A research team at Penn State is investigating how to implement liquid metals into nuclear fusion reactors through a project supported by the U.S. Department of Energy. Credit: Caleb Craig/Penn State.
Q&A: Could liquid metal be used to contain the power of stars?
An interdisciplinary group including researchers from Penn State is developing plasma-resistant materials for use in fusion reactors
Oct 29, 2025
By Ty Tkacik
UNIVERSITY PARK, Pa. — The same reaction that fuels stars, known as nuclear fusion, could be used to produce a clean, powerful and abundant source of energy, according to the U.S. Department of Energy (DOE), which recently awarded $128 million to seven teams researching how to harness the reaction. The newly announced collaborative program supported by the DOE, known as the Fusion Innovation Research Engine (FIRE) Collaboratives, includes one team featuring researchers at Penn State.
As part of a FIRE project led by the Princeton Plasma Physics Laboratory, researchers at Penn State received more than $1 million to address key challenges in the construction of devices that make nuclear fusion possible.
Xing Wang, assistant professor of nuclear engineering and Penn State institutional principal investigator, and Martin Nieto-Perez, associate teaching professor of nuclear engineering and institutional co-principal investigator, discussed the fusion research and their contributions in the following Q&A.
Q: What is fusion energy, and what are its advantages compared to other forms of energy? What stage of research is it in?
Wang: Fusion energy is created by colliding two nuclei — dense centers of atoms that contain protons and neutrons. This process morphs the nuclei together, forming a heavier nucleus with less mass than the original pair. The mass lost in this reaction is released as extraordinarily powerful and efficient energy, while remaining inherently safe. It has been theorized that this energy may one day serve as the most practical energy source for not just clean energy on Earth, but interstellar travel.
Although commercial fusion has perpetually been regarded as ”50 years away,” recent breakthroughs are raising hopes that viable fusion reactors could be demonstrated within the next 10 to 20 years. Many of the most ambitious projects pursuing this goal are now being led by industry, and it is expected that this industry support will help researchers rapidly progress on the development of this technology.
Q: What makes the construction of a fusion reactor different from a traditional nuclear reactor? How does your work improve these reactors?
Nieto-Perez: The process that creates energy in a traditional nuclear reactor is fission, where a heavy nucleus is hit with a neutron and split into two smaller nuclei, releasing energy. Since the neutron has no electrical charge, it has no problem colliding with a positively charged nucleus, but in fusion, the colliding nuclei contain two positively charged protons that actively repel one another away. To overcome this natural repulsion, the particles must be heated to extremely high temperatures — over a million degrees Celsius. This heating and the problems associated with it are what have kept a commercial fusion reactor elusive for so many years.
Increasing understanding of the physical processes at play in fusion reactors, as well as advancements in technologies like high-temperature superconducting magnets, powerful microwave sources and artificial intelligence, have started addressing these difficulties. Our work seeks to remedy some of the material-based challenges facing fusion reactors by using materials that can withstand much higher temperatures and continuous damage from neutrons and radiation.
Q: How will your research team contribute to the project?
Wang: We will investigate new ways of implementing flowing liquid metals into the construction of fusion devices, while simultaneously developing novel liquid metal mixtures. Currently, most fusion reactors use magnets to confine extremely hot, ionized gas known as plasma. No matter how carefully we construct these magnetic fields surrounding the system, however, we experience some plasma leakage. Modern fusion machines can protect the system by channeling the leaking plasma to a component known as the divertor, but over time, these divertors will erode and break down from the constant impact of plasma and radiation.
Flowing liquid metals offer a promising alternative to the traditional metals currently used in divertor construction, as liquids can more efficiently remove heat and are inherently resistant to radiation damage because their atoms can continuously reorganize to heal defects. Although using liquids as plasma-facing materials requires precise control of their flow, the primary focus of our group’s work will be implementing a capillary porous system into the walls of the reactor — allowing us a great deal of precise control over where the metal travels in the system and how it gets there.
Plasma, an extremely hot ionized gas, can be very damaging to the components powering nuclear reactors. The team's research fires plasma at liquid metal compounds in vacuum chambers to determine the best mixtures to implement into reactor designs. Credit: Caleb Craig/Penn State.
Q: What liquid metal mixtures will you use in your work?
Nieto-Perez: We will begin with liquid lithium because of the key advantages offered by its isotopes — a version of an element that contains a different number of neutrons, which you can think of as a different species of the same animal. When a neutron hits a specific isotope, known as lithium-6, the isotope splits into different chemical fragments, including an element known as tritium that can be used as fuel for fusion. Liquid lithium also has both excellent thermal properties and plasma-confinement capabilities. We plan to explore other novel materials in the future, such as mixtures of metals with high and low atomic numbers like tin-lithium and tin-aluminum alloys.
Q: What institutions will you be collaborating with on this project?
Wang: This FIRE project is led by Princeton Plasma Physics Laboratory and includes members from the University of Illinois Urbana-Champaign, Princeton University, ExoFusion, Oak Ridge National Laboratory, Lawrence Livermore National Laboratory, Massachusetts Institute of Technology, Virginia Commonwealth University and Penn State. Achieving our project goals requires expertise not only in nuclear engineering, but also in materials science, mechanical engineering, electrical engineering, artificial intelligence and machine learning. We welcome interested students to reach out and join this exciting research effort.
The research team consists of (From left to right): Xing Wang, Ama Dahanayake, Chase Hargrove, Calixto Gabriel Alvarado and Martin Nieto-Perez. Credit: Caleb Craig/Penn State.
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