U.S. Marathon Fusion Demonstrates Hydrogen and Lithium Isotope Enrichment Technology

U.S.-based Marathon Fusion announced on August 27 that it has successfully demonstrated hydrogen and lithium isotope enrichment technology using its proprietary plasma centrifuge. The company stated that this advancement addresses the fuel cycle needs of fusion energy and related isotope supply requirements.

In the deuterium-tritium fusion pathway, hydrogen isotope processing is critical to the continuous operation of fusion devices, while lithium isotope enrichment is closely tied to tritium production. The U.S. Department of Energy (DOE) released its "Fusion Science and Technology Roadmap" in June of this year, which identifies tritium processing as one of the core challenges, noting that related progress plays an important role in achieving sustained deuterium-tritium fusion operation and validating the feasibility of fusion as a large-scale energy form.

Marathon Fusion stated that its plasma centrifuge is designed to enable a differential pumping process, which has the potential to reduce tritium throughput and the scale of associated tritium processing systems. The company reported that initial separation results have reached levels that could significantly reduce tritium flow in the fusion fuel cycle. The technology was developed with funding from the U.S. Department of Energy Advanced Research Projects Agency–Energy (ARPA-E) through the VISION OPEN program, and Marathon Fusion is one of three private fusion companies supported under this program.

Dennis Whyte, Professor of Nuclear Science and Engineering at the Massachusetts Institute of Technology (MIT), stated that Marathon Fusion's achievements in isotope separation are significant for the fusion industry. In his view, if the technology can achieve selective tritium pumping, it could reduce the required tritium inventory while improving fusion power plant performance; the same technical approach could also be applied to improve lithium isotope separation, which is considered a key step in enhancing tritium production efficiency at fusion power plants.

Lithium isotope supply is also regarded as a critical issue in the fusion supply chain. The Special Competitive Studies Project (SCSP), founded by former Google CEO Eric Schmidt, previously released a report stating that lithium enrichment is one of the higher-risk gaps in the fusion supply chain, noting that the United States currently lacks domestic commercial supply.

Per F. Peterson, Distinguished Professor of Nuclear Engineering at the University of California, Berkeley (UC Berkeley) and advisor to Marathon Fusion, stated that FLiBe, composed of lithium fluoride and beryllium fluoride, offers attractive properties as a coolant for nuclear energy systems due to its high volumetric heat capacity and strong neutron moderation capability. He noted that the lithium in FLiBe requires isotopic enrichment: fusion reactions require enriched lithium-6, while fission systems require enriched lithium-7. Current global annual production of enriched lithium is less than one ton, with limited process supply, and future terawatt-scale deployment would require large-scale clean lithium enrichment technology to support it.

Marathon Fusion stated that the experimental results closely match computational models, validating its underlying theory and providing predictive modeling basis for subsequent system design. With the enrichment technology validated, the company plans to build its first commercial pilot facility to produce isotopes capable of supporting gigawatt-scale fusion device deployment.

Charles Swanson, Vice President of Fusion Systems at Thea Energy, stated that isotope separation is a critical step in the fusion fuel cycle, and Marathon Fusion's experimental results demonstrate a technical pathway that could make related systems smaller and more practical.

Marathon Fusion is primarily engaged in isotope production, with business directions including supplying radioisotopes for the radiopharmaceutical industry and developing isotope technologies for fusion energy. The company has received support from ARPA-E, the Breakthrough Energy Fellows program, the 1517 Fund, and Übermorgen Ventures, among others.