Abstract:The adsorption isotherms of CO, CO2 and O2 on UO2 powder at 288 K were measured using static volumetric method, and their effects on the induction time for uranium-hydrogen reaction were investigated by measuring pressure drop combined with in-situ micrographic observation. The Langmuir and Freundlich equations were found to describe well the adsorption behavior of CO and CO2 on UO2, respectively, with the adsorption strength following the ordering of O2>CO2>CO. The effects of oxygen-containing gases on the induction time are closely related to their adsorption properties, and their inhibition efficiency follows the ordering of CO2>CO>O2. The induction time is almost direct proportion to CO or O2 concentration, whereas it varies differently as CO2 concentration depends on its concentration region. The inhibition mechanism of CO or CO2 is mainly attributed to their preferred occupation of active adsorption sites on the uranium surface, whereas that of O2 is relatively complex, which may be related to two surface chemical processes: the formation of water precursor state and the diffusion of adsorbed O particles. The derived model based on the inhibition mechanism and gas adsorption property describes well the influence behavior of CO and CO2 on the induction time.