A Raman spectroscopy study of bicarbonate effects on UO_2+x

Direct disposal of spent nuclear fuel in underground repositories stable geological formations is an alternative option for the reprocessing Japan. Upon breakdown barriers between waste storage containers and environment a deep repository, release radioactive nuclei from into will occur via groundwater. The be dependent on dissolution rate at fuel/groundwater interface. surface UO2 oxidized form UO2+x, extent hyper-stoichiometry has implications U dissolution. A key component typical groundwater bicarbonate which can range concentration depending repository location. Therefore, to understand effect UO2+x surface, pellets were immersed solution 298 days, oxide was analysed by Raman spectroscopy. Detailed peak analysis spectra showed increased defects after immersion attributed preferential UV/VI UO2+x. Differences defect with without change speciation (U(OH)4 UO2(CO3)34-) as determined calculations. depth profiles constant value x through surface.