Hydride-catalyzed corrosion of plutonium by air: Initiation by plutonium monoxide monohydride

Chemistry and kinetics of air reactions with plutonium monoxide monohydride (PuOH) and with mixtures of the oxide hydride and plutonium metal are defined by results of pressure-volume-temperature (PVT) measurements. Test with specimens prepared by total and partial corrosion of plutonium in 0.05 M sodium chloride solution show that reaction of residual water continues to generate H2 after liquid water is removed by evacuation. Rapid exposure of PuOH to air at room temperature does not produce a detectable reaction, but similar exposure of a partially corroded metal sample containing Pu and PuOH results in hydride (PuHx)-catalyzed corrosion of the residual Pu. Kinetics of he first-order reaction resulting in formation of the PuHx catalyst and of the indiscriminate reaction of N2 and O2 with plutonium metal are defined. The rate of the catalyzed Pu+air reaction is independent of temperature (Ea = 0), varies as the square of air pressure, and equals 0.78 ± 0.03 g Pu/cm2 min in air at one atmosphere. The absence of pyrophoric behavior for PuOH and differences in the reactivities of PuOH and PuOH + Pu mixtures are attributed to kinetic control by gaseous reaction products. Thermodynamic properties of the oxide hydride are estimated, particle size distributions of corrosion products are presented, and potential hazards associated with products formed by aqueous corrosion of plutonium are discussed