The effect of uranium oxide additions on the structure of alkali borosilicate glasses

The effect of uranium on glass structure is of interest in the context both of geological and nuclear waste glasses. In this study, solid state Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy was used to establish the effect of UO3 on the bulk structure of mixed alkali borosilicate glass. The effects of increasing UO3 content on boron co-ordination, alkali co-ordination and network polymerisation, determined using MAS-NMR, show that UO3 acts essentially as an intermediate within the glass, occupying sites in the interstices of the glass network related to the alkali channels. This requires little structural rearrangement of the glass and so allows for the high solubility of UO3. It is shown that each mole of UO3 requires 2 moles of alkali for charge balance. 7Li MAS-NMR spectra indicate that with the addition of UO3 the structural role of Li changes.