Computational Materials Science and Engineering of Materials in Nuclear Reactors: Multiscale Modeling I
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Dilpuneet Aidhy, Clemson University; Michael Tonks, University of Florida; Mahmood Mamivand; Giovanni Bonny, Belgian Nuclear Research Center
Thursday 8:30 AM
February 27, 2020
Room: Theater A-9
Location: San Diego Convention Ctr
Session Chair: Alfredo Correa, LLNL; Dilpuneet Aidhy, University of Wyoming
8:30 AM Invited
Electron-phonon Coupling Effects in Ion Irradiation of Metallic Systems: Eva Zarkadoula1; German Samolyuk1; William Weber2; 1Oak Ridge National Laboratory; 2University of Tennessee
In ion irradiation, energy from the projectiles is transferred both to the nuclei and to the electrons of the material. While it is known that the nuclear energy loss results in defects and defect clusters, the effects of the electronic energy loss are not well understood. Using the two-temperature model in molecular dynamics simulations of cascades in nickel and nickel-based alloys, the effects of the electron-phonon interactions in the energy dissipation and damage production are investigated. Our results show that the local energy exchange between the atomic and electronic subsystems affects the number of surviving defects, as well as the size of the defect clusters. Including the electronic effects in molecular dynamics simulations of cascades is a better approach to the processes that take place during high energy irradiation, as it considers both energy loss mechanisms.
9:10 AM
First Principles Modeling of Ion Ranges in Self-irradiated Tungsten: Andrea Sand1; Rafi Ullah2; Alfredo Correa2; 1University of Helsinki; 2Lawrence Livermore National Laboratory
We have calculated channeling ion ranges for tungsten by simulating ion trajectories taking into account both the nuclear and the electronic stopping power. The electronic stopping power of self- ion irradiated tungsten is obtained from first-principles time-dependent density functional theory (TDDFT). Although the TDDFT calculations predict a lower stopping power than SRIM by a factor of three, our results [1] show good agreement in a direct comparison with ion range experiments. These results demonstrate the validity of the TDDFT method for determining electronic energy losses of heavy projectiles, and in turn its viability for the study of radiation damage. [1] A. E. Sand, R. Ullah, and A. A. Correa, Heavy ion ranges from first-principles electron dynamics, npj Com- putational Materials 5, 43 (2019).*Prepared by LLNL under Contract DE-AC52-07NA27344. The work was supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division.
9:30 AM
First-principles Cluster Expansion Study of Fe and Mo Effects on Atomic Ordering in Ni-Cr Alloys: Jia-Hong Ke1; Julie D. Tucker1; 1Oregon State University
The development of atomic ordering in nickel-chromium alloys is of great technological interest but the non-dilute solute effect on the transformation is not well understood due to complex solute synergies. This research utilizes first-principles density functional theory (DFT), cluster expansion, and Monte Carlo simulation to explore the role of Fe and Mo in phase stability of the ordered structure. A quarternary Ni-Cr-Fe-Mo cluster expansion is constructed and the effective cluster interactions are derived based of the dataset of DFT energetics. The results show that non-dilute Mo stabilizes Ni2Cr ordering and raises the order-disorder transition temperature, while Fe produces the opposite effect. The predicted transition temperature is consistent with previous experiments. In the Monte Carlo simulation, we further investigate the preferential occupation of Fe and Mo atoms in the Ni2Cr sublattice. These results help gauge the risk of industrial alloys developing atomic ordering which increases strength but degrades ductility and toughness.
9:50 AM
Modeling the Fracture of Zirconium at an Atomic Level and Analyzing the Effects of Temperature and Strain Rate on the Deformation Mechanisms: Vlad Podgurschi1; Kailan Luo1; Mark Wenman1; 1Imperial College London
Molecular dynamics simulations of single crystal zirconium fracture were performed in order to study the deformation mechanisms active on the basal and prismatic planes. In addition, the effects of temperature (0 K, 150 K and 300 K) and strain rate were investigated. The crack tip orientation was found to strongly affect the plasticity of the crack tip with significant deformation taking place on the basal plane and little plasticity seen on the prismatic plane. The basal crack propagated easier than the prismatic crack. Both temperature and strain rate were observed to affect the {11-21}<-1-126> type twinning and dislocation emission at a basal crack tip. For the prismatic crack tip the primary deformation mechanism was the emission of 1/3<1-210> dislocations at 60˚ to the crack plane and was observed to be temperature independent.
10:10 AM Break
10:30 AM Invited
First Principles Modelling of the Role of Electrons in Collision Cascades in Solids: Artur Tamm1; Magdalena Caro2; A. Caro3; Alfredo Correa1; 1Lawrence Livermore National Laboratory; 2Virginia Tech; 3George Washington University
We present a model for the role of electrons in collision cascades in solids in which the coupling between ions and electrons is calculated using first-principles models and introduced into the classical ion equations of motion using our modified Langevin dynamics. This model gives a full picture of the entire collision process, from the ballistic to the thermal phases of a cascade, giving a detailed representation of the energy exchange between ions and electrons until their final thermalization, removing in this way some ad hoc assumptions used in the state-of-the-art two-temperature model. We use the model in ion-solid interactions over a wide range of energies in concentrated solid-solution fcc alloys of the 3d transition metals Ni, Co, Fe, and Cr and collision cascades. *Prepared by LLNL under Contract DE-AC52-07NA27344. The work was supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division.
11:10 AM
A Machine Learning Approach to Thermal Conductivity Modelling of Irradiated Nuclear Fuels: Elizabeth Kautz1; Alexander Hagen1; Jesse Johns1; Douglas Burkes1; 1Pacific Northwest National Laboratory - PNNL
A deep neural network was developed for the purpose of predicting thermal conductivity with a case study performed on neutron irradiated nuclear fuel. Traditional thermal conductivity modeling approaches rely on existing theoretical frameworks that describe known, relevant phenomena that govern the microstructural evolution processes during irradiation (e.g. recrystallization, and pore size, distribution and morphology). Current empirical modeling approaches, however, do not represent all irradiation test data well. Here, we develop a machine learning approach to thermal conductivity modeling that does not require a priori knowledge of a specific material microstructure and system of interest. Our approach allows researchers to probe dependency of thermal conductivity on a variety of reactor operating and material conditions. Results indicate our model generalizes well to never before seen data, and thus use of deep learning methods for material property predictions from limited, historic irradiation test data is a viable approach.
11:30 AM
Phase-field Simulation of Intergranular Fission Gas Bubble Growth in Uranium Silicide: Larry Aagesen1; David Andersson2; Benjamin Beeler1; Michael Cooper2; Kyle Gamble1; Yinbin Miao3; Giovanni Pastore1; Cody Permann1; Michael Tonks4; 1Idaho National Laboratory; 2Los Alamos National Laboratory; 3Argonne National Laboratory; 4University of Florida
Uranium silicide (U3Si2) is considered a promising candidate for use as an accident-tolerant fuel (ATF) in nuclear reactors due to its high thermal conductivity compared with UO2. However, its swelling and fission gas release behavior have not yet been thoroughly characterized. In the absence of experimental data, a multi-scale model of U3Si2 fuel performance has been developed using Idaho National Laboratory’s Bison code. The rate of percolation of intergranular gas bubbles has a significant influence on the model’s predictions of swelling and gas release. A phase-field model in Idaho National Laboratory’s Marmot code was used to simulate the rate of percolation of intergranular bubbles. The phase-field model is based on a grand-potential formulation that considers monovacancies and Xe atoms as defect species, and was parameterized using lower-length scale calculations. The phase-field simulation results were used to parameterize the engineering-scale Bison model.