A research team in Nicola Marzari's MARVEL laboratory at EPFL has turned to theory and computational methods to address this question. Their recent study, published in *PRX Energy*, presents a large-scale screening process designed to identify the most promising plasma-facing materials for fusion applications.
"A realistic simulation of the dynamics at the plasma-material interface would require simulating thousands of atoms over several milliseconds, which isn't feasible with conventional computational power," explained Andrea Fedrigucci, PhD student and first author of the paper. "Instead, we selected specific properties essential for a plasma-facing material and used them to evaluate potential candidates for the divertor."
The team initially consulted the Pauling file database, analyzing a vast array of inorganic crystal structures to identify those capable of surviving the reactor's intense heat. Key properties such as thermal capacity, thermal conductivity, melting temperature, and density helped narrow the selection. They then assessed each material's maximum thickness before melting, ranking materials based on their ability to maintain surface integrity under heat stress. For materials lacking comprehensive thickness data, they employed a Pareto optimization approach to rank based on other critical properties.
This comprehensive screening produced a preliminary shortlist of 71 materials. From here, a manual review became necessary. "I examined literature on each candidate to see if any had already been tested or if they exhibited characteristics that would limit their effectiveness in a fusion reactor, such as susceptibility to erosion or thermal degradation," said Fedrigucci. This review ruled out some materials previously suggested for fusion applications, including high-entropy alloys.
After eliminating less viable options, 21 materials remained. The researchers then applied density functional theory (DFT) to analyze two critical properties for fusion: surface binding energy, indicating resistance to erosion, and formation energy of a hydrogen interstitial, which reflects tritium solubility. "If a divertor material undergoes excessive erosion, the dispersed atoms cool the plasma, reducing efficiency," Fedrigucci noted. "Additionally, a material that reacts with tritium could reduce tritium availability for fusion, creating a safety hazard by raising tritium inventory levels."
Ultimately, the final list included established candidates like tungsten (in both metallic and carbide forms), diamond, graphite, boron nitride, and several transition metals, including molybdenum, tantalum, and rhenium. Notably, new contenders emerged as well, including a rare phase of tantalum nitride and some boron- and nitrogen-based ceramics that had yet to be tested for this application.
Looking ahead, the MARVEL team intends to incorporate neural network models to simulate material interactions with neutrons, a factor currently beyond their computational reach, which could further refine their search for ideal fusion reactor materials.
Research Report:Comprehensive Screening of Plasma-Facing Materials for Nuclear Fusion
Related Links
National Centre of Competence in Research (NCCR) MARVEL
Powering The World in the 21st Century at Energy-Daily.com
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