The Kinetics of the Hydriding of Uranium Metal

The reaction of massive uranium metal with hydrogen gas was studied using ultra-high vacuum, automated gas buret techniques, and linear rate data for this reaction are reported over a wide range of temperature (--10-250 deg C) and pressure (10 mPa-1 MPa). The rate followed a half-power pressure dependence in the mid-range of pressures studied and was truncated at the limits of high and low pressures, and high temperatures. The hydriding rates are compared with data and calculations based on various models. One model, which qualitatively describes all the features of these data, is discussed in terms of how components contributing to the model can be adjusted to achieve a complete description of the data. At 21 deg C, reversible H sorption on the UH sub 3 reaction product was detected from kinetic effects associated with restarting the hydriding process in the presence of the UH sub 3 reaction product, and was shown to occur on pure UH sub 3 in monolayer quantities. The relative yields of the alpha and beta phases of UH sub 3 were shown to be a function of the hydriding rate, with slower rates favoring beta -UH sub 3 formation. Graphs. 9 ref.--AA