Materials and Chemistry for Molten Salt Systems: General Materials and Chemistry II
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee, TMS: Nuclear Materials Committee
Program Organizers: Stephen Raiman, University of Michigan; Raluca Scarlat, University of California, Berkeley; Jinsuo Zhang, Virginia Polytechnic Institute and State University; Kumar Sridharan, University of Wisconsin-Madison; Nathaniel Hoyt, Argonne National Laboratory; Michael Short, Massachusetts Institute of Technology

Wednesday 2:00 PM
March 2, 2022
Room: 203B
Location: Anaheim Convention Center

Session Chair: Stephen Raiman, Texas A&M University

2:00 PM  
High-throughput and Machine Learning Accelerated Discovery of Corrosion-resistant Alloy for Molten Salt Applications: Yafei Wang1; Bonita Goh1; Phalgun Nelaturu1; Thien Duong2; Najlaa Hassan1; Raphaelle David1; Michael Moorehead1; Santanu Chaudhuri2; Jason Hattrick-Simpers3; Dan Thoma1; Kumar Sridharan1; Adrien Couet1; 1University of Wisconsin-Madison; 2Argonne National Laboratory; 3National Institute of Standard and Technology
    Insufficient availability of molten salt corrosion-resistant alloys severely limits the deployment of a variety of promising molten salt technologies that could otherwise have significant societal impacts. To accelerate the alloy development for molten salt applications, a set of high-throughput alloy synthesis, corrosion testing, characterization, and modelling techniques were developed to examine the corrosion resistances of more than 100 FeCrMnNi alloys in molten salt. By using these techniques, the corrosion resistances were characterized and used as a performance metric for a random forest regressor machine learning algorithm to predict the most corrosion-resistant alloys in molten salt. The predicted corrosion-resistant alloys were further tested and their corrosion resistances were compared with the existing commercial alloys, such as Hastelloy-N, alloy 617, alloy 800 H and 316 stainless steel. This study demonstrates the successful deployment of an integrated platform to accelerate corrosion-resistant alloy development by about three orders of magnitude.

2:20 PM  
Mechanisms and Model Development for Molten Salt Corrosion: Jinsuo Zhang1; 1Virginia Polytechnic Institute and State University
    Extensive corrosion experiments have been conducted to understand the corrosion by molten salts, however, theoretically studies to understand the mechanisms are still scarce. In the present study, a corrosion model will be developed based on the corrosion mechanisms including the dissolution of pure metals, alloys and oxides, and mass transfer of corrosion products and corrosive impurities in the molten salt. The potential limiting process, that may determine the corrosion kinetics, is also discussed. The extension of the model can be applied to predict corrosion/precipitation in a non-isothermal molten salt loop under redox control.

2:40 PM  
In-situ Corrosion Monitoring of 316 SS L Natural Convection Loop by Radioactive Isotope Tracking: Yafei Wang1; Cody Falconer1; Aeli Olson1; Jonathan Engle1; Brian Kelleher2; Kumar Sridharan1; Adrien Couet1; 1University of Wisconsin-Madison; 2TerraPower, LLC
    There is a critical lack of molten salt corrosion studies under flow conditions mostly because of the challenges to quantify corrosion kinetics (dissolution/deposition) in these systems. This study explores the in-situ corrosion monitoring of a 316 SS L molten salt natural convection loop through the thin layer activation technique. Radioactive isotope tracers were generated by 12 MeV proton irradiation of a thinned down tube section on the hot leg. Using HPGE gamma-ray detectors located at different locations, the dissolution of the irradiated 316 SS L was in-situ monitored through the activity measurement of the radioactive isotope tracers. At the same time, the flow of the dissolved isotope tracers was also in-situ monitored at different loop locations. A mass transport model is then developed and validated by the in-situ activity measurements and post-corrosion SEM/EDS tube characterizations. This unique technique is effective for the in-situ corrosion monitoring study in flow conditions.

3:00 PM  
Thermal Gradient Mass Transport Corrosion in Molten Chloride Salts: Brian Kelleher1; Sean Gagnon1; Ivan Mitchell1; 1Terrapower
    A first-of-a-kind, small scale natural circulation loop has been developed at TerraPower for the evaluation of molten chloride salt corrosion in support of the Molten Chloride Fast Reactor (MCFR) program. This small-scale loop, or microloop, uses several hundred grams of salt to operate, making it ideal for polythermal corrosion studies with limited salt supplies. As of now, forty-five loops have operated or are currently operating, accruing over eight flow-years of data, some using uranium chloride. Mass transport corrosion created with the microloop is unique, and repeatable, although measurements of precise rates is difficult. This talk aims to discuss the design and operating characteristics of a loop, with a brief treatment of corrosion results.

3:20 PM Break

3:40 PM  
Thermodynamic Properties of Gd-Bi Alloys Determined by EMF Measurements in LiCl-KCl-GdCl3 Electrolyte: Stephanie Castro Baldivieso1; Nathan Smith1; Sanghyeok Im1; Hojong Kim1; 1Penn State University
    Thermodynamic properties of Gd in liquid Bi (mole fraction, xGd = 0.02–0.35) were investigated using electromotive force (emf) measurements in molten LiCl-KCl-GdCl3 at 700-1048 K for the design of enhanced recovery processes for Gd utilizing strong chemical interactions between Gd and Bi. The use of pure Gd(s) as the reference electrode resulted in erratic emf values by dissolution into the molten salt. To mitigate the high reactivity of pure Gd(s), this work developed a stable, two-phase Gd-Bi alloy (xGd = 0.16) as the thermodynamic reference electrode, calibrated by electrodepositing pure Gd(s) in 25 K increments between 700-1048 K. Using this reference electrode, the emf values of Gd-Bi alloys were determined via coulometric titration technique at 773–973 K, resulting in the solubility, activity coefficient, and the excess partial molar Gibbs energy of Gd in liquid Bi.