Materials Systems for the Future of Fusion Energy: Cross-cutting Experiments and Fusion Materials Perspectives
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee, TMS: Additive Manufacturing Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Jason Trelewicz, Stony Brook University; Kevin Field, University of Michigan; Takaaki Koyanagi, Oak Ridge National Laboratory; Yuanyuan Zhu, University Of Connecticut; Dalong Zhang, Pacific Northwest National Laboratory
Tuesday 8:00 AM
March 1, 2022
Room: 203A
Location: Anaheim Convention Center
Session Chair: Yuanyuan Zhu, University Of Connecticut; Jason Trelewicz, Stony Brook University
8:00 AM
In-situ Thermal Diffusivity Recovery and Defect Annealing Kinetics in Self-ion Implanted Tungsten Using Transient Grating Spectroscopy: Mohamed Abdallah Reza1; Hongbing Yu2; Kenichiro Mizohata3; Felix Hofmann1; 1University of Oxford; 2Canadian Nuclear Laboratories; 3University of Helsinki
Irradiation damage alters the properties of tungsten, the main candidate material for fusion reactor armor. Using transient grating spectroscopy with in-situ annealing, we study the recovery of thermal diffusivity in self-ion implanted tungsten up to 800C for doses from 0.00032 to 3.2 displacements per atom (dpa). Room temperature thermal diffusivity recovers from ~45% to 75% of the pristine value for the highest damage level. Using a kinetic theory model we interpret this recovery in terms of annealing of irradiation-induced defects. Our results show a large removal of defects at ~350C, consistent with the temperatures for mono-vacancy mobility in tungsten. This suggests that the small point defects, invisible to TEM, are the main contributors to thermal diffusivity degradation in room-temperature-irradiated tungsten. The defect recovery estimates also agreed well with TEM annealing experiments. These new results suggest that annealing at relatively modest temperatures may be used to reduce irradiation-induced thermal diffusivity degradation.
8:20 AM
Direct Visualization of Tungsten Oxidation by In-situ Environmental TEM: Maanas Togaru1; Rajat Sainju1; Lichun Zhang1; Weilin Jiang2; Yuanyuan Zhu1; 1University of Connecticut; 2Pacific Northwest National Laboratory
With a view to air ingress accidents and future DEMO PFM safety, engineering tungsten with enhanced oxidation resistance has attracted increasing attention. Here, in situ environmental TEM (ETEM) was applied, for the first time, to investigate the thermal oxidation of polycrystalline tungsten in real-time. In-situ ETEM captured the genuine tungsten oxide phases and stress states during oxidation. We found that oxide scales are highly sensitive to tungsten surface orientation, and they change dynamically in the course of oxidation. Interestingly, a highly textured oxide scale evolved into a complex layered microstructure and was partially stable even at 900 oC. Novel in-situ ETEM insights hold a great promise for the understanding of nanoscale tungsten oxidation processes, especially the dynamic structural evolutions that affect oxidation rate, pore formation and passivating layer breakdown, to inform the best strategy for responding to accidents, and to guide the tungsten engineering for improved oxidation resistance
8:40 AM Invited
Paving the Way for a Fusion Pilot Plant: Kathryn Mccarthy1; 1Oak Ridge National Laboratory
Progress on the technical feasibility of fusion energy, together with the world-wide call for carbon-free, sustainable, environmentally friendly sources of energy have put fusion in the spotlight. The recently completed Fusion Energy Sciences Advisory Committee long-range plan for US fusion and the National Academy of Sciences and Engineering fusion energy report point to the readiness and need for a fusion pilot plant around 2040, while clearly identifying gaps that need to be filled to meet that admittedly aggressive date. A key gap that must be filled is the development and qualification of materials that will function reliably (important for both acceptable basic function and economics – essential for a successful pilot plant) in the harsh fusion environment. This talk will focus on progress towards that goal, emphasizing areas urgently needing attention.