Accelerated Discovery and Qualification of Nuclear Materials for Energy Applications: Multiscale, Physics Based Modeling of Nuclear Materials
Sponsored by: TMS Structural Materials Division, TMS Materials Processing and Manufacturing Division, TMS: Integrated Computational Materials Engineering Committee, TMS: Nuclear Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Yongfeng Zhang, University of Wisconsin; Adrien Couet, University of Wisconsin-Madison; Michael Tonks, University of Florida; Jeffery Aguiar, Lockheed Martin; Andrea Jokisaari, Idaho National Laboratory; Karim Ahmed, Texas A&M University
Wednesday 2:00 PM
March 17, 2021
Room: RM 48
Location: TMS2021 Virtual
Session Chair: Benjamin Beeler, North Carolina State University ; Shijun Zhao, City University of Hong Kong
2:00 PM Invited
Overview of Advanced Fuels and Materials R&D within the US DOE-NE NEAMS Program: Chris Stanek1; 1Los Alamos National Laboratory
The U.S. Department of Energy Office of Nuclear Energy program NEAMS (Nuclear Energy Advanced Modeling and Simulation) is tasked with developing predictive computer methods and performing modeling and simulation research for the analysis and design of nuclear reactors (both LWRs and non-LWRs). A key element of the NEAMS program since its inception over a decade ago is multiscale nuclear fuel performance. Recently, a similar approach has been applied to structural materials, which is motivated by the need to understand the behavior of components in complex environments present in advanced reactors. In this presentation, an overview of recent activities in the NEAMS program in the areas of fuel performance and structural materials modeling will be presented. In particular, this overview will highlight examples that illustrate how such simulation approaches can be used to accelerate the discovery and qualification of materials for application in LWRs and non-LWRs.
2:30 PM
Constructing Multi-component Diffusion under Irradiation in U-Mo Alloys: Benjamin Beeler1; Bei Ye2; Yipeng Gao3; Shenyang Hu4; 1North Carolina State University; 2Argonne National Laboratory; 3Idaho National Laboratory; 4Pacific Northwest National Laboratory
Under the United States High-Performance Research Reactor (HPRR) program, a number of research reactors are planned to undergo a conversion to U-Mo monolithic fuel. The accurate prediction of fuel evolution under irradiation requires implementation of correct thermodynamic and kinetic properties into fuel performance modeling. One such property where there exists incomplete data is the diffusion of relevant species under irradiation. Fuel performance swelling predictions rely on an accurate representation of diffusion in order to determine the rate of fission gas swelling and local microstructural evolution. In this work, molecular dynamics simulations are combined with rate-theory calculations to determine the radiation-enhanced diffusion of U and Mo as a function of temperature and fission rate. In combination with previous studies on intrinsic diffusion and radiation-driven diffusion in U-Mo alloys, this study completes the multi-component diffusional picture for the U-Mo system.
2:50 PM
Effective Bias for Interstitial Clusters to Cavities in BCC Fe: Yuhao Wang1; Fei Gao1; Brian Wirth2; 1University of Michigan - Ann Arbor; 2University of Tennessee, Knoxville
Atomistic modeling is used to study the cavity bias for point defects and defect clusters. The results will provide important atomic inputs for cluster dynamics simulation of microstructural evolution. Statics calculations found that 7-interstitial and vacancy clusters have much larger interaction radii than single and di-interstitials and vacancies, and the bias for 7-interstitial clusters over 7-vacancy clusters is about 45% to 65%, on average, stronger than that for single and di-interstitials over single and di-vacancies at temperatures from 25 K to 1811 K. Dynamics calculation indicates that 2, 3 and 4-interstitial clusters behave as 3-dimensional diffusers that are easily absorbed by a vacancy cluster after multiple rotations. However, 5, 6 and 7-interstitial clusters diffuse one-dimensionally without rotations at temperatures below 1000 K for simulation time up to 5 ns. A specific homogenization method was established to describe the capture volume of the interstitial clusters to mimic its one-dimensional diffusion behavior.
3:10 PM
Microscale Measurement of Elastic Constants in Ceramics Using Picosecond Ultrasonics for High Throughput Characterization and Atomic Model Validations: Yuzhou Wang1; David Hurley2; Zilong Hua2; Amey Khanolkar2; Cody Dennett2; Marat Khafizov1; 1Ohio State University; 2Idaho National Laboratory
Accurate measurement of property and microstructure on microscale enables high throughput characterization that is important for accelerated development and qualification of materials. Laser-based optical spectroscopies have already demonstrated high throughput capability for a range of technological and medical applications. In this work, picosecond ultrasonics was employed to measure the components of the elastic stiffness tensor of two model oxide nuclear fuel systems, thoria and ceria. The technique relies on optical method to generate and detect ultrasonic waves. Three independent elastic constants of cubic materials could be obtained from a single measurement on a single crystal or a grain in polycrystalline materials. The selected grain orientation ensures generation and detection of all ultrasonic wave modes. We further demonstrate that temperature dependent measurement allows investigation of crystal anharmonicity. This technique can be conveniently integrated into an all-optical setup to study irradiation damages for nuclear materials screening.
3:30 PM
Effect of Distributed Gas Bubbles on Elastic-plastic Deformation Behavior in Polycrystalline UMo: Shenyang Hu1; Benjamin Beeler2; Douglas Burkes1; 1Pacific Northwest National Laboratory; 2North Carolina State University
The macroscale fuel performance model requires constitutive equations that describe elastic-plastic properties, swelling and creep rates as a function of fission conditions and fuel microstructures. In this work, we leverage the existing computational capability of gas bubble evolution, radiation defect accumulation and elastic-plastic deformation to develop a physics-based model of deformation in irradiated UMo fuels. The crystal plasticity theory is used to describe the inhomogeneous and anisotropic deformation in the polycrystalline UMo with distributed gas bubbles. Based on simulations and experiments, a set of gas bubble structures of different size, density and internal pressure were constructed. The effect of gas bubble structure on elastic-plastic deformation under different stresses were simulated. The constitutive equation of elastic-plastic deformation used in fuel performance modeling in literature was assessed by comparing the predicted elastic-plastic properties. The extension of the model to simulate creep deformation will be discussed in the talk.
3:50 PM
Molecular Dynamics Study of Cascade Overlap Effects in FCC Ni: Samuel Morris1; Brian Wirth1; 1University of Tennessee-Knoxville
Neutron or self-ion irradiation of Ni-base FCC alloys leads to nucleation of immobile Frank dislocation loops. With increasing dose, cascade overlap may play an important role in the microstructural evolution of these alloys. We use molecular dynamics to simulate cascade overlap with existing defects in FCC Ni at various geometries and cascade energies. We study cascade overlap with interstitial and vacancy Frank loops, as well as cavities. We also simulate cascades in defect-free Ni as a benchmark to assess how cascade overlap affects primary damage formation. We find that existing defects may shrink, change Burgers vector, or possibly recombine with in-cascade point defects and subsequently nucleate one or more new defects following cascade quench. However, interstitial Frank loops may grow if overlapped by the interstitial-rich cascade periphery, likely due to loops acting as biased sinks for interstitials. This work should inform multiscale modeling of high-dose irradiation of Ni-base alloys.