Transmutation Effects in Fusion Reactor Materials: Critical Challenges & Path Forward: Radiation Damage Characterization, Modeling & Alloy Design I
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Arunodaya Bhattacharya, Oak Ridge National Laboratory; Steven Zinkle, University of Tennessee; Philip Edmondson, The University Of Manchester; Aurelie Gentils, Université Paris-Saclay; David Sprouster, Stony Brook University; Takashi Nozawa, National Institutes for Quantum and Radiological Science and Technology (QST); Martin Freer, University of Birmingham
Thursday 8:30 AM
March 23, 2023
Room: 27B
Location: SDCC
Session Chair: Lance Snead, Stony Brook University; Aurelie Gentils, University of Paris-Saclay, CNRS
8:30 AM Invited
Characterizing Transmutation Products in Materials via STEM and Machine Learning: Chad Parish1; 1Oak Ridge National Laboratory
Both fission and fusion materials will suffer significant transmutation of atoms under high-energy neutron irradiation. Here at ORNL, we are exploring scanning/transmission electron microscopy (STEM)-based methods to characterize and quantify these microstructural processes. In particular, STEM is a powerful tool for nanometer-scale characterization of elemental species present in a material. We are using a combination of high-throughput STEM X-ray spectrum imaging with automated mapping and machine learning to explore large volumes of material with higher statistical confidence. Examples from tungsten and fusion steels, irradiated in the High Flux Isotope Reactor, will be presented with discussions of strengths and limitations of the methods, and an eye to improvements for the future Fusion Prototypic Neutron Source (FPNS) transmutation science era, as well as synergies with fission materials studies.
9:10 AM
Suppression of Rhenium and Osmium Production in Tungsten-based Materials for Fusion Energy: Mark Anderton1; Matthew Lloyd2; Thomas Davis1; 1Oxford Sigma Ltd; 2Singapore University of Technology and Design
Tungsten transmutes to rhenium and osmium under neutron irradiation. Recent research indicates that transmutation effects in tungsten dominate the degradation of its mechanical and thermophysical properties. Oxford Sigma is developing technology that suppresses the rhenium and osmium production via enrichment of selective tungsten isotopes in order to improve the neutron radiation damage resistance. The displacement of tungsten-186 suppresses the production of rhenium and osmium isotopes via transmutation. Oxford Sigma’s isotopically enriched tungsten mainly transmutes to tantalum, an element that is soluble within the matrix. This talk will discuss the latest project development on isotopically enriched tungsten [1]. Modelling work, such as inventory modelling and neutronics, will be presented. In particular, the possibility of improving the mechanical and thermal properties will be discussed. Moreover, this talk will discuss a pathway for commercialising such a technology to accelerate the development of fusion energy. [1] Davis, T, and Lloyd, M, J. Patent GB202105750D0
9:30 AM
Investigation of High Temperature He Embrittlement Effects in High Performance Nickel-based Alloys: Zehui Qi1; Steven Zinkle1; 1University of Tennessee, Knoxville
For fusion and Gen IV reactor concepts operating at high temperatures and doses, high temperature He embrittlement (HTHE) might be the lifetime limit mechanism for potential structural materials. It is well accepted that tensile stress can dramatically enhance HTHE. However, limited creep test data during irradiation are available due to its drawback of high cost and long experimental time. In this context, an innovative specimen fixture was designed to provide tensile stress from zero to ~200 MPa during ion irradiation. We performed 4.5 MeV He^(2+) irradiations on 316 stainless steel, Fe-9Cr and three high-performance commercial Ni-based alloys at 650℃ and 750℃ with peak implanted He concentration of 200 appm for different stresses and He implantation rates. The size and number density of bubbles and cavities (matrix and grain boundary) were characterized by conventional TEM to quantify bubble behavior versus applied stress and He implantation rate for different matrix precipitate distributions.
9:50 AM
Machine Learning Generation of Trajectories for Accurate Modeling Plasma Material Interactions: Osetsky Yury1; German Samolyuk1; Eva Zarkadoula1; Markus Eisenbach1; Cornwall Lau1; Juergen Rapp1; 1Oak Ridge National Laboratory
The Materials Plasma Exposure eXperiment (MPEX) is a device for studying fusion reactor-relevant plasma-materials interactions (PMI). A corresponding MPEX digital twin aims to model the main processes of MPEX, including the PMI’s that ultimately define the degradation of the target material. Traditionally, PMI are considered within the binary collision approximation (BCA) implemented in various codes such as SRIM. These codes are not able to model the realistic trajectories of ions in materials depending on crystallography, temperature, and microstructure. To address this limitation, we developed a machine learning approach to model ion trajectories using classical and ab initio molecular dynamics (MD). First, we demonstrated that the full MD modeling results in different trajectories and penetration depths. Second, we have generated a database that can be used to reproduce PMI for MPEX-relevant ions and their energy and velocity spectra. The developed approach is applicable to different target and plasma compositions.
10:10 AM Break
10:30 AM Invited
Magic Numbers on the Shape of Voids Formed by Electron Irradiation in Aluminium: Estelle Meslin1; Camille Jacquelin1; C.-C. Fu1; Maylise Nastar1; 1CEA
In-situ irradiation effects in aluminium, a low-mass material allowing the direct formation of defects by electron irradiation within an HRTEM, will be presented. We obtained a strong effect of hydrogen partial pressure on the kinetics of formation of cavities and dislocation loops and developed a multi-scale modeling of the effects of finite size and network discretization on DFT based-equilibrium shapes of cavities. Measurements of cavity shape dispersion during its growth and shrinkage showed a dominant effet of magic numbers, fixed by geometry and network frustration. Based on a thermodynamic model and a fine experimental characterization of the density and the size distribution of the cavities, we propose a nucleation model of cavities under irradiation. Finally, we discuss the effect of hydrogen on the stability of vacancy-hydrogen clusters and on the kinetic of cavity nucleation.
11:10 AM
No Ball Milling Needed: Revamping Fabrication Route of ODS Steel Plate with Cold Spray and Friction Stir Processing: Dalong Zhang1; Jens Darsell1; Kenneth Ross1; Glenn Grant1; Iver Anderson2; Jia Liu1; Xiaolong Ma1; Danny Edwards1; Wahyu Setyawan1; 1Pacific Northwest National Laboratory; 2Ames Laboratory
Oxide dispersion strengthened (ODS) steels are promising structural materials for future fusion reactors. The state-of-the-art fabrication route for ODS steel plate involves production of powder by gas atomization, ball milling, powder vacuum canning, hot isostatic pressing, hot cross rolling, cold rolling, with annealing steps often required in-between rolling steps. This route is time consuming, expensive, difficult to scale up, and extremely delicate as cracks can develop and the plate can “bend out of shape” during the laborious rolling process. Instead, we have demonstrated a new route involving much less steps: production of precursor ODS steel powder with gas atomization reaction synthesis (GARS) without the need of ball milling, direct cold spray of GARS powder onto a ferritic-martensitic P92 steel substrate to form plate, friction stir processing of the plate to further refine microstructure and disperse Y/Ti/O species, and final heat treatment as needed to further improve nano-oxide characteristics and properties.