Engineers at the Princeton Plasma Physics Laboratory (PPPL) in the U.S. are preparing for the assembly of the fusion research device National Spherical Torus Experiment-Upgrade (NSTX-U) expected to begin operations in 2026.
To ensure precise alignment of components, they have created over 50 3D printed prototypes. Central to the NSTX-U is a magnet bundle that combines a 19 ft. toroidal field (TF) magnet with an ohmic heating (OH) coil.
Designed to carry up to 4 million amps, the TF magnet will connect to 12 external coils that stabilize the plasma during experiments. Wrapped around it, the OH coil will generate a 4-kilovolt electric field to induce current and heat the plasma to temperatures required for fusion.
The project’s goal is to evaluate whether these smaller, spherical tokamaks can provide a practical and cost-effective solution for future fusion pilot plants.
“The use of 3D-printed prototypes has been instrumental toward reducing risk and accelerating the schedule,” Dave Micheletti, the NSTX-U Project Director and Deputy Associate Laboratory Director For Engineering. “It allows us to positively confirm that components will fit together and eliminates the risk of rework once final assembly starts. It’s saving both time and money.”
Fine-tuning assembly with 3D prints
To reduce assembly risks, engineers have used 3D printed models. These include a detailed, red plastic replica of the magnet bundle’s top section, measuring 40 inches tall and 2 ft. wide, with plans for additional large models for the lower sections.
“If it were a Hollywood set and you painted the TF-OH 3D print a different color, it would look just like the machine,” said Tom Jernigan, Senior Project Manager on the NSTX-U project. “It’s the best money we ever spent.”
According to the team, 3D printing has also been instrumental in verifying the placement of 36 cooling water lines extending from the top of the magnet bundle, which are crucial for managing the heat of plasma experiments.
Other prototypes, including copper electrical bus bars and various support structures, have allowed the team to make precise adjustments before manufacturing begins. Actual fabrication of the copper bus bars has already started, using an OMAX water jet machine in PPPL’s workshop.
Preparations also involve fitting 2,000 protective plasma-facing tiles in the vacuum vessel’s upper half, with plans to complete the lower half soon. Each tile must be positioned within tolerances of just a few thousandths of an inch to endure the demanding conditions of plasma testing.
Meanwhile, Spanish machinery manufacturing company Elytt Energy technicians have built the four quadrants of the TF magnet and are currently compacting them together with metal straps to ensure even pressure on insulation layers.
They will next wrap the quadrants in fiberglass and inject hot resin through vacuum pressure impregnation (VPI) to create a single, solid magnet. Once the TF magnet is complete, the OH coil will be wound around it and undergo the same process.
The final magnet bundle is expected to be completed by fall 2025. It will then be shipped to PPPL for installation in the NSTX-U’s vacuum vessel. These thorough preparations are designed to eliminate setbacks and confirm the system’s readiness, bringing researchers closer to evaluating whether spherical tokamak designs can support the future of fusion energy.
Improved reactor safety with 3D printed components
Across the broader nuclear sector, additive manufacturing is similarly being harnessed to strengthen reactor components and enable safer, more efficient operations
Last year, Westinghouse Electric Company developed unique filtering bottom nozzles to boost debris capture and improve fuel endurance in Pressurized Water Reactor (PWR) fuel assemblies.
Four test assemblies with these nozzles were delivered to Southern Nuclear’s Joseph M. Farley Nuclear Plant in Alabama, focusing on tackling debris fretting, a leading cause of fuel leaks. According to the company, AM was essential to refining the design, reducing the size of debris that could enter the reactor, and achieving a 30% increase in debris resistance.
Speaking with 3D Printing Industry, experts from Oak Ridge National Laboratory (ORNL), the largest energy research lab in the U.S., explained how 3D printing benefits nuclear energy. Professors Xin Sun and Kathy McCarthy shared that AM enables the production of advanced reactor components, such as fuel assembly brackets and channel fasteners, which improve performance, safety, and reduce costs.
They noted that 3D printing not only simplifies manufacturing and cuts R&D time but also supports smart components that incorporate sensors and AI for safer nuclear operations. While regulatory bodies were working to catch up with this new manufacturing paradigm at the time, ORNL licensed its 3D printing method to Ultra Safe Nuclear Corporation (USNC), helping to expand 3D printing adoption in the nuclear sector.
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Featured image shows Samuel Sheckman, a mechanical engineer, left, and Danny Cai, a senior engineer, with the 3D model of the top of the toroidal field coil. Photo via PPPL.
