The effect of Cs2O additions on HLW wasteform glasses

Abstract Physical parameters and structural characteristics are reported for the mixed alkali borosilicate glass system, x Cs 2 O(100 − x )(MW) (0 ⩽ x ⩽ 9.66) where MW is the BNFL wasteform glass (10.29 mol% Li 2 O, 10.53 mol% Na 2 O, 18.57 mol% B 2 O 3 , 60.61 mol% SiO 2 ). Glass density was found to increase with x whilst the glass transition temperature ( T g ) decreased. The fraction of four-coordinated boron (N 4 ) determined from 11 B magic angle spinning nuclear magnetic resonance (MAS NMR) increased with x in a manner consistent with previous reports on the sodium–lithium–borosilicate system and contrary to the Dell model. 29 Si MAS NMR was used to identify the fraction of Q 4 (B) and Q 3 units as a function of x . Raman spectra indicated the presence of reedmergnerite and danburite superstructural units. Mass loss measurements showed a non-linear variation with x , having a maximum between 7 and 8 mol% Cs 2 O and a correlation was found between the amount of Q 3 units in the solid and the volatilization loss from the melt.