Formation of high purity uranium via laser induced thermal decomposition of uranium nitride

Producing gram quantities of uranium metal in a controlled manner by traditional methods is challenging due to the complex chemistry of precursor material and extreme thermal requirements. In this article, a novel approach is reported that combines modeling and an advanced experimental technique for extracting uranium from a uranium-containing compound. Using uranium nitride as an example, a computational thermodynamic approach identified a decomposition pathway to convert uranium nitride to uranium metal at temperatures exceeding 2500 K under conditions of rapid material cooling. To realize these extreme conditions, laser-induced heating, which enables fine control of process location and rapid cooling, was utilized for high-temperature modification of material. Uranium nitride was irradiated by a controlled laser under several gaseous conditions including high-vacuum, argon, and nitrogen environments, resulting in uranium metal at yields up to 96%. The complete decomposition leading to pure uranium metal occurs at the high temperature surface region, where laser-based heating induces a surface depression and molten pool of material. The observed kinetic phase behaviors in this study fundamentally differ from previous uranium decomposition studies where small uranium metal precipitates from the nitride bulk are formed at the surface of uranium nitride. (C) 2020 The Authors. Published by Elsevier Ltd.