PNNL

Abstract

Efficient separation of molybdenum from a uranium metal alloy is explored using nitrogen trifluoride. The target was an alloy of 10Wt % molybdenum metal in uranium metal (U-10Mo), which has historical and current importance in the nuclear industry. The reaction of the material with NF3 below 200 ?C is exothermic and can produce critical self-heating in the U-10Mo alloy and consequently compromise good separation of Mo and U. The self-heating behavior was evaluated using thermal gravimetric methods, in which it was found that the separation of Mo from U consistently exceeded 99%. Gas–solid models of the four exothermic steps in the reaction are consistent with nucleation phenomena on the U metal surface that are responsible for (step 1) initiation of the reaction heats and (step 2) rapid rate acceleration. Overall, the results allowed scale-up of the reaction to 20-g with very high decontamination of Mo from uranium with no excursion behavior.