Oak Ridge National Laboratory’s Manufacturing Demonstration Facility (MDF), in collaboration with reactor developer Kairos Power and Barnard Construction, has developed and deployed large-format 3D printed polymer composite molds to cast high-precision concrete structures at the Hermes Low-Power Demonstration Reactor. The forms, fabricated using carbon-fiber-reinforced ABS, are being used at Kairos Power’s Oak Ridge campus in Tennessee. Each section measures approximately 10 by 10 feet and is stacked three units high to form a column.
The printed molds were used in the Janus shielding demonstration and serve as a precursor to the formwork that will be implemented in the Hermes bioshield system. A portion of one column form was displayed at the East Tennessee Economic Council’s Nuclear Opportunities Workshop, held July 22–23 at the Knoxville Convention Center. The composite molds enable cast-in-place fabrication of complex concrete components in significantly less time than conventional steel or wood formwork.
“We’re showing that the future of nuclear construction doesn’t have to look like the past,” said Ryan Dehoff, director of the MDF. “We’re combining national lab capabilities with MDF’s legacy of taking big, ambitious swings — moonshots that turn bold ideas into practical solutions — to accelerate new commercial nuclear energy.”
MDF has previously led additive manufacturing initiatives across sectors, including the development of 3D printed cars and houses and real-time part qualification tools. The current work applies these principles to nuclear infrastructure. Kairos Power’s reactor development model emphasizes rapid learning cycles and early-stage validation. Edward Blandford, co-founder and CTO of Kairos Power, said the collaboration began following advice from a commercial partner: “It’s not often we get advice from industry to call the national lab because they move quickly.”
Blandford explained that the use of prototype molds allowed the team to refine techniques and reduce risk. “This project fits squarely into our iterative development approach,” he said. “By building and testing the molds for the columns first, we’re able to refine our methods, engage early with regulators, and reduce risk before we scale up the construction method for Hermes and future plants.”
The Janus columns demonstrate an element of the Hermes bioshield, a thick concrete barrier designed to absorb radiation during reactor operation. According to Ahmed (Arabi) Hassen, composites innovation group leader at ORNL, the molds had to meet both geometric tolerances and structural requirements to contain the hydrostatic pressure of poured concrete. The printing process was optimized to ensure mechanical resilience and dimensional stability under stress.
Barnard Construction worked directly with MDF and Kairos Power to implement and adapt the molds in the field, providing real-time feedback and integrating design changes to improve constructability. Industry partners Airtech, TruDesign, Additive Engineering Solutions, and Haddy supported mold fabrication and logistics, forming a new supply chain model for nuclear construction through additive manufacturing.
The project is part of the SM2ART Moonshot Project, a multi-year initiative led by MDF and the University of Maine and funded by the Department of Energy’s Advanced Materials and Manufacturing Technologies Office. The program focuses on modernizing energy infrastructure through large-scale additive manufacturing, bio-based composite materials, and integrated digital platforms. ORNL contributes expertise in materials science, supercomputing, and artificial intelligence, while the University of Maine supports structural system development and digital manufacturing.
Over the next 18 months, the program will expand to full-scale production of formwork for additional elements of the Hermes reactor, including radiation shielding and building enclosures. The team plans to integrate digital twins and data-driven quality assurance while transitioning to printable biocomposite feedstocks derived from timber residuals. The material strategy targets a 75% reduction in cost using domestically sourced forest byproducts.
Hermes is the first advanced reactor to receive a construction permit from the U.S. Nuclear Regulatory Commission. Located within the Knoxville–Oak Ridge region, the country’s most concentrated nuclear technology corridor, the reactor represents a case study in applying advanced manufacturing to fission infrastructure.
“This project shows that we can break through old methods with new technologies that lower barriers, reduce risk, and accelerate construction timelines,” said Hassen. “We’re taking the best of additive manufacturing — modularity, flexibility, rapid iteration — and applying it to nuclear energy.”
UT-Battelle manages Oak Ridge National Laboratory for the Department of Energy’s Office of Science, which is the largest supporter of basic research in the physical sciences in the United States.
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Featured photo shows looking down on the Janus gate from above, the 3D printed form is visible next to the concrete pillars arranged in a radiation symbol. Photo via Kairos Power.
