Thermodynamic properties of ZrCl4 with LiCl, NaCl, KCl, CsCl, MgCl2, and UCl3 for molten salt reactor applications

Abstract

A set of self-consistent Gibbs energy functions has been developed to describe the thermochemical behavior of the major reactive fission product ZrCl4 with key components in chloride molten salt reactors (MSRs): LiCl–ZrCl4, NaCl–ZrCl4, KCl–ZrCl4, CsCl–ZrCl4, MgCl2–ZrCl4 and UCl3–ZrCl4. Low ZrCl4 concentration phase equilibria most relevant to MSR applications have been confirmed via differential scanning calorimetry for NaCl–ZrCl4, and X-ray diffraction analysis performed on equilibrated samples of NaCl–ZrCl4, KCl–ZrCl4, MgCl2–ZrCl4, and UCl3–ZrCl4. Within the framework of the modified quasi-chemical model in the quadruplet approximation, extrapolations of pseudo-binary models were generated to represent KCl–MgCl2–ZrCl4, KCl–NaCl–ZrCl4, and MgCl2–NaCl–ZrCl4, which show agreement with phase equilibria data where available without the use of ternary interaction parameters. The optimized thermodynamic descriptions for these systems and others are available in the open-source compendium Molten Salt Thermal Properties Database – Thermochemical (MSTDB–TC).