Spectroscopic determination of heterogeneities in uranyl-doped glasses

Fluorescence spectroscopic methods were used to obtain information concerning the speciation of uranyl doped into three types of glass: a silica sol-gel glass, a frit glass (a simulant glass for vitrification of radionuclides), and a pyrex glass. Fluorescence decay curves were acquired and lifetime distributions were calculated for each glass via a continuous model analysis program. The uranyl ion contained in the commercial borosilicate glass shows a single lifetime at approximately 370 μs, while the other glasses show multiple peaks at various lifetimes. In addition, a red shift in the emission spectrum of the uranyl ion in the frit and commercial glass indicates stronger bonding of the ion in these glasses as compared to the sol-gel glass. It is concluded that the commercial borosilicate glass provides the most homogeneous environment for the uranyl ion while phase separation in the frit is responsible for the observed multicomponent lifetime distribution.