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The US Department of Energy (DoE)’s Oak Ridge National Laboratory (ORNL) has completed successful testing of two 3D printed stainless steel capsules in the High Flux Isotope Reactor (HFIR).
Supported by the DoE’s Office of Nuclear Energy’s Advanced Materials and Manufacturing Technologies program, the project involved fabricating the capsules at ORNL’s Manufacturing Demonstration Facility (MDF) using laser powder bed fusion (LPBF) and 316H stainless steel.
This material is being assessed for its suitability in nuclear environments due to its strength at high temperatures, corrosion and radiation resistance, and compliance with stringent safety standards.
“As we demonstrate the reliability of these printed components, we’re looking at a future where additive manufacturing might become standard practice in producing other critical reactor parts,” said Ryan Dehoff, Director of the MDF at ORNL.
Additive parts tested for durability
Once fabricated, the capsules were assembled and qualified by ORNL’s Irradiation Engineering group. They were then placed inside HFIR, where they underwent a month-long irradiation cycle. After testing, both capsules were retrieved fully intact, demonstrating their structural integrity and performance under extreme conditions.
These experimental capsules are designed to hold sample materials during irradiation, acting as both containment barriers and pressure vessels. HFIR’s intense neutron environment, among the highest in the world, provides researchers with the ability to test materials and fuels under realistic reactor conditions.
Traditionally, irradiation capsules require custom designs and specialized materials, making the development process both time consuming and expensive. ORNL researchers are exploring additive manufacturing as a faster, more cost-effective alternative that also offers greater flexibility in design.
“Additive manufacturing will expand my group’s toolset to develop innovative experiments to support this critical need,” said Richard Howard, a group leader in the Nuclear Energy and Fuel Cycle Division at ORNL.
Earlier this year, ORNL 3D printed and tested a stainless steel rabbit capsule using LPBF, marking the first time AM was applied to this type of nuclear component. After being assembled, sealed, and inserted into HFIR, the capsule withstood nearly a month of irradiation and remained fully intact. A post-irradiation analysis is planned for winter to further evaluate its performance and potential future uses.
Demonstrating enhanced reactor performance using 3D printed parts
Additive manufacturing is changing how the nuclear sector designs, maintains, and supports critical equipment, making the process more adaptable, efficient, and reliable under strict regulatory standards.
Last year, Westinghouse Electric Company used 3D printing to develop a new filtering bottom nozzle aimed at improving fuel assembly performance in Pressurized Water Reactors (PWRs). Integrated into four lead test assemblies at the Joseph M. Farley Nuclear Plant, the design specifically targeted debris fretting, a key contributor to fuel rod leakage.
Having used 3D printing, engineers were able to create more refined geometries that limited the size of debris entering the reactor. During testing, the nozzles demonstrated a 30% increase in resistance to debris, highlighting the potential of AM to enhance reactor component reliability.
Elsewhere, researchers at the Korean Atomic Energy Research Institute successfully used a combination of 3D printing and CNC machining to produce a 30 kg safety valve for use in a nuclear reactor. The valve featured intricate internal cooling channels and met the stringent requirements for ‘Class 1’ nuclear safety classification.
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Featured image shows 3D printed stainless steel capsules. Image via ORNL.
