Targeted uranium recovery from complex alloys using fluoride volatility

[Display omitted] •Stocks of enriched uranium (EU) in nuclear fuel exist as a variety of alloy types.•Recovery of EU and other fuel constituents is time intensive and fuel-type sensitive.•A unique low temperature reactivity of NF3 on U imparts unusual reactivity to U alloys.•This novel reactivity potentially provides for rapid recovery of EU. A single step separation of molybdenum from a multicomponent uranium alloy, 10 wt.% Mo in uranium metal, (U-10Mo)–Zr is explored using nitrogen trifluoride. The separation takes advantage of an unusually low temperature behavior of NF3. Exposure of the alloy to flowing NF3 between 100–200 °C caused surface area dependent, NF3 concentration, and temperature dependent thermal runaway that threatened the viability of the separation. Gravimetric methods were used to acquire temperature and NF3 concentration dependent profiles to understand the nature of the self-heating and to establish practical conditions for the separation. Scale-up to multigram quantities of the composite is described. In this effort, the use of larger product masses helped to divulge potential metal/MoF6 redox behavior of during the fluorination and acknowledgement of some unexpected chemistries as the metals evolved from the metallic state to their higher fluorides in the presence of what appears to be a catalytic or otherwise activated NF3-uranium metal surface.