The interaction of molten-lithium droplets with water is studied experimentally. In one set of experiments, droplets of approximately 10- to 15-mm diameter are injected into a vessel filled with water. The reaction is filmed, and pressure measurements are made. The initial metal and water temperatures range from 200 to 500-degrees-C and 20 to 70-degrees-C, respectively. It is found that when reactant temperatures are high, an explosive reaction often occurs. When the initial lithium temperature is >400-degrees-C and the water is >30-degrees-C, the explosive reactions become much more probable, with pressure peaks as high as 4 MPa. The reaction is modeled to explain the temperature threshold for this metal-ignition phenomena. Results with the model support the hypothesis that explosive reactions occur when the lithium droplet surface reaches its saturation temperature while the hydrogen film surrounding the drop is relatively thin. A second set of experiments measures the reaction rate of nonexplosive lithium- water reactions. The test geometry parallels that of the previous experiments, and the reactant temperature combinations are deliberately kept below the observed ignition threshold. Two separate methods are used to determine the reaction rate in each test: One uses a three-color pyrometer to measure the drop temperature as the lithium rises through the water, while the other consists of a photographic technique that measures the amount of hydrogen generated. Measured reaction rates range from approximately 10 to 50 mol/s.m2 with good agreement between the two measurement techniques. The data do not show any significant variation in the reaction rate as a function of either the initial water or initial lithium temperature.
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