With AMA: Energy 2026 just around the corner, 3D Printing Industry is taking a closer look at the role of additive manufacturing in the energy sector.
Nuclear construction is slow, expensive, and resistant to change, a combination that has constrained the industry for decades. US largest multi program science and technology laboratory Oak Ridge National Laboratory is working to change one part of that equation, applying large-format additive manufacturing to the fabrication of structural reactor components in a way that cuts construction timelines from months to weeks while opening up geometries that conventional formwork cannot produce.
The work is led by Ahmed Arabi Hassan, group leader for the composite innovation group at ORNL’s Manufacturing Demonstration Facility. With the first molten salt reactor in the United States now underway on the historic K-25 site in Oak Ridge, the project has moved from demonstration to live deployment.
The Lab and the Scale-Up Problem
The ORNL is the largest national laboratory under the Department of Energy’s Office of Science, with a $2.6 billion budget and over 7,000 employees. Its history includes developing the world’s first continuously operated nuclear reactor, and today its capabilities range from two of the world’s most intense neutron sources to the 110,000‑square‑foot Manufacturing Demonstration Facility, where Hassan’s group integrates additive manufacturing, conventional composites, machining, and powder‑bed systems.
In an interview with Ryan Dehoff, Director of the MDF, the lab’s entry into nuclear additive manufacturing was described as a rapid evolution. “About six years ago, we started really getting interest from the nuclear folks on using that technology and moving quickly, trying things out, prototyping, moving to production,” he said. “It’s a pretty rapid evolution of technology, insertion, and maturation.”
All ORNL capabilities function as user facilities, accessible to industry, universities, and other national laboratories through collaborative agreements. “This structure targets the advanced manufacturing “valley of death,” the mid-scale-up stage where private investment is scarce and promising technologies often stall,” explained Hassan.
A key challenge underlying all of it, Dehoff noted, is that the industry has historically approached AM with the wrong starting point. “We took the chemistry and then just put it into 3D printers and thought everything was going to be great,” he said. “But we don’t have those same processing steps, and so we get variations in the material.” Legacy alloys optimized for casting or forging behave differently under AM conditions, and ORNL’s materials research, focused heavily on 316H stainless steel and nickel alloys, is working to close that gap by designing materials specifically for additive processes rather than adapting them from conventional ones.
Central to the group’s approach is convergence manufacturing: combining AM, subtractive, and forming processes into a unified production workflow, connected by a continuous digital thread of sensing, simulation, and data-driven optimization. This integration enables functional complexity and dimensional performance beyond the reach of any single process.
The group’s scale-up experience illustrates the value of this model. Early large-format printing trials suffered significant warping from thermal expansion. Incorporating discontinuous carbon fiber into the thermoplastic matrix stabilized the composite, increasing throughput from 40 to 100 pounds per hour.
Printing the Infrastructure for Kairos Power’s Molten Salt Reactor
Kairos Power is building the Hermes test reactor on the historic K-25 site in Oak Ridge, the first molten salt reactor of its kind in the United States. The project involves complex structural elements, including four 40-foot tall strong backs that support the reactor vessel and act as holders for cast-in-place concrete. Their stair-step geometry, required for precise brick alignment, made conventional steel or wooden formwork expensive, slow, and difficult to modify.
To address this, ORNL designed modular, 3D printed formwork using carbon fiber-reinforced ABS, producing stackable six-foot sections. Modularity allowed for both design flexibility and logistics efficiency: if a section failed or required revision, only that module needed replacement. Finite element analysis guided wall thickness and internal truss geometry, ensuring the printed forms could withstand the hydrostatic pressure of 18 feet of concrete during pouring.
“From CAD files to first concrete pour in fourteen days, within ±4 millimeters. The forms were reused across multiple pours, so the cost and time benefits compounded with every use. That’s the efficiency case for additive manufacturing in nuclear construction,” said Hassan.
Building on this success, Kairos Power and ORNL extended the approach to radiation shielding for the reactor. Traditional shielding relies on straight brick-cast panels joined with labor-intensive grouting, limiting geometric possibilities. The team is printing 27-foot-tall polymer inserts for sinusoidal, interlocking precast concrete panels that create a tortuous path for radiation, reducing leakage and eliminating grouting.
Hassan stressed that each phase of construction relies on a tightly integrated data stack: material characterization, in-line IR and sensor monitoring during printing, post-print 3D scanning, and structural performance testing. These datasets feed AI and machine learning systems to optimize design geometry and process parameters.
“The goal is not merely to build one reactor faster, but to transform large-format nuclear construction from a one-off engineering effort into a repeatable, data-driven workflow, establishing additive manufacturing as a standard tool for the industry,” Hassan emphasized.
A Broader Push to Rebuild Nuclear With Additive Manufacturing
The Kairos Power collaboration is part of a broader, years-long effort to modernize the U.S. nuclear industry. Most domestic nuclear power today comes from reactors built between 1967 and 1990. Decommissioning is now outpacing new construction, and the number of operational reactors has declined from a peak of 112 in 1990 to 92 in 2022, with only three large reactors coming online in the past 28 years. In response, the Department of Energy is targeting three new test reactors by the end of 2026 and its first operational microreactor in 2028, timelines that conventional construction methods have historically struggled to meet. Additive manufacturing is emerging as a critical enabler of this accelerated schedule.
ORNL has been laying the groundwork for this transformation. In 2021, four 3D printed fuel assembly brackets, developed in partnership with the Tennessee Valley Authority (TVA) and Framatome, were installed at TVA’s Browns Ferry Nuclear Plant in Alabama, reportedly marking the first 3D printed safety-related components ever placed in an operational reactor.
More recently, ORNL pushed that boundary further by testing 3D printed rabbit capsules inside a nuclear reactor for the first time. These small stainless steel components, printed using laser powder bed fusion, house experimental materials during irradiation and must contain fission gases produced during nuclear reactions.
They were placed into ORNL’s High Flux Isotope Reactor for nearly a month and successfully withstood the high neutron flux environment. What made the result particularly significant was the geometry: Dehoff explained that a known failure mode is the capsule wall buckling under pressure and getting stuck in the reactor, so ORNL engineered shapes that fail in controlled, predictable ways to prevent that outcome. Those geometries, he noted, “cannot be produced using any other manufacturing method.”
The Kairos Power project represents the next step in this progression, extending additive manufacturing from individual reactor components into the larger structural and operational infrastructure that surrounds them, demonstrating how the technology can accelerate not just parts production but entire nuclear construction workflows.
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