MSE PhD Final Defense of Anubhav Wadehra

TITLE: ADVANCED HIGH TEMPERATURE X-RAY STUDIES OF THE STRUCTURE OF MOLTEN FLUORIDE SALTS

ADVISOR: Karl Ludwig Physics, MSE

COMMITTEE: Uday Pal ME, MSE; Soumendra Basu ME, MSE; Srikanth Gopalan ME, MSE

CHAIR: Joerg Werner ME, MSE

ABSTRACT: The highly desirable properties of molten salts have generated a renewed interest in using them not only in Molten Salt Reactors (MSR) as fuel carriers, but in concentrated solar power, thermal storage systems, hydrogen production, oil refineries and as heat transfer fluids. LiF-NaF-KF (46.5-11.5-42 mol% - ‘FLiNaK’) and NaF-ZrF4 (53-47 mol%) are model MSR salts - the former salt is used as a heat transfer coolant and for thermal solar energy storage applications while the latter salt has been used as a fuel carrier and primary coolant. To understand the origin of the salt’s physical and chemical properties, it is important to have knowledge of its atomic structure.

This study will discuss the structural data of such molten fluoride salts as a function of temperature using high-energy x-ray scattering and x-ray absorption spectroscopy experiments that were conducted at Beamline 28-ID-1 at NSLS-II, Brookhaven National Lab and Beamline 5-BM-D at Advanced Photon Source, Argonne National Lab. Ab-initio Molecular Dynamics (AIMD) and Neural Network-based Molecular Dynamics (NNMD) simulation results obtained from collaborators will also be compared to experiments through the predicted pair distribution functions and coordination numbers as a function of temperature.

These findings contribute to a comprehensive understanding of the complex local structure of the molten salts, providing insights into temperature-dependent preferences and correlations within the molten system.