Materials and Chemistry for Molten Salt Systems: Novel Materials and Properties
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; Michael Short, Massachusetts Institute of Technology; Kumar Sridharan, University of Wisconsin-Madison; Nathaniel Hoyt, Argonne National Laboratory
Tuesday 8:00 AM
March 21, 2023
Room: 27A
Location: SDCC
Session Chair: Kumar Sridharan, University of Wisconsin
8:00 AM
Microstructural Evolution and Hardness Changes in Ion irradiated Ni-based Superalloys: Qinyun Chen1; Ryan Thier1; Yan-Ru Lin2; Wang Ling3; Steven Zinkle1; 1University of Tennessee; 2Oak Ridge National Laboratory; 3SLAC National Accelerator Laboratory
Nickel-based superalloys are promising structural material candidates for molten salt reactors and other advanced nuclear energy systems. However, traditional Ni alloys such as Inconel 718 and Nimonic PE16 exhibit severe mechanical degradation after irradiation. Several high-performance commercial Ni-base superalloys, including Haynes 282 and solid solution strengthened and precipitation strengthened Haynes 244, were irradiated with 8 MeV Ni ions to midrange doses of 1 and 10 dpa at 600 ℃ and 750 ℃. Microstructural changes and mechanical properties were characterized by GIXRD, cross-section TEM, and nanoindentation. With increasing irradiation dose at 600 ℃, the hardness of Haynes 244 with different pre-irradiation heat treatments significantly increased, while the hardness of Haynes 282 showed an overall trend of slight decrease and subsequent increase. Mechanical behavior will be explained based on microstructural changes regarding the size and density of precipitates and dislocations as a function of irradiation temperature, dose, and precipitate type.
8:20 AM
Interest of Nickel Based Alloys Additive Manufacturing for Molten Salt Reactors: First Elements of Behavior under Ion Irradiation.: Martin Madelain1; Pascal Aubry1; Alexandre Legris2; Yann de Carlan1; 1Université Paris-Saclay, CEA; 2UMET, Polytech Lille
Additive manufacturing (AM) is a booming technology that offers new perspectives for industry. In the nuclear industry, Molten Salt Reactors are developing fast and AM can be useful in designing and producing different parts for those reactors. Harsh conditions are expected for the components, including irradiation and molten salt corrosion. The characteristics of AM materials under these conditions must be investigated to ensure acceptable performance. In this study, superalloys (Hastelloy X, Inconel 718, ABD-900AM) and 316L steel were manufactured with laser power bed fusion (LPBF). The microstructural characterizations have shown a good quality of manufacture and a Fe5+ ion irradiation campaign was carried out at 550 °C in the JANNuS installation (CEA Saclay). The purpose of this irradiation was to obtain high dose (>100 dpa) to study the swelling under irradiation. Thanks to the characterizations carried out by Transmission Electron Microscopy, the behavior under irradiation of the alloys is discussed.
8:40 AM
Residual Stress in Cobalt Free Cladding Systems for Molten Salt Reactors: Behrooz Tafazzolimoghaddam1; Richard Moat1; 1The Open University
Cobalt alloys used in hard facing cladding layers accounts for the greatest proportion of gamma exposure in nuclear plant workers. Therefore, replacing the cobalt alloys in new designs is a priority. Unfortunately, replacement alloy systems that replicate the performance of cobalt-based alloys are not readily available. In this study we present structural integrity assessment conducted on PTA deposited nickel-base hard facing alloys, highlighting some of the difficulties in replacing cobalt alloys with nickel alloys, namely cracking and residual stress formation.
9:00 AM
ICME Development of a Cold Spray Enabled Corrosion Resistant Bimetallic Structure for Nuclear Reactors: Pin Lu1; Joseph Heelan2; Vilupanur Ravi3; 1QuesTek Innovations LLC; 2Solvus Global; 3Cal Poly Pomona
Bimetallic structure consisting of a corrosion resistant surface layer joined on top of ASME code approved structural materials has become a promising solution to address the corrosion issue in molten salt reactors. This DOE-funded program aims to develop cold spray enabled bimetallic structures with a refractory-based coating on ASME code-certified substrate. ICME technologies were employed to design alloy compositions that combine improved cold spray processability with high molten salt corrosion resistance and strong interfacial bonding. Initial cold spray trials depositing these compositions on 316 stainless steel substrate were successfully performed. Coatings were proved to be of high quality by metallographic inspection and have strong adhesion by button pull adhesion testing. Molten salt test protocols have been developed. Cold spray materials were tested and characterized post corrosion test. Observations indicated that all alloy compositions were promising in terms of corrosion resisting performance after 750°C for 100 hours in molten chloride salt.
9:20 AM
Corrosion Behavior of Compositionally Gradient Additively Manufactured 316L Stainless Steel Doped with Hafnium in Eutectic NaCl-MgCl2 Molten Salt at 700 °C: Laura Hawkins1; Jingfan Yang2; Michael Woods3; Trishelle Copeland-Johnson3; Ruchi Gakhar3; Lin Shao1; Xiaoyuan Lou2; Daniel Murray3; Lingfeng He3; 1Texas A&M University; 2Purdue University; 3Idaho National Laboratory
Classification of structural materials for next generation molten-salt reactors must consider corrosion of the salt-facing components. This study combines additively manufactured (AM) high-throughput materials characterization with molten salt corrosion to demonstrate the effects of hafnium dopants on corrosion behavior. The AM 316L stainless steel samples are submerged in eutectic NaCl-MgCl2 molten salt at 700 °C for 30 and 120 hours. The morphology and microstructure of the gradient region after the corrosion tests are analyzed using scanning electron microscopy and transmission electron microscopy equipped with energy dispersive X-ray spectroscopy to understand intergranular corrosion, quantify Cr leaching and corrosion rates, and characterize corrosion by-products. The increased attack of grain boundaries as a function of time and the effect of hafnium gradients on corrosion rates will be presented.
9:40 AM Break
9:55 AM
Investigate on Dechromization in Converter during Vanadium Extraction and Semi-steel Steelmaking Processes Based on the Ion and Molecule Coexistence Theory: Wang Zhou1; Zhao Chen1; Xiaoxi Chen1; Bailin Luo1; Changfa Zhou1; Gai Fu1; Xiaowen Yu1; 1Chongqing CEPREI Industiral Technology Research Institute Co., Ltd.
A thermodynamic model has been developed to investigate the effects of basicity, temperature and carbon content on chromium removal during vanadium extraction and semi-steel steelmaking processes, based on the ion and molecule coexistence theory (IMCT). The results indicate that the carbon content in semi-steel and molten steel has the greatest influence on chromium removal, followed by smelting temperature and basicity of slag. Low carbon content, low smelting temperature and high basicity are conducive to chromium removal. Hence, in order to ensure the smooth operation of the subsequent steelmaking process, it is difficult to reduce the chromium content in semi steel to a lower level during vanadium extraction process. The chromium content in molten steel can be reduced to 0.004 wt.% during semi-steel steelmaking process while the carbon content in molten steel is 0.03 wt.%, the smelting temperature is 1923 K, and the basicity of slag is 3.0.
10:15 AM
Thermal Conductivity Measurements of FLiNaK, FMgNaK, and LiCl-KCl: Troy Munro1; Ryan Ruth1; Brian Merritt1; Benjamin Wright1; Noah Cahill1; Noah Cahill1; 1Brigham Young University
Of the different thermophysical properties needed to predict molten salt behavior within a reactor system, one of the most difficult properties to predict and measure is thermal conductivity (k). Because thermal conductivity determines the temperature gradient within molten salt and is necessary to determine the heat transfer coefficient between the salt and its surroundings, the current dearth of accurately measured data in the literature must be addressed. We present experimental results on the thermal conductivity of LiF-NaF-KF, NaF-KF-MgF2, and LiCl-KCl using a Modified Transient Hot Wire needle probe. Measurements were taken from the melting point of the salt to 750 °C, with uncertainties between 15-20%, thermal conductivity values between 0.49-0.85 W/m K, and a negative dk/dT that has been observed in unary salts. These results demonstrate a new capability that can measure thermal conductivity of halide salts relatively quickly (2-5 days per salt) to populate the necessary thermophysical property databases.
10:35 AM
Cover Gas Selection for Molten Salts: Adam Burak1; Minghui Chen2; 1University of Michigan; 2University of New Mexico
Results are presented from a literature review performed to evaluate cover gas candidates for molten salt systems. Three cover gases typically used with molten salts are considered: argon, helium, and nitrogen. Chemical compatibility is investigated by considering the reactivity of the gases with the salts, and with the containment materials. Gas solubility in molten salts is also addressed. Cover gases also frequently serve a secondary purpose as cooling gases. Heat transfer performance of cover gases is examined to assess their relative performance at different temperatures. Radiological concerns are studied by calculating the equilibrium radioactivity under thermal and fast neutron fluxes. Cost is addressed in a miscellaneous section. It is concluded that no cover gas is clearly ideal. Rather, the optimal choice depends on the specific system being considered. Gas selection criteria are compiled in a table to facilitate assessment for specific situations.
10:55 AM
Uncertainty Quantification and Propagation for Thermodynamic Models of Molten Salts: Jorge Paz Soldan1; Jacob Yingling1; Juliano Schorne-Pinto1; Johnathon Ard1; Mina Aziziha1; Clara Dixon1; Ronald Booth1; Amir Mofrad1; Theodore Besmann1; 1University of South Carolina
The application of uncertainty quantification and propagation (UQ & UP) in thermodynamic modeling has been a topic of interest in the last couple of decades in the CALculate PHAse Diagrams (CALPHAD) community. This is because a quantified understanding of the uncertainty of phase boundaries and thermodynamic properties based on the available data and selection of models in a database has large intrinsic value. One example is that through UQ & UP one can identify more effectively the chemical regions of interest that require additional measurements in order to improve prediction reliability while minimizing the number of experiments This presentation will use the open source ESPEI software to demonstrate how UQ & UP can serve in the advancement of the Molten Salt Thermal Properties Database − Thermochemical (MSTDB−TC) designed to support development of molten salt nuclear reactors, particularly as they relate to corrosion processes.