The synthesis and air oxidation behavior of U-Si-Al and USi- B compositions

Uranium silicide intermetallic compounds are currently under investigation by the DOE-NE Advanced Fuels Campaign as candidate accident tolerant nuclear fuel concepts. While many U-Si compounds offer benefits compared to reference UO₂ in terms of heavy metal density and thermal conductivity, they have been shown to display poor resistance to oxidizing atmospheres above 400 °C. While light water reactor fuel (LWR) will not be exposed to such oxidizing conditions during normal operation, the stability of candidate LWR fuels to these conditions is important to understand as they may be encountered during certain accident scenarios as well as used fuel storage. The general oxidation behavior of all U-Si compounds is oxidation of uranium; formation of UO₂ followed by U₃O₈ leads to rapid pulverization of the material. It is hypothesized that introducing an additional compositional degree of freedom by exploring U-Si-X (X=Al or B) ternary systems may provide the means to design a candidate nuclear fuel which optimizes the benefits of each binary. Reported here are the fuel synthesis techniques and metallurgical processing of U-Si-Al and U-Si-B ternaries, and the oxidation results of the ternary compounds will be presented in comparison with the traditional U-Si fuel compounds.