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Direct measurements of the rate constant for the bimolecular reaction OH + H2 -H + H20 have been completed in the temperature range 800-1550 K. In these experiments, small amounts of water vapor were photolyzed with an excimer laser to 'instantaneously" create OH radicals and H atoms. The subsequent time history of the OH radicals was monitored by using laser-induced fluorescence. Analysis of the OH removal rate as a function of added hydrogen yielded the rate constant for the above reaction. The temperature range of our measurements bridges the gap between the recent shock tube data (1246-2581 K) of Michael and Sutherland; Frank and Just; Davidson, Chang, and Hanson and the quartz cell flash photolysis data (250-1050 K) of Tully, Ravishankara, and co-workers. Our data are in very good agreement with these previous data sets in the overlap region. By combining our data with these four data sets, we derive a new rate constant expression, k = (3.56 X 10-16)T1,52 exp[-l736/7'l cm3 molecule-' s-I, that is applicable in the temperature range 250-2581 K.

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Alkaline hydrolysis is used to convert high explosives to nonenergetic, aqueous compounds. Base hydrolysis of high explosives is exothermic (∆H RXN ) 2.3 kJ/g), and thermal runaway of the reaction is a possibility at elevated temperatures (>120 °C) where the rate of reaction is large. Thermal runaway could result in an accidental detonation of the energetic material being treated, so safe operating parameters for base hydrolysis need to be determined. To measure the safe operating temperature, base hydrolysis was performed at temperatures ramped from 20 to 300 °C. The results show that PBX 9501 molding powder detonates at a 185 °C bulk temperature in 1.5 M NaOH with a 4.5 °C/min linear temperature ramp and no agitation. The reaction of pressed PBX 9501 with 0.75, 1.5, and 3.0 M NaOH and water and both pressed and nonpressed PBX 9404 with 0.75, 1.5 M, and 3.0 M NaOH and water did not produce a detonation with a 4.5 °C/min linear temperature ramp. A previously developed reaction rate model was used to show that thermal runaway should occur when the base hydrolysis reaction rate reached a maximum at a bulk temperature between 185 and 225 °C.