Investigating the Structure of Molten Salts with Neutron Diffraction and Molecular Dynamics

Since the 1950s, high-temperature liquid melts of ionic salts have been of interest as a means of storing, transporting, and burning nuclear fuel as well as disposing of its waste. During experimentation with nuclear reactors based on molten salts in the 1960s, issues like leakage and material management surfaced, exposing the need for greater understanding of the behavior of molten salts. While interest in molten salt reactors declined through the 70s and beyond, new interest has revived in the 21st century as experimental and computational techniques have developed to allow more reliable investigations of molten salts. These advancements open the door to creating models that can accurately describe molten salt behavior. We performed neutron diffraction experiments on several promising salt mixtures to probe the spatial correlations between the ionic species. Using Python code, we developed tools that enable the efficient comparison of simulated salt mixtures to the observed data, showing that molecular dynamics simulations provide a good description of the salt structure. We are also developing code to simulate time-dependent ionic correlations, which will provide greater opportunities to test the reliability of simulated molten salt behavior when compared to empirical observations. This work supports the efforts to run cheap, reliable, and accurate simulations to predict molten salt behaviors in untested situations and efficiently develop new molten salt reactor technologies.