Electrical properties of borosilicate glasses melted by cold crucible induction melter (CCIM) technology

Reference Presenter Authors
10-011 Dylan Jouglard Jouglard, D.(Commissariat à l'énergie atomique et aux énergies alternatives); Neyret, M.(Commissariat à l'énergie atomique et aux énergies alternatives); Malki, M.(Conditions Extrêmes et Matériaux : Haute Température & Irradiation); Del Campo, L.(Conditions Extrêmes et Matériaux : Haute Température & Irradiation); The CCIM technology used for nuclear waste vitrification is based on an alternating electromagnetic field which allows glass melting due to electrical currents. An isolating coat, called self-crucible, is created onto the water-cooled walls of the crucible and protects them from high temperature effects, corrosion and high electric potential differences. In order to master the vitrification process, it is important to determine the electrical properties of the nuclear glass in a large temperature range as well as to understand the motion of the charge carriers and the associated conduction mechanisms. The impedance spectroscopy method up to 1300 °C is used to determine the properties of both the molten glass and the self-crucible which is subjected to an important thermal gradient (from 500 to 1000 °C.cm-1). The evolution of the electrical conductivity with temperature for the studied glasses is in agreement with the Arrhenius and VTF laws in the solid and the molten states respectively, which are the representative behaviors of ionic conduction mechanisms. The effect of the presence of some elements such as RuO2 which induce electronic contribution on these evolutions is also investigated. Although borosilicate glasses used for nuclear waste management contain a large quantity of elements, their electrical conductivity is mostly controlled by the sodium cations provided that RuO2 content is less than a percolation threshold. Previous studies have shown that the presence of crystalline phases or phase separation phenomena modify the electrical properties of the materials and can be detected by impedance spectroscopy. In our case, the impact of these microstructure modifications due to the thermal gradient within the self-crucible on both electrical and dielectrical properties is investigated to fully understand and characterize the motion of charge carriers in the CCIM technology and master the nuclear waste vitrification process.
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