Potential nuclear fuels in the US-UC-UC2 system

A solid-solution study of the US-UC-UC₂ system at 1760 and 2170 K has revealed the range of compositions yielding the mandatory single-phase solid solutions for consideration as potential nuclear fuels. Two such compositions containing 20 and 40 mol%, respectively, of dissolved carbides have been selected, and convenient methods are described for their preparation from stoichiometric UC, ZnS and U₃O₈. Many of the physical and chemical properties of these compositions either as powders or as sintered pellets are reported. Compatibility with stainless steels under the test conditions is extremely good. However, sodium bonding is precluded through chemical reactions leading to the formation of Na₂S, and ultimately free uranium. Creep strengths are greater than for hyperstoichiometric UC. It is concluded that the 80 mol% US composition with less than 10 mol% UC₂is promising as a potential nuclear fuel, the 60 mol% US material being less so.