THE EFFECT OF THERMAL TREATMENT ON THE STRUCTURE AND COMPOSITION OF A SOLID SOLUTION OF UC-TAC

摘要

Advanced thermionic fuel elements (TFE's) are being considered to increase the thermal output of thermionic reactors. Materials based on uranium carbide are good candidates for use as a nuclear fuel for these advanced higher thermal output thermionic fuel elements. A nuclear fuel with a composition based on the solid solution of uranium carbide-tantalum carbide (UC-TaC) has several advantages over other uranium carbide based solid solutions. These advantages include low vaporization at elevated temperatures and a higher corrosion resistance in air. Additionally, for fast reactors, UC-TaC fuel has been shown to prevent reactor criticalityif filled with water; an important safety consideration where water submersion of the reactor is a possibility.The objective of this study was to determine the compositional and microstructural stability of porous (U_(0.7)-Ta_(0.3))C_(0.99). Pellets of (U_(0.7)-Ta_(0.3))C_(0.99) were prepared with nominal porosities of 10% and 20% and thermally annealed in vacuum at 1873K and 2073K for 500 hours.The analyses showed that the microstructure was unaffected by the thermal exposures, remaining equiaxed and single phase. Slight variations were observed in the chemical composition of the pellets as measured by x-ray diffraction and chemical analyses.