Investigating the thermophysical properties of molten salt mixtures for nuclear applications

Abstract

The successful deployment of next-generation small modular reactors (SMRs) depends on coolant salts with favorable thermophysical properties and operational reliability. NaCl–MgCl₂ is a strong candidate due to its low vapor pressure, wide liquidus range, and excellent heat transfer capabilities. This thesis presents an integrated experimental and modeling investigation of NaCl–MgCl₂ mixtures, benchmarked with FLiNaK and LiF–KF to validate procedures. Differential scanning calorimetry (DSC) was used to determine melting points and heats of fusion. FactSage modeling provided phase diagrams, vapor pressure trends, and dehydration pathways, supporting salt preparation and data interpretation. DSC results for NaCl–MgCl₂ reveal a eutectic melting range lower than predicted by FactSage, indicating a need to update its thermodynamic database. The study enhances understanding of chloride-based systems, confirms the effectiveness of purification protocols, and provides a foundation for future work on heat capacity, thermal conductivity, and SMR-compatible salt compositions.