Materials and Chemistry for Molten Salt Systems: Salt Properties and Fundamental Science
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Stephen Raiman, University Of Michigan; Jinsuo Zhang, Virginia Polytechnic Institute and State University; Michael Short, Massachusetts Institute of Technology; Kumar Sridharan, University of Wisconsin-Madison; Nathaniel Hoyt, Argonne National Laboratory
Wednesday 2:00 PM
February 26, 2020
Room: Theater A-6
Location: San Diego Convention Ctr
Session Chair: Jinsuo Zhang, Virginia Polytechnic Institute and State University
2:00 PM
In-situ Spectro-electrochemistry of Molten Chloride Salts: Ruchi Gakhar1; William Phillips1; Steven Frank1; 1Idaho National Laboratory
Known historically as electrochemical media for high temperature processes, molten salts have regained the attention of the community for their use in advanced nuclear and solar thermal power plants. Owing to the structural complexities of fused salt systems, the chemical properties of these mixtures depend on melt composition and temperature in intricate ways, borne out primarily by changes in coordination geometry around the metal ions in the melt. In addition to the formal charge on the metal ion, the polarizing power of the bulk melt cation and the octahedral site preference energy are the primary factors defining the coordination geometry. To understand the metal speciation in molten salt systems, a novel and versatile spectro-electrochemical furnace has been designed at Idaho National Laboratory for in-situ spectroscopic and electrochemical measurements. Variations in coordination chemistry for transition metal chlorides as a function of salt melt composition, temperature and analyte concentration will be discussed.
2:20 PM Student
Thermophysical-properties Characterization of a Quaternary Novel Salt based on Na+/K+ and NO3-/Cl- System: Matias Castro Quijada1; Daniel Faundez1; Carlos Lopez2; Alvaro Videla1; 1Pontificia Universidad Católica de Chile; 2Salmag, Albemarle
The energy efficiency of the CSP Tower Plants (CSPTPs) can be improved by using a HTF (Heat Transfer Fluid) that works in a higher thermal range than current solar salts. The so-called 2nd CSPTPs generation, with HTF based on Sodium-Potassium nitrates, has a regular thermal range of operation (520-850K). Recent research for the 3rd CSPTPs generation has identified chlorides salts (670-1070K) as an attractive alternative HTF to solar salts. The present work research on a transitional path shifting from a 100% nitrates solar mixture (36:64 molar of K:Na) towards a 50% nitrates & 50% chlorides mixture (50:50 molar of K:Na). Along this presentation, results are shown regarding the variation of properties such as melting temperature, degradation temperature, HTF viscosity, and energy density as function of chloride addition to the solar salt. The laboratory characterization includes DSC, TGA, viscosity and density measurements by standard methods.
2:40 PM Student
Kinetic Properties of Fe2+/Fe, Ni2+/Ni, Cr2+/Cr and Cr3+/Cr Reactions in Molten MgCl2-KCl-NaCl Salt: Qiufeng Yang1; Jinsuo Zhang1; 1Virginia Tech
Reliable measurement of exchange current density i0 is important for systems with molten salt as electrolyte or heat transfer fluid. i0 of Fe2+/Fe, Ni2+/Ni, Cr2+/Cr, Cr3+/Cr reaction in MgCl2-KCl-NaCl at different temperatures (600°C-800°C) and concentrations (1wt%-0.01wt%) are reported, which are determined by non-linear curve fitting method using modified kinetic equation with mass transfer effect considered. It’s confirmed that significant errors can be introduced using conventional techniques, i.e., Tafel plot, polarization resistance and electrochemical impedance spectroscopy, which result from multiple assumptions during calculations. The standard rate constant k0 of Fe2+/Fe estimated by curve fitting method are 4.5356-9.0323×10-4 cm/s in this study. Relation of lnk0 and 1/T demonstrates good linearity, which indicates that temperature dependence of k0 obeys Arrhenius law.
3:00 PM Student
Molten Salt Property Determination and Corrosion Characterization Using Transient Grating Spectroscopy: Sean Robertson1; Michael Short1; 1Massachusetts Institute of Technology
In order to optimize the design process for molten salt applications, data regarding salt properties and material compatibility must be readily available for a variety of salt compositions. Of particular interest and need are data regarding corrosion kinetics in molten salts. Due to their high melting points and corrosive nature, fluoride salts have proven difficult to analyze to date, limiting their potential impact. Transient Grating Spectroscopy (TGS) offers a potential means of determining molten salt properties such as thermal diffusivity, sound speed and viscosity, while also providing a mechanism for in-situ corrosion monitoring. In order to harness this technique, a high-temperature TGS setup for molten fluorides has been designed and tested. Initial results and a system design overview will be discussed.
3:20 PM Break
3:40 PM
Thermochemical Modeling and Development of the MSTDB Database for Simulating Molten Salt Reactors: Theodore Besmann1; Kaitlin Johnson1; Johnathan Ard1; Jacob Yingling1; Vancho Kocevski1; Matthew Christian1; Jacob McMurray2; Stephen Utlak2; Markus Piro3; 1University of South Carolina; 2Oak Ridge National Laboratory; 3Ontario Tech
Molten salt reactors (MSRs), with salt as the fuel/coolant or solely the coolant, requires a close understanding of salt properties to be able to simulate normal and off-normal operations. Among the most important are the thermochemical properties of the salt, that is the Gibbs energy relations for the complex liquid and solid solutions as these provide thermal properties as well as critical phase equilibria such as solidus and liquidus. Models for the pseudo-binary and -ternary fluoride and chloride salt systems are being compiled, and where necessary developed, to provide a thermochemical resource. The molten salt thermochemical database (MSTDB) is being implemented with the thermochemical solver THERMOCHIMICA in prospective MSR simulation codes for use in reactor design, simulated reactor operations, and assessment of off-normal scenarios to support regulatory activities. The presentation will cover current modeling and development of MSTDB, and provide the context for its use in reactor simulation.
4:10 PM
Development of Experimental Vehicle Technology for the Versatile Test Reactor to Investigate the Effects of Fast Neutron Irradiation on Molten Salts: Adam Burak1; Sheng Zhang1; Xiaodong Sun1; 1University of Michigan
Understanding molten salt and containment behavior under irradiation is a key consideration that needs to be addressed to bring Molten Salt Reactor (MSR) concepts to fruition. The Versatile Test Reactor (VTR) presents an opportunity to study the effects of fast neutron irradiation. A platform is being developed for the proposed VTR design which can record multiple real time data streams and collect salt samples, providing a rich source of information. Feasibility testing and development of the instrumentation for this platform are being performed using a stainless steel mockup. Chloride salts were received from collaborators at the University of Utah and used to test the functionality of the system. Several process parameters were recorded: pressure, redox potential, heater power, and temperature at several positions. Salt samples were collected, testing a differential pressure salt sampling concept, and then sent to collaborators at Virginia Commonwealth University to develop ex situ chemical analysis techniques.