(289e) Density Measurement of Actinide Chloride Molten Salt Systems By Neutron Radiographic Dilatometry

In 2021, Melt point, enthalpy of fusion, and volumetric expansion of single- and multi-component liquid chlorides {NaCl, KCl, LiCl, MgCl₂ , CaCl₂, UCl₃} were measured experimentally. These properties and materials are relevant in applications such as heat transfer, liquid nuclear fuel, and pyrochemical processing. A novel method for density measurement by neutron radiography was shown to produce high-quality data, consistent with reference literature where available, and allowed measurement of some materials for the first time. This method is especially useful in the characterization of sealed sample crucibles, given the ability of neutrons to penetrate the containment and surrounding furnace material. The results of this study are presented within the context of a comprehensive review of the available published data. The purpose of this review is to integrate measurements of the thermophysical properties of liquid chlorides into empirical descriptions of the relationships between composition, temperature, and thermophysical properties. A model for the prediction of the density of mixtures of liquid chlorides is proposed and demonstrated within a case study of the {NaCl + x mol% UCl3} system. These results have been published, and will be presented here.

Recently, PuCl₃ bearing samples were prepared at the Plutonium Facility, shipped to the Los Alamos Neutron Science Center (LANSCE), and radiographed with the density via neutron radiography technique described previously. Density data in the form of meniscus heights were recorded as a function of temperature. The results show a linear dependence of density with temperature and a third order polynomial dependence of density with composition as a function of PuCl₃ addition in the corresponding halide salt mixture. Additions of PuCl₃ result in a significant increase in density of the salt mixture and a slight reduction in the coefficient of volumetric expansion. These results represent a first measurement of the density of plutonium chloride salt mixtures, which once fully analyzed, will lead to a generalized description of the density of such salt systems for arbitrary compositions and temperatures. These plutonium results have yet to be published and will be discussed at the time of the conference.