Commercial fusion power, often compared to harnessing the sun’s energy, has the potential to provide a sustainable and virtually limitless energy source. However, significant scientific and engineering challenges must be addressed before fusion power can become a practical reality. Among the most pressing obstacles are the materials required to withstand the extreme conditions inside a fusion reactor. Researchers from the U.S. Department of Energy’s (DOE) Ames National Laboratory and Iowa State University are leading efforts to tackle these material challenges, working under the DOE’s Advanced Research Projects Agency-Energy (ARPA-E) program, Creating Hardened And Durable fusion first Wall Incorporating Centralized Knowledge (CHADWICK).
The CHADWICK program, which recently selected 13 projects, focuses on developing materials for the first wall of a fusion reactor. This structure surrounds the fusion reaction and endures the harshest conditions, including extreme temperatures, irradiation, and magnetic fields. Ames Lab leads one of these projects and collaborates with Iowa State University on another led by Pacific Northwest National Laboratory (PNNL).
Nicolas Argibay, a scientist at Ames Lab and lead of one project, explained that containing the plasma core — a miniature sun-like environment — is a central challenge in fusion power. The first wall, which surrounds the plasma, must be composed of materials capable of withstanding these extreme conditions while efficiently transferring heat for electricity generation. The first wall consists of two material layers: one closest to the plasma and magnetic fields and another that facilitates energy transfer.
For safe reactor maintenance, the inner layer must be structurally robust, resistant to cracking and erosion, and have low post-irradiation radioactivity. Argibay’s team focuses on this inner layer, using tungsten, which has the highest melting point of any element except carbon. “It is hard to make and manage these materials,” Argibay said. “We’re using tungsten as a major constituent, and, with the exception of some forms of carbon, like diamond, that’s the highest melting temperature element on the periodic table.”
Recent investments by ARPA-E and Ames Lab have equipped researchers with advanced tools for processing and testing refractory materials, which have extremely high melting points. Argibay’s lab now has a modular platform for creating refractory materials, including tungsten alloys, and will soon add systems for producing these materials at both lab and pilot scales. Ames Lab also possesses one of the few commercial testers in the U.S. capable of measuring the mechanical properties of alloys at temperatures up to 1500° C (2732° F), a critical capability for fusion research.
Jordan Tiarks, another Ames Lab scientist working on the PNNL-led project, is focused on the structural material for the first wall. His team is leveraging Ames Lab’s expertise in gas atomization and powder metallurgy to develop oxide dispersion-strengthened (ODS) steels and vanadium-based alloys. ODS steels, which contain ceramic nanoparticles, offer enhanced mechanical properties and irradiation resistance. Tiarks’ team is adapting these lessons to vanadium-based alloys, which are better suited for fusion environments due to their compatibility with magnetic fields.
However, vanadium presents unique challenges. It has a higher melting point and is more reactive than steel, requiring a specialized process called free-fall gas atomization to create powders. “Powders are reactive. If you aerosolize them, they like to explode!” Tiarks explained. “A lot of the research we’ve done in Ames Lab is actually figuring out how to passivate these powders so you can handle them safely, so they won’t further react, but without degrading too much of the performance of those powders by adding too much oxygen.”
Sid Pathak, an assistant professor at Iowa State University, leads the testing of material samples for the second layer of the first wall. His team uses ion irradiation to simulate the effects of radiation on materials, a process that accelerates testing by mimicking years of damage in hours. “Ion irradiation is a technique where you radiate [the material] with ions instead of neutrons. That can be done in a matter of hours,” Pathak said. “Also, the material does not become radioactive after ion irradiation so that you can handle it much more easily.”
Despite the progress, significant challenges remain. The materials must be tested at microscopic scales, as ion irradiation only penetrates one or two micrometers into the material. Pathak’s lab at Iowa State is equipped with specialized tools for these micro-scale analyses.
The researchers acknowledge the complexity of the task but remain optimistic about the potential impact of their work. “The pathway to commercial nuclear fusion power has some of the greatest technical challenges of our day but also has the potential for one of the greatest payoffs—harnessing the power of the sun to produce abundant, clean energy,” said Tiarks. “It’s incredibly exciting to be able to have a tiny role in solving that greater problem.”
Argibay echoed this sentiment, emphasizing the unique role of national labs in tackling such ambitious challenges. “I’m very excited at the prospect that we are kind of in uncharted water. So there is an opportunity for Ames to demonstrate why we’re here, why we should continue to fund and increase funding for national labs like ours, and why we are going to tackle some things that most companies and other national labs just can’t or aren’t,” he said. “We hope to be part of this next generation of solving fusion energy for the grid.”
By addressing these material and engineering challenges, the researchers aim to bring commercial fusion power closer to reality, offering a promising solution for sustainable energy production.
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