Stabilization of Uranium Nitride by Aluminum and Chromium Doping

Abstract

Uranium nitride is a promising accident tolerant fuel (ATF) candidate as it has great uranium density and thermal conductivity. The main downside is its inherent weakness to oxidation in mainly water and steam. In this work, uranium nitride was synthesized with 20% of total molar metal content as varying amounts of aluminum and chromium. The material was investigated in terms of oxidation performance and microstructure in order to asses the suitability of said dopants as an approach of stabilization. The material was synthesized as microspheres via the internal sol-gel process and carbothermal reduction at 1550 °C. Aluminum caused a change in microstructure and made the material more porous, which was believed to be the main reason why aluminum reduced oxidation performance during thermogravimetric analysis. This change was attributed to the tendency of aluminum to collect along the grain boundaries, potentially weakening grain adhesion. Only when chromium alone was added the oxidation temperature was increased. Added chromium not only caused caused cracking due to the release of gasses, but also surface formations due to the limited solubility of chromium in uranium nitride.