Materials and Chemistry for Molten Salt Systems: Corrosion 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
Monday 2:00 PM
February 28, 2022
Room: 203B
Location: Anaheim Convention Center
Session Chair: Jinsuo Zhang, Virginia Tech
2:00 PM
Multi-modal Characterization of Interfacial Corrosion of Ni-based Alloys in Chloride-based Molten Salts: Trishelle Copeland-Johnson1; Michael Woods1; Ruchi Gakhar1; Guoping Cao1; Lingfeng He1; 1Idaho National Laboratory
Chloride molten salts have mounting interests as abundantly available heat transfer fluids for advanced nuclear reactor technologies and concentrated solar energy applications. However, corrosion behavior of structural materials in contact with molten chloride salts needs to be further assessed to establish corrosion performance limitations. This presentation will discuss multi-modal characterization of Ni-based alloys, such as Hastelloy C-276 and Inconel 617, exposed to eutectic molten chloride salt mixtures. Changes in the speciation of the molten salt alongside the structural and chemical composition of corrosion products and remaining structural material at the salt-alloy interface will be captured using optical spectroscopy and electron microscopy techniques. Overall, the potential impact of this study is to expand on the knowledgebase of materials corrosion data for chloride molten salts, in turn enhancing potential corrosion mitigation strategies.
2:20 PM
Static Corrosion of 316 Stainless Steel Upon Exposure to Metal Fluorides in Molten Salt: Ryan Hayes1; Sean Mills1; Andrew Minor1; Raluca Scarlat1; 1University of California Berkeley
Widely used in light-water reactors, austenitic 316 stainless steel has been proposed as a candidate material for generation IV reactor concepts. In fluoride salts, the oxide layer that typically protects this alloy from corrosion is removed due to its high solubility. In order to safely operate the fission and fusion reactors that will utilize molten fluoride salts as coolants or fuels, it is paramount that the effects and mechanisms of stainless steel corrosion be well understood. A coupon of 316 stainless steel was exposed to FLiNaK for 50 hours at a temperature of 600 °C. In this salt, dissolved iron(iii) fluoride served as an oxidant to corrode the steel sample. This presentation will focus on the effects dissolved oxidant concentration, comparing the corrosion of this sample with the corrosion of another 316 stainless steel coupon by nickel(ii) fluoride in FLiBe.
2:40 PM
Study of the Influence of Metal Ions on the Kinetics of Molten Salt Corrosion with Transmission Electron Microscopy and In situ Synchrotron X-ray Nano-tomography: Xiaoyang Liu1; Xiaoyin Zheng1; Kaustubh Bawane2; Michael Woods2; Mingyuan Ge3; Phillip Halstenberg4; Sheng Dai5; Xianghui Xiao3; Wah-Keat Lee3; Shannon Mahurin6; Ruchi Gakhar2; Lingfeng He2; Yu-chen Chen-Wiegart7; 1Stony Brook University; 2Idaho National Laboratory; 3Brookhaven National Laboratory; 4University of Tennessee; 5University of Tennessee/ Oak Ridge National Laboratory; 6Oak Ridge National Laboratory; 7Stony Brook University/ Brookhaven National Laboratory
Understanding the corrosion of alloys in molten salts is important to the development of sustainable energy systems. Metal ions from dissolved fission products and structural materials alter the reaction kinetics between the metals and the salts. Prior microscopic studies on reacted samples highlighted the importance to understand the morphological and chemical changes of the materials in molten salt corrosion. In this work, the corrosion of the eutectic KCl-MgCl2 with 1 wt.% of NiCl2, EuCl3 and CeCl3 on Ni-20Cr at 700°C was studied. In situ synchrotron X-ray nano-tomography was used to visualize and quantify the evolution of the morphological changes of Ni-20Cr alloys. The corroded Ni-20Cr and salt were further characterized by transmission electron microscopy coupled with spectroscopy. The influence of the additives on the kinetics of the corrosion is discussed to compare the differences in the development of a porous structure in these systems.
3:00 PM
Effect of Impurities on Stability of Graphite in Molten FLiNaK: Krishna Moorthi Sankar1; Preet Singh1; 1Georgia Institute of Technology
MSR Reactor designs include the use of several types of carbon-based refractory ceramic materials for reactor core components, including use of graphite for the fuel, moderators, and reflectors. It has been shown previously that the interaction of graphite with the structural materials may accelerate the corrosion of structural alloys in molten salts. It has also been demonstrated that the presence of impurities in fluoride molten salts can change the corrosion behaviour of structural alloys in molten salts. However, the effect of impurities in the molten fluoride salts on graphite have rarely been studied so far. This presentation will discuss the stability and behaviour of nuclear graphite in molten FLiNaK salt at 700 oC, and how this behaviour changes with the addition of different impurities such as oxides, metal fluorides, and metallic lithium to the salt.