A detailed description of the reaction mechanisms provides insights into the PuO continuously oxidized by water in the gas-phase. Two reaction pathways were located, isomerization and dehydrogenation, and the corresponding different products are closely examined. Our results indicated that it is difficult to oxidize PuO with a water molecule at room temperature. In the early stages of reaction, the reaction rate constants of the first O–H bond dissociation are very small. Once the dissociations of the O–H bonds were complete, the remaining process will be exothermic, and the best thermochemical conditions observed at dehydrogenation around 42.3 kcal mol−1. Minimum energy crossing points between the septuplet–quintet and septuplet–triplet PESs were searched. Electron localization function and atoms in molecules were performed to analyze the topological property of bonding evolution along the reactions. Rate constants were calculated between 298 and 1000 K by using variational transition-state theory including one-dimensional tunneling effects.
