Physicochemical properties of molten salts: scientific research and technological applications

 

O.Yu. Tkacheva and Yu.P. Zaikov

 

Institute of High Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia

 

Molten salts, due to their unique physical and chemical properties such as low density, viscosity, volatility in a wide temperature range, but high electrical conductivity, thermal conductivity, heat capacity, are widely used in various technological processes. Among the large-scale technologies based on physical and chemical transformations in molten salts are the production of aluminum, calcium, magnesium, lithium, and zirconium. High temperatures result in high process rates, which significantly impacts the production efficiency. In recent years, a new direction in the application of molten salts has been actively developing, associated with Generation IV nuclear reactors. In particular, the process of reprocessing spent nuclear fuel with a high burnup rate for fast neutron reactors cannot be carried out in aqueous media and requires the creation of new technologies. Molten salt nuclear reactors designed for the transmutation of minor actinides involve the use of molten halide mixtures as both a fuel salt and a coolant.
The Institute of High Temperature Electrochemistry has vast experience in studying both fundamental (crystallization temperature, electrical conductivity, density, viscosity, etc.) and special (vapor pressure, heat capacity, thermal diffusivity, speed of sound, etc.) properties of molten salts. Based on the available modern unique equipment and new methodological approaches, the Institute creates innovative technologies in the field of nuclear energy, non-ferrous metallurgy, electroplating, etc. Thus, important results have been achieved in the field of developing resource-saving and eco-friendly technologies for the aluminum industry. The production of aluminum by low-temperature electrolysis, as well as the synthesis of aluminum alloys by a combined method of electrochemical and metallothermic reduction of oxides dissolved in molten mixtures are characterized not only by a radical reduction in the operating temperature, while maintaining the sufficient oxides solubility, but also by performing the process in cells with inert (non-consumable) oxygen-releasing anodes.