Uranium diboride (UB2) has a greater uranium density and a higher thermal conductivity than UO2, both traits that result in increased performance for nuclear fuels. For the first time, UB2 has been prepared via a method suitable for industrial production.
A synthesis procedure suitable for industrial-scale production is a key requirement for any nuclear fuel with commercial ambitions. Being focused on the preparation of small amounts of material for research purposes, the previously-reported synthesis methods for UB2 have always relied on various forms of direct reaction between elemental uranium and boron. While these methods allow to finely control the purity of the final product, they are labour-intensive, have poor robustness and require expensive starting materials.
The carbo/borothermic reduction of uranium dioxide with boron carbide (B4C) and carbon (C) offers a more practical and potentially scalable pathway towards the preparation of UB2.
The research is a joint effort between the Nuclear Futures Institute of Bangor University and the Nuclear Fuel Centre of Excellence of the University of Manchester. Mr. Fabio Martini and Dr. Simon Middleburgh used literature data and Density Functional Theory calculations to build a thermodynamic model of the reaction of formation of UB2, which was then used to devise a procedure for its synthesis. Experimental work was then carried out by researchers at the Nuclear Fuel Centre of Excellence of the University of Manchester. A series of experiments allowed to refine the synthesis method and afforded results in line with the thermodynamic model. 90% pure UB2 was eventually obtained, thereby proving the feasibility of the process. Work is ongoing on further optimization of the procedure.
Further details of the calculations and results may be found in the full publication available online here.
J. Turner, F. Martini, J. Buckley, G. Phillips, S.C. Middleburgh, T.J. Abram, Synthesis of candidate advanced technology fuel: Uranium diboride (UB2) via carbo/borothermic reduction of UO2, Journal of Nuclear Materials, Volume 540, 2020