Design and performance of a molten fluoride salt-compatible optical thermophysical property measurement system

Accurate knowledge of molten salt thermophysical properties is crucial to optimize the efficiency, safety, and reliability of molten salt based energy applications. For molten fluorides, currently of high interest for fission and fusion reactors, data regarding these properties are either poor or non-existent. Thermal diffusivity and sound speed in particular play important roles in the modeling of a reactor's steady state, transient, and accident scenarios. Fluoride salt-compatible property measurement systems have thus far been the bottleneck in accurately obtaining these properties. We present the design of an optical system optimized for molten fluoride salt thermophysical property measurement, along with characterization of its thermal performance. Demonstration of system capabilities is achieved through acquisition of sound speed and thermal diffusivity in lithium chloride (LiCl), showing excellent agreement with literature data.