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Nuclear energy is making a comeback in the United States. Ryan Dehoff, director of ORNL’s Manufacturing Demonstration Facility (MDF), believes 3D printing will play a vital role in this revival.
Currently, almost all U.S. nuclear power is generated by reactors built between 1967 and 1990. Meanwhile, decommissioning is outpacing construction. The number of operational reactors peaked at 112 in 1990, but had fallen to 92 by 2022, with just three large reactors coming online in the last 28 years.
However, energy demand is surging as artificial intelligence (AI) drives the construction of power-hungry data centers. The U.S. plans to meet this need with a nuclear-driven solution. The Department of Energy (DOE) is working to build three new test reactors by the end of 2026 and launch its first operational microreactor in 2028 as part of its mission to expand America’s atomic output.
Oak Ridge National Laboratory (ORNL), one of the DOE’s primary national energy labs, is leading research that is shaping the future of American nuclear development. Founded as part of the Manhattan Project, the lab sees additive manufacturing as central to these efforts.
During a recent conversation with 3D Printing Industry, Dehoff discussed the organization’s efforts to enhance in-situ inspection, overcome certification challenges, and accelerate nuclear energy supply chains.
In addition to heading MDF operations, the 16-year ORNL veteran is the Technical Area Lead for Advanced Manufacturing at the lab for DOE’s Office of Nuclear Energy AMMT Program. In addition to ORNL, the AMMT Program includes efforts at Argonne, Los Alamos, Idaho, and Pacific Northwest national laboratories.
Dehoff explained ORNL’s two-pronged approach, which combines in-reactor testing with the lab’s AI-powered Peregrine software. Dehoff’s team aims to provide machine manufacturers and regulators with the data needed to certify 3D printed metals for critical nuclear systems.
ORNL leverages laser powder bed fusion (LPBF) for small, intricate test capsules; wire-arc deposition for large nuclear valves and pumps; powder-metallurgy HIP for multi-ton impellers; and large-format polymer extrusion for construction. Together, these projects drive a broad push to cut costs, shorten timelines, and enable complex geometries.
ORNL’s Advanced Manufacturing Push
Dehoff joined ORNL as a materials scientist in 2009 and has led the MDF since 2022. “I’m a metallurgist by training, and I’ve spent pretty much my entire career related to advanced manufacturing technologies,” he said.
Established in 2012, the MDF is funded by the DOE Office of Energy Efficiency and Renewable Energy’s Advanced Materials & Manufacturing Technologies Office. Located at ORNL’s Knoxville, Tennessee, campus, MDF is leading innovation in additive manufacturing, composites, novel alloys, ceramics, machining and machine tools, convergent manufacturing, robotics, automation and controls, smart manufacturing, and powder metallurgy – hot isostatic pressing (PM-HIP).
For 3D printing, the MDF collaborates with equipment suppliers, materials providers, and other industrial partners to tackle manufacturing certification challenges and advance the technology into mainstream nuclear production.
“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,” Dehoff explained. “It’s a pretty rapid evolution of technology, insertion, and maturation.”
ORNL’s MDF houses a slew of AM technologies, including metal LPBF, electron beam additive manufacturing, and polymer extrusion. The AMMT leverages these technologies to support DOE’s efforts to advance nuclear energy science and technology to meet the nation’s energy and economic needs.
The program primarily focuses on metal powder bed fusion and uses MDF’s LPBF systems to explore materials such as 316H, a high-carbon variant of 316 stainless steel. The program tests performance on Renishaw, Concept Laser, and EOS 3D printers. According to Dehoff, AMMT is running a “round robin” study with other national labs to compare how identical machines perform in different locations.
3D printing nuclear hardware
Dehoff’s team is working to understand how to ensure that the materials produced with 3D printing are “fit for service and will withstand the conditions that are required for nuclear environments.” He described ORNL’s approach as “graded,” starting with components that have lower safety consequences and gradually moving to more demanding applications.
ORNL has already produced 3D printed parts for operational nuclear reactors. The first, Dehoff noted, was a set of fuel assembly brackets installed in the TVA Browns Ferry reactor. Developed with the DOE and French nuclear reactor company Framatome, the brackets were successfully installed in 2021 and are scheduled to remain in operation until 2027.
The team used a digital qualification approach that combines 3D printer sensor data with advanced modeling to predict how the components would perform under extreme nuclear conditions. “That understanding gave us confidence that the parts would survive inside the reactor,” Dehoff said. Once removed, the brackets will undergo Post Irradiation Examination (PIE) to assess how atomic environments affect 3D printed materials compared with conventionally manufactured parts.
More recently, ORNL conducted the first test of 3D printed rabbit capsules inside a nuclear reactor. Rabbit capsules are small metal components that house materials for irradiation experiments and contain fission gases that are produced during nuclear reactions. They are used in fuels and materials research to house experiments undergoing irradiation.
ORNL 3D printed the stainless steel capsules using LPBF technology. They were then loaded with the experimental material and sealed before being placed into the High Flux Isotope Reactor, a DOE Office of Science user facility at ORNL, for nearly a month. During exposure, the rabbit capsules successfully withstood the reactor’s demanding high neutron flux environment.
Dehoff explained, “One failure mechanism of those capsules is that, as you start to pressurize them, the wall can buckle and expand, potentially getting the capsule stuck in the reactor.” Using 3D printing, ORNL engineers designed unique geometries that fail in controllable ways to prevent such problems.
These shapes also unlock performance and cost efficiencies. While Dehoff could not reveal the exact nature of the designs, he noted that they cannot be produced using any other manufacturing method.
Additive manufacturing also offers value for large-scale metal parts. Away from LPBF, ORNL is working with directed energy deposition (DED) and wire arc additive manufacturing (WAAM) systems developed by Cleveland-based Lincoln Electric, with whom ORNL shares an “excellent relationship.”
Dehoff highlighted PM-HIP as another technology ORNL is pursuing. The process applies high temperature and pressure to a sealed metal canister of powder, consolidating it into fully dense, solid components. According to Dehoff, a key challenge is ensuring the canister is fabricated perfectly to prevent deformation in the final part.
“A lot of people are trying to use predictive models to predict that distortion change,” Dehoff explained. “That’s pretty hard to do, and it limits some of the economics of using PM-HIP as a process.”
ORNL used additive manufacturing to produce a canister for a six-foot impeller. The canister was filled with powder, welded shut, and processed through the HIP cycle. The result? A “really large impeller,” where 3D printing has “driven down the cost of the R&D to get the final geometry.”
Can additive manufacturing be used to produce 3D printed nuclear reactor cores? This is a question ORNL sought to answer back in 2020 with DOE’s Transformational Challenge Reactor (TCR) Demonstration Program.
At the time, the lab announced plans to build an additively manufactured microreactor, targeting operation by 2023. To meet this aggressive timeline, it leveraged metal 3D printing, advanced materials, and integrated sensors and controls to enhance optimization and lower costs. Since the 2020 announcement, however, updates on the TCR have been scarce.
When asked about the project, Dehoff explained that ORNL researchers had designed and built a mock-up of the reactor core but could not secure the fuel required for testing. The program was later absorbed into the AMMT initiative, shifting its focus toward helping the nuclear industry de-risk additive manufacturing materials and processes.
Targeting high-volume 3D printing
ORNL’s research components are produced in low volumes. However, Dehoff noted that nuclear technology company Westinghouse is using 3D printing to scale production of nuclear reactor components.
For example, the Pittsburgh-based firm has used metal additive manufacturing to produce over 1,000 fuel flow plates for its VVER-440 nuclear reactor. The company says these are the first safety-related 3D printed components to enter serial production.
Westinghouse has also developed “first-of-its-kind” filtering bottom nozzles to improve debris capture and extend the fuel endurance of nuclear reactors. Engineers installed four lead test assemblies with the 3D printed nozzles at Alabama Power’s Joseph M. Farley Nuclear Plant, operated by Southern Nuclear.
Additive manufacturing increased design flexibility, allowing engineers to reduce the size of debris that could enter the reactor. In testing, the components showed a 30% increase in resistance to debris.
Dehoff called Westinghouse’s work a “fantastic precedent for, potentially, what’s to come.” He noted that the company has seen “some tremendous benefits” when scaling additive manufacturing to higher volumes. “In the future, I think we’ll see a lot more companies doing that with a lot more benefit,” he added.
Designing Materials for Additive Manufacturing
During our conversation, Dehoff emphasized that one of the key opportunities in nuclear additive manufacturing lies in designing materials specifically for 3D printing. Inside a nuclear reactor is “one of the most aggressive environments on the planet,” he explained. “To get materials to operate in there is always a challenge.”
According to Dehoff, many in the 3D printing industry initially leveraged materials used in legacy manufacturing when exploring nuclear applications. However, these alloys have been optimized for a specific legacy manufacturing technology. “We took the chemistry and then just put it into 3D printers and thought everything was going to be great,” Dehoff said. “But we don’t have those same processing steps, and so we get variations in the material.”
By contrast, materials optimized for additive manufacturing have the potential to achieve superior performance. While nuclear research in this space remains limited, proprietary 3D printing materials have achieved impressive performance in other demanding verticals.
In aerospace, for example, high-temperature aluminum alloys designed for 3D printing have shown performance gains. Dehoff argued that applying similar concepts to nuclear manufacturing could unlock higher-performing materials, but additional research is still required.
ORNL’s nuclear material research focuses heavily on 316H stainless steel. Its performance is well-documented in conventional processes like melting, alloying, and casting. However, in additive manufacturing, the material develops unique microstructural behaviors that do not appear in traditional processing.
In contrast, 316L, commonly used in metal additive manufacturing, forms a predictable, uniform chevron-like grain structure regardless of process parameters. 316H, meanwhile, develops grains that align in specific directions, a behavior that remains poorly understood.
This directional alignment, or anisotropy, can create challenges because engineers generally prefer materials with consistent microstructural properties in all directions. Dehoff’s team is investigating why 316H behaves this way and how to process it to produce reliable, high-strength components.
ORNL research also explores nickel alloys such as 625, which “may play an important role in the next generation of nuclear reactors.” It also considers various other refractory materials, indicating a broad range of materials under consideration for nuclear additive manufacturing.
Building a digital thread with AI software
Another major focus of ORNL’s additive manufacturing research is data collection and traceability. Dehoff pointed to Peregrine, Oak Ridge’s proprietary AI-powered software tool. It leverages a camera and an AI algorithm to track each layer during the LPBF 3D printing process.
The tool detects flaws such as uneven powder distribution, overheating, spatter, distortion, and porosity. Once an error is detected, the software immediately alerts the operator, allowing them to make adjustments and prevent problems in the final part. It can then create a three-dimensional, color-coded reconstruction of each build to help visualize where errors have occurred.
Additionally, Peregrine collects machine data, such as oxygen sensors and temperature sensors, which is combined with post-inspection and modeling data in a comprehensive framework.
“Essentially, we’re building a digital thread of every single component that we manufacture,” Dehoff explained. ORNL is also leveraging model predictions, non-destructive evaluation (NDE) data, and X-ray computed tomography.
“Every time I build a part, I have this tremendous amount of data associated with it,” added Dehoff. “I can, in theory, use the data from the print, combined with the models that are predicting performance, to help accelerate the qualification of that material.
ORNL integrates all this information into its data tool, enabling engineers to trace the full lifecycle of each 3D printed part. The tool tracks everything, from the powder source and the technician who handled it to calibration records, heat treatments, and test sample extraction. Engineers can then feed this data into machine learning models to directly link manufacturing conditions to material performance.
Beyond traceability, ORNL is developing predictive capabilities designed to enhance quality assurance in nuclear components. By combining in-situ imaging with X-ray computed tomography, the team can identify potential defects before they become critical, reducing the need for extensive inspection of 3D printed parts.
According to Dehoff, ORNL’s digital thread could also allow engineers to simulate how a given component will perform 30 years in the future. “We’re pretty far along that pipeline of showcasing how you would do that,” he added.
3D printing and the future of nuclear energy
Dehoff is confident that ORNL’s 3D printing research will play a key role in the future of nuclear energy in the U.S.
As energy demand rises, so does the need to scale infrastructure and build new nuclear power facilities. Dehoff believes advances in large-scale polymer 3D printing could help address construction challenges while keeping costs low.
He highlighted a recent collaboration between ORNL, Kairos Power, and Barnard Construction that used 3D printed polymer molds to cast concrete reactor structures. Traditional concrete molds, whether wood or metal, have significant drawbacks. Wooden forms feature long build times and often present quality issues, while metal forms are costly and complex to fabricate.
By contrast, 3D printing offers a path to high-dimensional accuracy at a fraction of the time and cost. Early results from the project suggest that this approach could dramatically shorten reactor construction timelines and support modular construction techniques.
Additive manufacturing is also showing promise in nuclear fusion, an experimental process that combines two atomic nuclei to release vast amounts of energy. In fusion, hydrogen isotopes are heated to extreme temperatures, creating plasma, a superheated state of matter in which electrons are stripped from atoms.
Because this process exposes materials to intense heat and radiation, fusion components must withstand extraordinary thermal and mechanical stress. Although still experimental, additive manufacturing offers the potential to produce complex, high-performance parts that can meet these extreme demands.
Dehoff pointed to ongoing ORNL research involving tungsten wire and plasma deposition to repair the inner surfaces of a tokamak reactor, which uses magnetic fields to heat plasma and initiate nuclear fusion. These experiments focus on plasma-facing refractory metals, which are difficult to process using conventional methods.
He also sees a clear connection between the growth of energy-hungry data centers and a rising demand for nuclear power. As AI and large-scale computing expand, the need for reliable, high-capacity energy sources will accelerate. For instance, McKinsey & Company estimates that global demand for data centre capacity could grow by nineteen to twenty percent annually through 2030, reaching up to 219 gigawatts by 2030.
Dehoff believes investments from data-driven industries will serve as a catalyst, pushing the nuclear sector to expand capacity and deploy reactors more quickly. He argued that soaring data center demand could provide the nuclear industry with the momentum it has long needed to fuel domestic growth.
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Featured image shows from left, ORNL’s Robert Wagner, Ahmed Arabi Hassen and Ryan Dehoff visited the Hermes site to see the concrete poured into the forms. Credit: ORNL, U.S. Dept. of Energy.
