Effect of particle density on powder mixing in nuclear fuel pellet fabrication using discrete element method

Abstract

Granular mixing is a fundamental operation in the fabrication of mixed-oxide (MOX) nuclear fuels, where achieving homogeneous blends of constituent materials is essential for reactor performance and safety. Using particle dynamics simulations, we investigate the flow behavior and binary mixing of equi-sized spherical particles with differing densities in horizontal rotating drums operating within the cascading regime. An extensive parametric study is conducted by systematically varying the particle density while keeping all other particle properties fixed. The simulation results indicate that mixtures composed of particles with similar densities undergo efficient mixing, whereas mixtures with large density contrasts exhibit persistent segregation. In the latter case, denser particles are concentrated near the drum core, while lighter particles settle away from the core. Additionally, the curvature of the free surface is observed to increase monotonically with the particle density ratio, indicating a strong coupling between density-driven segregation and surface flow dynamics. These findings provide insights into the mechanisms governing density segregation in rotating drums and have implications for optimizing mixing processes in industrial and nuclear fuel fabrications contexts.