The ignition of binary alloys of uranium

Abstract A study is reported of the effect of alloying additions on the ignition of uranium. The experiments were performed by placing nominal 8.5-mm alloy cubes in a flowing oxidizing atmosphere within a furnace whose temperature was increasing at the rate of 10° C/min. Differences in the sample temperaturetime curves were noted for binary uranium alloys containing 0.5, 1 and 2 at % of 24 different elements. Results were interpreted in terms of the effect of the alloying addition on the previously demonstrated transition of the oxide at 400–500° C from an autocatalytic to a protective form. Additions of aluminum in particular and certain other alloys including beryllium, bismuth, carbon, lead, molybdenum, niobium, palladium, platinum, ruthenium, silicon, titanium and vanadium inhibited the oxide transition and thereby lowered the ignition temperature. Another effect produced notably by copper (but also by bismuth, lead, palladium, platinum, ruthenium and vanadium) was an increase in the protectiveness of the oxide formed at temperatures greater than 500° C. Very complex, but reproducible temperaturetime curves were obtained when both effects occurred with the same alloy. Alloying additions of cerium, chromium, hydrogen, iron, nickel, rhodium, silver, tantalum, thorium and zirconium had no significant effect on the ignition behavior of uranium at the low concentration levels studied.