Plutonium hydride, sesquioxide and monoxide monohydride: pyrophoricity and catalysis of plutonium corrosion

Reaction rates of air and oxygen with cubic plutonium hydride (PuHx, 1.9<x<3), monoxide monohydride (PuOH), and Pu metal coated with these compounds are described. along with kinetic results for the Pu+H-2 reaction, Pyrophoric tendencies are not observed for PuOH, but exposure of PuHx and PuHx- (or PuOH-) coated Pu to air or O-2 at room temperature result in spontaneous reactions that consume both O-2 and N-2. These reactions and hydriding have zero or slightly negative activation energies and pressure-dependent rates. Pyrophoric reaction of PuHx and PuHx-catalyzed corrosion of Pu depend an thermal maintenance of catalytic Pu2O3 at the gas-solid interface and are prevented by formation of a protective PuO2 layer at low temperatures and law O-2 pressures. The Pu+H-2, reaction is catalyzed by Pu2O3 and PuHx is produced by the Pu+H2O reaction only at conditions where Pu2O3 formation is kinetically favored. Thermal ignition of Pu near 500 degreesC is attributed to autoreduction of the PuO2 surface to Pu2O3 at that temperature. At normal storage temperatures, formation of pyrophoric corrosion products is unlikely in open oxidant-rich systems, but surfaces that catalyze rapid Pu corrosion in air are formed during extended storage in closed systems. (C) 2001 Elsevier Science B.V. All lights reserved.