The design and development of fully functional Molten-Salt Reactors (MSR) require detailed knowledge of the molten salt properties in order to predict the salt’s behavior in the presence of impurities such as fission and corrosion products. Fundamental properties of interest include molecular structure and speciation, as well as the connection between the structure and viscosity and ionic mobility. Since the chemical composition of the salt changes due to the addition of the corrosion and fission products, computer modeling is necessary to predict the physical and chemical properties of the melts across the vast phase space. The modeling requires measurement data, and advanced neutron and x-ray scattering and spectroscopy provide the most reliable and direct determination of the structure (Pair-Distribution Functions, PDF), and dynamics (diffusion coefficients). <i>Ab initio </i>molecular dynamics simulations will be performed to understand the multi-component liquid solution, in particular, the solubility of impurities and thermodynamic interactions in relation to the ionic-cluster structure of the fluid. We are applying machine learning to regress from the simulation and experimental data in order to develop a fast-acting model that can handle molten salt with arbitrary (&gt;10) number of chemical elements and be able to predict chemical potential as a function of composition and temperature.<br/><br/>In particular, we’re studying the NaCl-CrCl3 and NaCl-CrCl2 mixtures in order to deduce the speciation and dynamics of Cr ions, the most important corrosion product in molten salts and help to determine the oxidation state of Cr ions in the reactor salts. Elastic neutron scattering will take advantage of a very large contrast between the coherent scattering lengths of 52Cr and 53Cr. The current state of this project will be reported.

Determination of molecular structure and dynamics of molten salts by advanced neutron and X-ray scattering measurements and computer modeling

2019 Fall National Meeting

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