Role of lithium in enhancing radiation tolerance under γ-irradiation in lithium borosilicate waste glasses

Lithium-containing borosilicate glasses are used for the safe containment of high-level nuclear waste in the UK. Glasses were fabricated with varying Li 2 O contents and irradiated to a total γ-dose of 80 MGy to probe the relationship between Li 2 O contents and γ irradiation-induced defects. Semi-quantitative X-band Electron Paramagnetic Resonance (EPR) measurements revealed the formation of boron-oxygen hole centres (BOHC), electron-trap centres, Oxy radicals and hole centres (HC 1 ) defects after γ-radiation. The results highlight the beneficial impact lithium has on the glass network against the formation of paramagnetic defects by transforming BO 3 sites to [BO 4 ] − . Experimental evidence from EPR and Nuclear Magnetic Resonance (NMR) spectroscopy indicated that the primary defects formed in the 4-component and 7-component glasses are BOHCs on bridging oxygens of the BO 3 sites and Oxy radicals linked to silicon atoms, respectively. All glass compositions reached defect saturation around 25 MGy suggesting that the number of components in the glass network or Li 2 O content does not significantly influence saturation dose, however, no change in the environment or connectivity of the boron, sodium or silicon subnetworks was observed by multinuclear NMR.