Thermal Conductivity Characterization of Fluoride and Chloride Molten Salts Using a Modified Transient Hot-Wire Needle Probe

Molten salts are being widely considered for use as high-temperature coolants in advanced nuclear reactors. There are a serious lack of experimental data pertaining to their thermophysical properties, especially thermal conductivity, which are paramount to safe thermal hydraulic design. This study seeks to measure the thermal conductivity of several molten fluoride and chloride salts using a modified transient hot-wire needle probe. Building on previous work by the same authors, the multilayered heat transfer model is expanded to account for thermal radiation interactions across the salt layer and is validated using a commercial finite-element package. Sensitivity and correlation analyses are performed to assess the time-dependent influence of critical parameters in the model, including the new radiative terms. Finally, thermal conductivity measurements are presented for LiF–NaF–KF, NaF–KF–MgF₂, and LiCl–KCl up to 750 °C and are compared against reference correlations. Total measurement uncertainty is also quantified and tabulated, with the resulting range between ± 14.2 % and ± 29.0 %.