The Role of surface-bound hydroxyl radicals in the reaction between HO and UO

Fidalgo, A. B.*; Kumagai, Yuta   ; Jonsson, M.*

In this work, we have studied the reaction between HO and UO with particular focus on the nature of the hydroxyl radical formed as an intermediate. Experiments were performed to study the kinetics of the reaction at different initial HO concentrations. The results show that the consumption rates at a given HO concentration are different depending on the initial HO concentration. This is attributed to an alteration of the reactive interface, likely caused by blocking of surface sites by oxidized U/surface-bound hydroxyl radicals. The U dissolution yield decreases with increasing initial HO concentration. This is expected from the mechanism of catalytic decomposition of HO on oxide surfaces. As the experiments were performed in solutions containing 10 mM and a strong concentration dependence was observed in the 0.2 - 2.0 mM HO concentration range, we conclude that the intermediate hydroxyl radical is surface bound rather than free.