DOE Approves Xcimer's Athena Preconceptual Design, Backing a 400 MW Laser Fusion Plant Cooled by a Molten-Salt Wall
The Department of Energy accepted Xcimer Energy's preconceptual design and roadmap for Athena, a planned 400 MW laser fusion plant the company aims to operate in the mid-2030s.
Overview
The U.S. Department of Energy has formally approved Xcimer Energy’s preconceptual design and technology development roadmap milestone for Athena, the Denver company’s planned laser fusion power plant, according to World Nuclear News. The acceptance, announced June 10, 2026, covers both the plant design and the roadmap to build it, and positions Xcimer among the front runners to commercialise fusion energy, the outlet reported.
Xcimer expects to be operating Athena as a 400-MW fusion power plant in the mid-2030s at a site to be determined, the American Nuclear Society reported.
What We Know
The approval rests on a 724-page submission that provided DOE reviewers with a detailed assessment of plant performance targets, economics, system-level engineering requirements, safety and environmental analyses, and technology development pathways, according to World Nuclear News. POWER Magazine described Athena as the reference architecture for the Denver-headquartered company’s plant, designed for continuous operation with a chamber requiring no first-wall replacement.
Athena would be designed for continuous grid-scale electricity generation, integrating the laser platform with target delivery, a fusion chamber, tritium breeding, and power generation systems at an industrial scale, the American Nuclear Society reported.
The design centers on a liquid-wall chamber intended to solve a durability problem that has dogged other fusion concepts. “One reason other fusion chamber designs face a durability problem is that they put solid material where the fusion neutrons go. We don’t. The molten salt curtain absorbs and moderates the flux, breeds fuel, and carries the heat - and it flows, so it renews itself continuously,” Susana Reyes, vice president for chamber and plant design, said in the World Nuclear News report. “A commercially attractive power plant looks very different from a scientific breakthrough facility. We are designing Athena to run continuously at a repetition rate of up to 1 Hz, and the use of a liquid wall chamber maximises availability by protecting the solid structures from the fusion reaction emissions over the entire plant lifetime,” she added.
The milestone follows the recent launch of Xcimer’s prototype laser system, code-named Phoenix, which the company calls the largest privately owned laser system in the world, according to World Nuclear News. Phoenix uses a krypton fluoride excimer laser using Stimulated Brillouin Scattering to compress a microsecond-long pulse, the outlet reported, and is housed in a 74,000-square-foot Denver laser facility, per POWER Magazine. The light source for Phoenix operates at pulse energies over 1 kJ, and the SBS gas optic at the core of Phoenix is 38 meters long, the American Nuclear Society reported.
Athena is being developed with support from the DOE’s Milestone-Based Fusion Development Program, and the acceptance follows Xcimer’s completion of earlier program milestones over the first 18-month budget period, the American Nuclear Society reported. Xcimer was one of eight companies selected by the DOE in June 2023 to share USD46 million under that program, with Xcimer awarded USD9 million, according to World Nuclear News.
Before the full plant, Xcimer plans an intermediate demonstration. Vulcan, planned for the early 2030s, is an engineering breakeven demonstration that will combine 40 Argos laser modules to produce 4 megajoules of laser light to demonstrate net energy gain from laser fusion, the American Nuclear Society reported.
Xcimer chief executive, chief science officer and co-founder Conner Galloway framed the approval as a shift from physics to engineering. “The question facing laser fusion is no longer whether the physics works. The question is how fast we can industrialise it. DOE’s acceptance of Athena reflects both the strength of our technical approach and our ability to execute against an ambitious commercialisation roadmap,” he said in the World Nuclear News report.
What We Don’t Know
A preconceptual design and roadmap acceptance is an early-stage milestone, not a regulatory license or a guarantee of performance. The site for Athena has not been determined, the American Nuclear Society reported, and neither the company nor the DOE has disclosed a construction timeline or total project cost beyond the mid-2030s operating target. Xcimer must still demonstrate net energy gain at Vulcan before Athena’s economics can be validated at scale.
Analysis
Xcimer pursues inertial confinement fusion, the same broad approach the National Ignition Facility used to achieve scientific energy gain. The company competes with other inertial-confinement ventures, including Inertia Enterprises, which the Machine Herald previously reported had licensed roughly 200 patents from Lawrence Livermore National Laboratory to commercialize NIF science. Xcimer’s differentiator is its laser architecture and the molten-salt liquid-wall chamber, which the design treats as a way to renew the chamber wall continuously rather than replace solid first-wall material exposed to neutron flux. Whether that translates into a buildable, financeable 400 MW plant in the next decade remains the open question the DOE milestone does not resolve.