Tackling Structural Materials Challenges for Advanced Nuclear Reactors: Advanced Structural Materials
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 8:00 AM
October 10, 2022
Room: 330
Location: David L. Lawrence Convention Center

Session Chair: Miaomiao Jin, Pennsylvania State University


8:00 AM  
Mechanistic Calculation of the Effective Silver Diffusion Coefficient in Polycrystalline Silicon Carbide: Application to Silver Release in AGR-1 TRISO Particles: Pierre-Clement Simon1; Larry Aagesen1; Chao Jiang1; Wen Jiang1; Jia-Hong Ke1; 1Idaho National Laboratory
    The silicon carbide (SiC) layer in tristructural isotropic (TRISO) fuel particles serves as a barrier to prevent the escape of fission from the fuel kernel. The release of silver (Ag) is a concern due to the long half-life of the 110mAg isotope. In this study, the effective diffusion coefficient of the fission product Ag through the grain boundary (GB) network is calculated using a combination of atomistic and phase-field methods. Atomistic calculations of Ag diffusivity in SiC bulk and GBs are leveraged to develop a mesoscale effective Ag diffusion coefficient (Deff) in SiC. Since GBs serve as pathways for Ag diffusion, Deff is defined as a function of temperature, microstructure variables, and fluence. Deff is implemented in the fuel performance code Bison to predict Ag release from AGR-1 TRISO fuel particles. We hereby quantify the impact of SiC grain size and irradiation on Ag release and improve Bison's predictions.

8:20 AM  
High Temperature Zirconium Alloys by Titanium Analogy: Johan Pauli Magnussen1; Helen Swan2; Alexander J. Knowles1; 1University of Birmingham; 2National Nuclear Laboratory
    The use of conventional zirconium alloys at temperatures >400°C is restricted by their poor creep and oxidation resistance. This limits the consideration of zirconium alloys for fusion and Generation IV fission plant designs operating at 500°C–1000°C. Zirconium has a physical metallurgy similar to titanium, which has seen alloying advances allowing application temperatures ~600°C. A set of alloys in the Zr-Al-Sn system, designed by analogy to near-alpha titanium alloys, were synthesised by arc melting, and processed in a sequence of homogenisation, cold rolling, recrystallisation, and ageing treatments. Electron and optical microscopy combined with diffraction showed a refined Widmanstätten microstructure reinforced by Zr₃Al precipitates, with microstructures differing with ageing times. Deformation testing using three-point bending revealed a strengthening effect by Al, but with significant changes to ductility on ageing depending on the evolution of Zr₃Al. The microstructure and properties of these alloys suggest they are promising candidates for further development.

8:40 AM  Invited
Convolutional Neural Networks Screening Radiation-resistant High Entropy Alloys: Penghui Cao1; 1University of California, Irvine
    The emergent multi-principal element alloys (MPEAs), commonly known as high entropy alloys, provide a vast compositional space to search for radiation-resistant materials for advanced nuclear reactor application. However, how to efficiently identify optimal compositions is a grand challenge. This talk will present a convolutional neural network model that can accurately and efficiently predict path-dependent defect migration energy barriers—the critical parameters to radiation defect evolution and growth in MPEAs. The success of the machine learning model makes it promise to develop a database of defect diffusion barriers for different multicomponent alloy systems, which would accelerate alloy screening for the discovery of new compositions with desirable radiation performance.

9:10 AM  
Defect Dynamics and Far-from-Equilibrium Microstructure Evolution in Concentrated Alloys: Yanwen Zhang1; Matheus Tunes2; Stephen Donnelly3; Philip Rack4; William Weber4; 1Oak Ridge National Laboratory; 2Los Alamos National Laboratory; 3University of Huddersfield; 4University of Tennessee
     In a radiation environment, energetic particles carry substantial momentum. Significant energy loss to electrons and nuclei induces far-from-equilibrium athermal processes.1 Concentrated solid-solution alloys (CSAs) exhibit distinct chemical disorder that affects energy dissipation and defect evolution processes.2 Compared with thermally-driven events, athermally-driven processes are generally weakly dependent on or independent of temperature. The athermal processes can be largely considered as a far-from-equilibrium state (localized resolidification after the ballistic phase as the shockwave transitions to a sonic velocity) followed by a close-to-equilibrium state (the electron, phonon, and magnon contributions to heat conduction during the kinetic phase).1,2 In this presentation, early-stage defect production and damage accumulation from radiation-induced nonequilibrium processes in CSAs are discussed. Late-stage microstructural evolution when damage accumulates is deliberated in comparison of both chemically simple and complex CSAs. References 1. Applied Physics Review, 7 (2020) 041307. 2. Chemical Reviews 122 (2022) 789–829.

9:30 AM  Invited
Atomistic Calculations and Theoretical Formulations of Thermal Vacancies in Complex Concentrated Alloys: Yongfeng Zhang1; Anus Manzoor1; Sean Masengale1; Dilpuneet Aidhy2; 1University of Wisconsin; 2University of Wyoming
    Complex concentrated alloys (CCAs) are promising candidates for structural applications in future nuclear reactors for their superior resistance to irradiation damage. Understanding their irradiation behavior requires understanding the properties of basic defects such as vacancies. In this talk, atomistic methods such as density functional theory, molecular dynamics, and lattice Monte Carlo are used in conjunction with statistical mechanics theories for predicting thermal vacancy concentration and its spatial distribution. In simple metals, vacancy is a lattice imperfection with a uniform formation energy and a homogeneous distribution in bulk. In contrast, in CCAs, vacancy has preferential chemical environments in the atomic scale. The vacancy formation energy exhibits both a probability distribution and a spatial distribution dependent on the chemical ordering in bulk alloy. The probability distribution is critical for estimating the thermal vacancy concentration, and the spatial distribution is critical for elucidating the diffusion path, particularly in CCAs with short-range order.

10:00 AM Break

10:20 AM  Invited
Novel Refractory High Entropy Alloys for Applications in Extreme Environments: Osman El-Atwani1; Saryu Fensin1; Duc Nguyen2; Jan Wrobel3; Enrique Martinez4; 1Los Alamos National Laboratory; 2United Kingdom Atomic Energy Authority; 3Warsaw University of Technology; 4Clemson University
    In the quest of new materials that can withstand severe irradiation and mechanical extremes for advanced applications (eg. fission reactors, fusion devices, space applications, etc.), design, prediction and control of advanced materials beyond current material designs become a paramount goal. W-based refractory high entropy alloys (HEAs) have been recently developed in the context of high temperature applications. Here, we present novel W-based refractory nanocrystalline and coarse grained HEAs and their performance to extreme environments. In-situ TEM thermal stability experiments, mechanical properties and irradiation resistance to single and dual beam irradiations are assessed. The results are elucidated based on theoretical modeling combining ab initio and Monte Carlo techniques. The simulation (CALPHAD, DFT and Cluster Expansion) guided HEAs demonstrated outstanding irradiation resistance and high thermal stability and mechanical properties, establishing a breakthrough in the design of new materials for extreme environments.

10:50 AM  Invited
Microstructural Response of HT-UPS Steel to Thermal Annealing and Neutron Irradiation: Maria Okuniewski1; 1Purdue University
    High temperature – ultrafine precipitate strengthened (HT-UPS) steel is an advanced austenitic steel with micro- and nano-sized precipitates designed to serve as sinks for irradiation-induced defects. This study uniquely investigates the microstructural response of HT-UPS to both thermal annealing and low fluence neutron irradiations before and after the stimulus is applied. Three-dimensional evolution of the grain and precipitate morphologies are studied as a function of dose and annealing time using synchrotron high-energy diffraction microscopy and micro-computed tomography. Whereas the crystallography and chemistry of the precipitate and matrix phases are characterized via synchrotron X-ray diffraction and X-ray absorption spectroscopy.

11:20 AM  
BCC CrAl Thin Film, A Solution for Next-generation High-performance Inert Gas Cooled Nuclear Microreactors: Sumit Bhattacharya1; Yinbin Miao1; Nicolas Stauff1; Claudio Filippone1; Abdellatif Yacout1; 1Argonne National Laboratory
    Next generation high-temperature gas-cooled nuclear microreactors (micro-HTGR), operated in harsh environments at or beyond 700 oC under radiation and thermal cycling conditions, demands rapid turnaround development of high-performance materials for prompt deployment of reactor technologies with higher efficiencies to reduce spent fuel production and carbon emissions. Given the considerable time and cost needed to develop/qualify new structural materials for advanced reactors, advanced surface modifications applied to qualified nuclear materials has been regarded as an optimal approach to enhance micro-HTGR performance. This report provides the results of a surface modification technology represented by a thin film developed with CrAl (BCC phase) alloy uniquely suited for high-temperature applications due to its; (a) exceptional thermal phase stability at elevated temperatures (~900 oC); (b) immunity from oxidant contaminants typically found in industrial grade inert gas coolants, after exposures to multiple high temperature thermal cycling; and (c) radiation tolerance, under high temperature thermal cycling conditions.

11:40 AM  
In Situ Dual Ion Irradiation of Additively Manufactured Reduced Activation Ferritic-martensitic Steels: Robert Renfrow1; T.M. Kelsy Green1; Priyam Patki2; Wei-Ying Chen3; Christopher Field4; Kevin Field1; 1University of Michigan; 2Intel Corporation; 3Argonne National Laboratory; 4Theia Scientific, LLC
    Additively manufactured (AM) reduced activation ferritic-martensitic (RAFM) steels are attractive materials for structural components in fusion reactors. However, an existing knowledge gap for AM-RAFM steels is the role of helium in the microstructural evolution under irradiation since fusion reactors will produce a helium concentration per dpa different than any fission irradiation spectrum. Therefore, helium’s role in the dynamic behavior of dislocation loop formation and growth must be determined to understand the fundamental mechanisms of irradiation behavior in novel AM-RAFM steels. To observe these helium-induced effects, in situ dual-ion (Kr+He) irradiations were conducted at the IVEM-Tandem facility at ANL. Quantification of dislocation loop size and density was performed in real-time and post-acquisition using machine learning techniques during irradiation and by human quantification at discrete irradiation steps. It was concluded that the time to reach saturation of loop formation decreases with increasing helium content when all other irradiation factors are held constant.