U.S. Lays Foundation for Fusion Energy Future with Liquid Metals Strategy

A national research program strategy focusing on the use of liquid metals in fusion systems was discussed on January 22 at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL). This inaugural meeting addressed liquid metal infrastructure needs and identified technology and science gaps, as outlined in the DOE's Fusion Science and Technology Roadmap from October 2025.

Research indicates that liquid metals could protect components exposed to plasma heat and enhance fusion system performance. PPPL, known for its expertise in liquid metals, hosted the meeting, which saw over 75 attendees both in person and online. Participants included researchers from U.S. national laboratories, universities, DOE personnel, and private sector fusion leaders.

Jean Paul Allain, FES Associate Director, stated that the Roadmap identified liquid metals as a potentially transformative technology for achieving fusion power, and participant insights would inform the development of a U.S. liquid metal program.

The DOE's goal is to support a competitive U.S. fusion power industry and demonstrate fusion power plants, which could provide a stable and diversified energy source, ensuring U.S. energy independence. Refining the use of liquid metals in tokamaks, which confine plasma using magnetic fields to release energy, is a key aspect of fusion research.

Heather Jackson, Division Director for Fusion Enabling Science and Partnerships at FES, emphasized the program's aim to develop not only the first fusion power plant but also an economically competitive industry.

Josh King, a program manager at the DOE's FES, thanked private sector companies for their contributions, noting that their input helps understand research needs and optimize investment impact.

PPPL's Pivotal Role in Liquid Metals Research

PPPL plays a significant role in liquid metals research for fusion applications, particularly with liquid lithium, collaborating with global public and private partners. PPPL also leads a national Fusion Innovation Research Engine collaborative focused on advancing liquid metal technology and science. The National Spherical Torus Experiment-Upgrade, PPPL's primary fusion experiment, is intended to serve as a test bed for liquid metal components.

Rajesh Maingi, head of tokamak experimental science at PPPL, highlighted the infrastructure required to transition liquid lithium technology from laboratory to power grid. This includes additional test facilities for validating liquid metal behavior in strong magnetic fields and under plasma bombardment, reliable methods for extracting and purifying tritium from flowing lithium, and a domestic supply chain for specialized materials. PPPL's decades of research position it to build this foundation.

Advancing Research: Key PPPL Projects

Current PPPL Liquid Metals Projects

• Lithium Tokamak Experiment-𝛽: A small tokamak that has provided insights into the effects of liquid metal coatings, with walls almost entirely coated in liquid lithium.
• Lithium Vapor Divertor Development: Aims to reduce high plasma heat flux that could melt solid walls in fusion systems. Experiments measure how lithium vapor generation changes with surface temperature and impurities.
• Lithium EXposure and Interaction (LEXI) Experiment: Investigates interactions between liquid lithium and container metals and porous structures. This facility maintains over 100 grams of liquid lithium above 300 degrees Celsius for extended periods, allowing observation of material changes.
• Theoretical Work: Focuses on liquid metal blankets for heat capture, plasma-wall interactions, and liquid metal flows in magnetic fields.

Recently Initiated Projects

• Liquid Lithium Magnetic Centrifuge: Designed to study the separation of protium and deuterium from liquid lithium, critical for future fusion system design.
• Liquid Metal Ultrasonic Diagnostic Development: A new system for measuring liquid metal flow speed without cameras, initially tested with Galinstan (a lithium surrogate) before adapting for liquid lithium.
• Lithium Experimental Application Program (LEAP): The first in a series of platforms to study liquid metal behavior under conditions replicating future fusion systems. It will handle significantly more lithium than previously licensed, enabling comprehensive testing of liquid metal plasma-facing components.