In vitrification process of HLW in Japan, Joule heating method is adopted. In this method, the electrical conductivity of glass melts affects melting temperature and other properties such as viscosity. In addition, the high-temperature viscosity affects the convection in the furnace and the flow rate into the stainless canister. Therefore, it is important to obtain basic data on the high-temperature properties of melts for the advancement and optimization of the vitrification process. In this study, we investigated the effects of the glass composition and the HLW contents on the viscosity and electrical conductivity of SiO2-B2O3-Al2O3-Na2O-Li2O-CaO-ZnO.

The glass composition was classified by composition parameters K [SiO2/B2O3], K’ [SiO2/(B2O3+Al2O3)], R’’ [(Na2O+Li2O+CaO)/ (B2O3+Al2O3)]. The viscosity of glass melts was measured by rotating crucible viscometer from 1223K to 1673K. And the electrical conductivity of glass melts was measured by adapting four-probe method from 1273K to 1673K. Both measurements were performed at intervals of 50K at a cooling rate of 5K/min from the maximum temperature.

Fig.1 shows the temperature dependences of the logarithm of viscosity (logη) and electrical conductivity (logκ) of the SiO2-B2O3-Al2O3-Na2O-Li2O-CaO-ZnO glasses. In all samples, both of logηand logκ were found to show linear relationships with reciprocal temperature (1/T) and to follow the Arrhenius equation. Then, the viscosity of glass melts is increased with increasing K and K’. On the other hand, the viscosity of glass melts is decreased with increasing R’’.
The electrical conductivity of glass melts is decreased with increasing K and K’ and increased with decreasing with R’’. The results are explained in terms of cation-oxygen interactions of component oxides.

This work was carried out as a part of the basic research programs of vitrification technology for waste volume reduction（JPJ010599）supported by the Ministry of Economy, Trade and Industry, Japan.