Tackling Structural Materials Challenges for Advanced Nuclear Reactors: Molten Salt Systems
Sponsored by: TMS Corrosion and Environmental Effects Committee, TMS Nuclear Materials Committee, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Miaomiao Jin, Pennsylvania State University; Xing Wang, Pennsylvania State University; Karim Ahmed, Texas A&M University; Jeremy Bischoff, Framatome; Adrien Couet, University of Wisconsin-Madison; Kevin Field, University of Michigan; Lingfeng He, North Carolina State University; Raul Rebak, GE Global Research
Monday 2:00 PM
October 10, 2022
Room: 330
Location: David L. Lawrence Convention Center
Session Chair: Weiyue Zhou, Massachusetts Institute of Technology; Adrien Couet, University of Wisconsin-Madison
2:00 PM Invited
Interfacial Interactions between Molten Salt and Structural Materials: Jinsuo Zhang1; 1Virginia Polytechnic Institute and State University
Structural materials degradation is a key concern of applications of molten salt in advanced nuclear reactors. The degradation is due to the interfacial interactions which include such as dissolution, oxidation, salt penetration and carbonization. In this presentation, we will cover the behaviors and mechanisms of these interactions and their impacts on material corrosion. We will consider both actinide- and fission product-bearing salts and clean salts to illustrate the effects of actinide and some major fission products. In addition, the presentation will discuss methods on how to inhibit the corrosion as well as a simple model to predict the corrosion kinetics in a non-isothermal nuclear coolant loop.
2:30 PM Invited
Elucidating Interfacial Phenomena in Molten Salt Corroded Nickel-Chromium Alloys using Analytical Transmission Electron Microscopy: Kaustubh Bawane1; Ruchi Gakhar1; Michael Woods1; Panayotis Manganaris1; Yachun Wang1; Jagadeesh Sure2; Arthur Ronne3; Phillip Halstenberg4; Simerjeet Gill2; Kotaro Sasaki2; Yu-chen Karen Chen-Wiegart3; Sheng Dai4; Shannon Mahurin4; Simon Pimblott1; James Wishart2; Lingfeng He1; 1Idaho National Laboratory; 2Brookhaven National Laboratory; 3Stony Brook University; 4Oak Ridge National Laboratory
Molten halide salts are used in various technologically important applications like molten salt reactors and concentrated solar power. A major challenge of molten salts is their corrosivity towards structural materials. However, most of the complex interfacial phenomena related to molten salt corrosion are not well understood. This talk will present an overview of transmission electron microscopy (TEM) techniques and associated spectroscopies such as energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) to understand key corrosion events and chemical processes at the interface. This talk will highlight our recent work on utilizing novel quasi in situ TEM technique to study time-dependent evolution of corrosion damage as well as the EELS technique to identify changes in oxidation states of dissolved alloying elements. This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center, funded by the U.S. Department of Energy Office of Science.
3:00 PM
Quantifying Cr and Fe Dissolution to Understand Stainless Steel Molten Salt Compatibility: Bruce Pint1; Dino Sulejmanovic1; Cory Parker1; Yi-Feng Su1; Rishi Pillai1; 1Oak Ridge National Laboratory
There is considerable interest in molten salts for several applications including next generation molten salt reactors (MSRs). Several MSR developers have targeted type 316H stainless steel as a near term structural material. Both static capsule and flowing thermal convection loop (TCL) salt (Cl and F) experiments have shown both Fe and Cr dissolution from 316H and indications of Fe mass transfer in TCL experiments. To further study the relative behavior of Fe and Cr, capsule experiments with unalloyed Fe or Cr specimens are being conducted at 550°-800°C for up to 2000 h. Specimen mass loss and salt chemistry are being compared to quantify the dissolution and assess any impact of the capsule material on the dissolution. A more fundamental understanding of 316H molten salt compatibility is needed to develop a predictive model to assist MSR development. Research sponsored by the U.S. Department of Energy, Office of Nuclear Energy, MSR Campaign.
3:20 PM Break
3:40 PM
Assessing Materials Susceptibility to Environmentally-assisted Cracking in Advanced Reactor Coolant Environments: Samuel Briggs1; Peter Beck1; Dustin Mangus1; Jake Quincey1; Xavier Quintana1; Guillaume Mignot1; Julie Tucker1; 1Oregon State University
Stress corrosion cracking, corrosion fatigue, and irradiation-assisted stress corrosion cracking are all complex materials degradation modes that are relatively well-understood in light water reactors. However, these phenomena are not well-studied in advanced reactor environments, where they are likely to manifest in significantly different ways due to higher temperatures and differences in the active corrosion mechanisms in non-aqueous coolant media. To investigate factors governing these behaviors, Oregon State University has recently developed unique test facilities capable of fracture mechanics-based EAC testing in liquid sodium and molten salt environments. These facilities combine some mechanical loading mechanism (e.g., a traditional electronic actuator) with a temperature controlled coolant environment of interest, enabling various environmentally-assisted crack growth tests within wide range of operational environments relevant to most preeminent advanced reactor designs. Results from preliminary slow strain rate tests in molten FLiNaK and U-bend tests in liquid sodium environments will be presented and discussed.
4:00 PM Invited
Imaging Local Vacancy Supersaturation in Metals After Corrosion in Molten Salt: Yang Yang1; Weiyue Zhou2; Sheng Yin3; Qin Yu3; Robert Ritchie3; Mark Asta3; Ju Li2; Michael Short2; Andrew Minor3; 1The Pennsylvania State University; 2MIT; 3LBNL
Localized corrosion is a critical damage initiation step that can lead to early failure and unforeseen disasters in engineering systems. The progression of localized corrosion is often accompanied by the evolution of porosities in materials, creating internal mass-flow pathways which facilitate the ingression of the external environment into the interior of the material. Here, we discovered an extremely localized form of corrosion, which we call one-dimensional (1D) wormhole corrosion, is responsible for the fast penetration of salt in Ni-20Cr. Combining four-dimensional scanning transmission electron microscopy (4D-STEM) and density functional theory (DFT) simulation, we further developed a vacancy mapping method with nanometer spatial resolution. Using our technique, we identified that the diffusion-induced grain boundary migration (DIGM) zone is the precursor of these 1D wormholes, and it possesses a vacancy fraction up to 100 times greater than that of metals close to their equilibrium melting points.
4:30 PM
Electrochemical Determination Kinetic Properties of Ni2+ and Cr3+/Cr2+ in FLiNaK Molten Salt: Nathan Smith1; Stephen Lombardo1; Hojong Kim1; Shunli Shang1; Zi-Kui Liu1; 1Pennsylvania State University
Understanding thermochemical properties of common corrosion products (i.e., Ni2+, Cr3+/2+) from structural materials used in molten salt reactors and loops is important for developing improved corrosion-resistance and in-situ monitoring systems. Electrochemical techniques including cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) were utilized to determine kinetic properties of Ni2+ and Cr3+/2+ in FLiNaK at T = 475–625 °C. Cyclic voltammetry and chronoamperometry were performed using a three-electrode cell to determine diffusivity as a function of temperature as well as corresponding activation energies. By varying concentrations of Ni2+ and Cr3+/2+ (e.g., 1 mol%, 0.1 mol%, 0.01 mol%) in FLiNaK, formal potentials were also estimated. Complementary characterization including X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and differential scanning calorimetry (DSC) were also employed to confirm and supplement electrochemical results.
4:50 PM
Correlated Characterization of Ni-based Superalloys Corroded in Uranium-containing Molten Salt Systems: Trishelle Copeland-Johnson1; Daniel Murray1; Guoping Cao1; 1Idaho National Laboratory
The United States Department of Energy is committed to the advancement of nuclear reactor technology through initiatives such as the Advanced Reactor Development Program (ARDP), to diversify the United States energy portfolio towards more sustainable energy options. The ARDP includes demonstration by industry partners of molten chloride salt fast reactors (MCFRs). Construction of molten salt reactor technology requires qualified nuclear structural materials. Unfortunately, there are no current materials that meet current qualification requirements dictated by the Nuclear Regulatory Commission for construction of MCFRs. Adapting current structural material qualifications requires expansion of our current knowledgebase on corrosion performance. In this investigation, we assess microstructural changes in a Ni-based superalloy after exposure to a uranium chloride-containing salt system through a correlated multi-modal approach combining several advanced characterization techniques. The findings from this investigation will further expand our assessment of the corrosion performance of structural materials being investigated for construction of MCFR components.