Thermodynamic Reference Electrodes for Molten Salt Systems

Advanced nuclear technologies use molten salts including chloride, fluoride, and other high- temperature variants in reactors and fuel processing equipment. These molten salts enable high- temperature applications over 600 °C offering advantages as fuel salts, coolants, and electrolytes. However, the aggressive nature of these molten salts can vary the salt chemistry along with corroding structural materials, thus, it is desired to monitor the molten salt redox state. Accordingly, thermodynamic reference electrodes are needed that can provide a stable potential helping to inform knowledge regarding the salt redox state. This Phase I program will develop a new thermodynamic reference electrode overcoming limitations with present-day designs that exhibit corrosion and instability due to chemical incompatibility of the reference electrode materials to the molten salt state, and due to thermal stress induced by cycling the reference electrode to high temperatures that physically destroy the reference electrode. The reference electrode developed in this program will focus on fluoride salts saturated with nickel fluoride using the Ni/Ni(II) redox couple. This reference electrode will enable higher accuracy, stability, and reliability for monitoring molten salt electrolytes over six-month long operating periods. This in turn will enable nuclear reactor designers and operators a better tool to improve the design and operation of nuclear processes including fusion and fission reactors.