Monitoring bromide effect on radiolytic yields using in situ observations of uranyl oxide precipitation in the electron microscope

Abstract

During electron microscopy observations of uranium-bearing phases and solutions in a liquid cell, the electron beam induced radiolysis causes changes in the chemistry of the system. This could be useful for investigating accelerated alteration of UO₂ and can be also used to monitor radiolytic effects. Low concentrations of bromide in aqueous solutions are known to reduce the generation rate of H₂O₂ during radiolysis and increase H₂ production. We deduced the presence of radiolytic H₂O₂ by monitoring the formation of a uranyl peroxide solid from both solid UO₂ and a solution of ammonium uranyl carbonate at neutral pH. Additionally, the effect of bromine on water radiolysis was investigated through chemical modelling and in situ electron microscopy. By measuring the contrast in the electron microscopy images it was possible to monitor H₂O₂ formation and diffusion from the irradiated zone in agreement with the models.