Design and Fabrication of a Thermodynamic Reference Electrode Using Chemical Vapor Deposition

Molten salt-cooled reactors have the potential to be significantly more efficient than other nuclear reactor designs, as they offer higher heat transfer capacity, higher operating temperature, and lower operating pressure. Thermodynamic reference electrodes (TRE) are necessary for control of the primary coolant chemistry, identifying air and/or moisture ingress into the coolant, and gauging structural material corrosion, all of which factor into the operational safety of the reactor. The stability and accuracy of TREs are currently limited by their materials of construction, which must be able to withstand hundreds of hours of thermal cycling in extremely corrosive conditions. Ultramet will develop a thermodynamic reference electrode for molten salt-cooled reactors that will be electrically insulated using chemical vapor deposited (CVD) coatings of materials such as boron nitride or silicon nitride. Additionally, CVD and/or other processes will be used to deposit lanthanum fluoride, a selectively permeable membrane for fluoride ions, on the internal surfaces of the TRE cell. CVD allows for the precise control of grain size and orientation and coating morphology, which will improve the properties of the insulator and membrane structures. This in turn will result in improvements to the thermomechanical properties, thermal shock resistance, and life expectancy of the TRE. The Phase I project will focus on the development of the TRE design and the optimization of CVD processes for the insulator and membrane coatings. The insulator and membrane materials will be chosen based on current standards in the literature and on expert advice provided by the SALT Research Group at the University of California, Berkeley. The development of these coatings will focus on material quality and consistency, which will improve the accuracy and resistance to corrosion of the TRE. Development of a robust, stable, and accurate TRE will aid in the development of a commercially viable molten salt reactor. The development of production-scale TREs for use in monitoring and controlling the redox potential of molten salts is pivotal to the safety of the molten salt reactor. The technology will be marketed to developers and manufacturers of molten salt reactors. Additionally, Ultramet will expand its TRE development for use in other applications that use molten salts, such as extraction of energy-intensive metals, carbon dioxide capture, energy storage, and the commercial production of novel materials such as carbon nanoparticles, nanodiamonds, and graphene.