Production and Characterization of ZrC-UC Inert Matrix Composite Fuel for Gas Fast Reactors

Abstract

Dispersed fuel composites consisting of uranium carbide particles (microspheres) in a zirconium carbide (inert) matrix were fabricated and characterized. Advanced fuels including refractory inert matrix fuels are being considered for gas fast reactors, which can accommodate a variety of feed materials including recycled transuranics that include minor actinides for incineration and high-level waste reduction. The particles for this effort were fabricated by employing a custom built rotating electrode machine. This process employed a uranium carbide electrode manufactured by combustion synthesis of uranium hydride and graphite powders. Two process parameters, namely, arc intensity and rotational speed, were varied to assess their effects on the size of the particles produced. The particles were characterized for microstructure, density, and composition (homogeneity). These particles were mixed with pure zirconium and graphite powders in different matrix to particle volumetric ratios of 90/10, 80/20, and 70/30 and inductively heated to 1850°C to initiate combustion synthesis to produce composites of zirconium carbide with the embedded uranium carbide particles. The aim was to limit process temperature and in particular process time, bearing in mind the possible future extensions of these processes to minor actinide-bearing fuels and also to avoid any changes in the structural integrity of the particles and large-scale diffusion of uranium into the matrix. The composites were characterized for microstructure, phase composition, density, and porosity distribution. The results are presented.