimized TiO2-Y2O3 suspensions
F. La Lumia, L. Ramond, C. Pagnoux, G. Bernard-Granger
MOX fuels are used in nuclear reactors. To ensure the manufacture of MOX, wet processes are investigated. Freeze granulation of water-based powder suspension seems a promising way to yield homogenous and easy-to-press UO2-PuO2 granules. These granules are expected to form dense and homogenous pellets by uniaxial pressing. Granules and pellet properties are affected by suspension formulation and atomization conditions. Therefore, these conditions must be studied and optimized to produce granules with good processability and thus MOX pellets with compliant density, homogeneity and absence of defects. In this scope, key properties of water-based suspensions of UO2 and PuO2 surrogate powders, TiO2 and Y2O3 respectively, were firstly studied to assess their suitability for the freeze granulation process. These properties were compared to those of UO2 and PuO2 suspensions to verify and confirm the correctness in the choice of surrogate powders. Then, the freeze granulation process itself was investigated focusing on TiO2-Y2O3 suspensions.
Suspension, Granulation, Freeze drying, UO2, PuO2