REDUCTION OF UO2+X BY ATOMIC-HYDROGEN

The modulated molecular beam technique with in situ mass spectrometric phase sensitive detection was used to study the kinetics of atomic hydrogen reduction of hyperstoichiometric uranium dioxide. The atomic hydrogen portion of an incident mixed-collisionless H/H2 beam chemisorbed onto urania surface with a sticking probability of 0.7 ± 0.1. A major fraction of the chemisorbed H atom recombined to produce H2 gas, and only a small fraction entered the parallel channel leading to water production. Both the recombination and the water production processes were linear with respect to the incident H-atom beam intensity. The recombination step was rapid, but a slow desorption-like step controlled the kinetics of water production. A phenomenological model was fitted to the data. © 1990 American Chemical Society.