PNNL

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 can be useful for investigating accelerated alteration of UO2 and can be also used to monitor radiolytic events themselves. 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 UO2 and ammonium uranyl carbonate solution at neutral pH. Additionally, the role 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.