Transmutation Effects in Fusion Reactor Materials: Critical Challenges & Path Forward: Helium, Tritium and Hydrogen Effects II
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
Tuesday 2:30 PM
March 21, 2023
Room: 27B
Location: SDCC
Session Chair: Jean Henry, CEA-Saclay, University of Paris-Saclay; Arunodaya Bhattacharya, Oak Ridge National Lab
2:30 PM Keynote
Critical Evaluation of High Temperature Helium Embrittlement Phenomena in Structural Materials: Steven Zinkle1; Zehui Qi1; Arunodaya Bhattacharya2; 1University of Tennessee; 2Oak Ridge National Laboratory
Ductility reductions associated with growth of grain boundary cavities in mechanically strained He-containing materials at high temperatures (HTHE) is widely recognized as a serious issue in reactor structural materials. Extensive HTHE studies have been performed on austenitic stainless steels and provide a good mechanistic understanding of the importance of parameters such as strain rate, test temperature, overall helium content, and He trapping at nanoscale matrix precipitates. Limited experimental studies on ferritic/martensitic steels have generally reported less significant HTHE effects compared to austenitic (face centered cubic, FCC) stainless steels and Ni alloys. Potential causes of this reported difference in HTHE susceptibility between FCC and BCC alloys will be critically assessed, and recommendations for near-term research to objectively evaluate HTHE sensitivity will be outlined. The crucial roles of helium generation per unit time (rather than He/dpa) and performing application-relevant slow strain rate testing for assessing HTHE susceptibility will be discussed.
3:10 PM
The Effects of High-dose He and H Ion Implantation on the Microstructural Development in EUROFER-ODS Steel: Olga Emelyanova1; Aurelie Gentils2; Katia March3; Yuriy Yagodzinskyy4; Vladimir Borodin5; Pavel Dzhumaev6; Pavel Vladimirov7; 1Université Paris-Saclay, CNRS/IN2P3, IJCLab and National Research Nuclear University MEPhI; 2Université Paris-Saclay, CNRS/IN2P3, IJCLab; 3Eyring Materials Center, Arizona State University; 4Aalto University, School of Engineering; 5National Research Nuclear University MEPhI and NRC "Kurchatov Institute"; 6National Research Nuclear University MEPhI; 7Karlsruhe Institute of Technology
Microstructural evolution in ODS-EUROFER steel caused by ion implantation of high doses of helium and hydrogen, both separately and in combination, was studied by conventional TEM supported by EELS and thermal desorption analysis. The observations are consistent with the known trend that oxide nanoparticles are efficient nucleation sites for helium bubbles. However, contribution of bubbles associated with oxide particles to the total swelling is relatively minor as compared bubbles on other structural defects. In contrast to helium, hydrogen has little effect on the overall swelling in all implantation conditions used. However, considerable increase of hydrogen uptake was observed for both helium-free and helium pre-implanted sample of ODS-EUROFER as compared to EUROFER97. The only detectable effects of hydrogen implantation in helium pre-implanted ODS-EUROFER are rounding of facetted bubbles and trapping of hydrogen atoms at cavity walls. A mechanism of hydrogen accumulation at helium bubbles is proposed based on the accumulated data.
3:30 PM Invited
Studies on Transmutation Effects in Reduced Activation Ferritic/Martensitic Steels in Japan: Hiroyasu Tanigawa1; Yoshiyuki Watanabe1; Masami Ando1; Dai Hamaguchi1; Naoyuki Hashimoto2; Shuhei Nogami3; Takashi Nozawa1; 1National Institutes for Quantum Science and Technology; 2Hokkaido University; 3Tohoku University
The effects of helium and hydrogen on swelling and embrittlement, which affect the lifetime of fusion reactor components under DT neutron irradiation environments, have been studied as a part of research on the transmutation effects of reduced activation ferritic steels. Various ion irradiation experiments are the major experimental methods in Japan for studying transmutation effects. Using a focused ion beam (FIB) fabrication system with a micro-sampling system enables detailed microstructural analysis of ion irradiated ferromagnetic RAFM steels. In addition, micro-tensile methods utilizing the FIB sampling system have also made it possible to evaluate the He effect on the tensile properties in a single lath-block microstructure.In this presentation, the results of these experimental studies in Japan will be reviewed together with the results of theoretical simulation studies that attempted to relate the experimental results to the prediction of phenomena under DEMO conditions.
4:10 PM Break
4:30 PM Invited
Modeling the Effect of He/dpa Rate on Microstructural Evolution in Ferritic-martensitic Alloys: Brian Wirth1; 1University of Tennessee
The impact of He/dpa on microstructural evolution in ferritic - martensitic alloys is very pronounced, both in terms of the bubble/cavity population and the distribution of a/2<111> versus a<100> loops. This presentation will review the available data, and then present results from atomistically-informed cluster dynamics modeling of both prismatic loop evolution as well as that of bubbles and cavities across a range of irradiation temperature and He/dpa ratios. Of particular importance in modeling microstructural evolution is the presence of helium, the partitioning of helium between trapping sites, and the time dependence of helium de-trapping. The presentation will conclude with a comparison between the modeling predictions and experimental data, and a summary of outstanding challenges.
5:10 PM
Synergistic Effects between Radiation Damage and H/He Co-Injection on Swelling in Candidate Fusion Structural Materials: Logan Clowers1; Gary Was1; Zhijie Jiao1; 1University of Michigan
The effects of transmutation gasses H/He on the evolution of radiation-induced cavities were investigated in three RAFM steels: F82H, CNA3, and an Fe8Cr2W model alloy. A series of dual beam (Fe2++He2+) and triple beam (Fe2++He2++H+) ion irradiations were performed at 500°C while systematically varying damage level (50, 100, 150 dpa), damage rate (3x10-4, 1x10-3, 3x10-3 dpa/s), and gas injection rate (0/10, 40/10, 80/10 appm/dpa of H/He) to understand the synergisms between H, He and radiation damage. Post-irradiation characterization was done via bright-field TEM and high-angle annular dark field STEM on cross-sectional FIB lamella to determine the effects of single-parameter variations on the cavity microstructure. To understand the mechanisms by which this synergy serves to enhance swelling, 2D EELS maps were taken around cavities to attempt to determine the locations of H and He at these features. Presented results will shed light on the role of hydrogen in increasing cavity growth.