ThorCon is a thermal spectrum, graphite moderated, molten fluoride fuel salt reactor. ThorCon implements a fully passive approach for Control (reactivity excursions and physics-based passive shutdown), Cool (decay heat removal) and Contain (radioactive material containment) to safely and economically handle possible casualty scenarios. As the molten fluoride fuel salt circulates, it continuously evolves as transmutations, fission product generation, structural material constituents dissolution, salt ingress into graphite pores, off-gassing, precipitation of insoluble species, temperature cycling, etc., occur. ThorCon fuel’s performance is, therefore, a function its current nuclear, chemical, and physical properties and fortunately, dynamic chemical equilibrium is achieved rapidly due to the high operating temperature effect on the kinetic processes. An adequate database of fuel salt property variances with temperature and composition is highly desirable. Measurements of fuel salt properties via sensors, even noncontinuous, will provide near real-time information on the physical and chemical state of the working fluid. Demonstration of the bounding values of the fluoride salt chemistry to include fission product solubility limits and purified salt acceptable impurity levels, facilitates reactor design for safe and economic operations. Similarly, measurements of the fuel salt oxidation state (represented in the Molten Salt Reactor Experiment as the ratio of U+4 to U+3 ions); and heat transfer parameters such viscosity, density, thermal conductivity, and heat capacity, and their rates of change (temperature and composition) are coveted.