Development of a mesoscopic particle model for synthesis of uranium-ceramic nuclear fuel

A novel technique has been developed to fabricate uranium-ceramic nuclear fuel using the depleted uranium (DU), U3O8 powder, and allylhydridopolycarbosilane (AHPCS) polymer precursor. This process involves a continuous change of the composition, porosity, and material properties. To fabricate nuclear fuel with a uniform structure/volume ratio, it is important to understand the transport phenomena during high temperature processing and at different length scales. In our prior work, a system-level model based on the reactive porous medium theory was developed to account for pyrolysis process during the uranium-ceramic fuel fabrication. In this paper, a mesoscopic model based on the smoothed particle hydrodynamics (SPH) is developed to simulate the synthesis of filler U3O8 particles and SiC matrix. The system-level model provides the necessary thermal boundary conditions for the mesoscopic simulation. The evolution of the particle concentration and the structure as well as the composition of the composite produced is investigated. Since the process heat flux plays an important role in the material quality and uniformity, the effect of the heating rate, filler particle size and distribution on the uniformity and the structure of the final product are investigated. The uncertainty issue is also discussed.