ORNL and A.J. Tuck 3D Print a Nuclear Mandrel That Leaks Nothing

A three-step process closes a supply chain gap

Oak Ridge National Laboratory and A.J. Tuck Company have combined three manufacturing methods into one continuous flow that produces leak-free containers for advanced nuclear reactor components. The process starts with a 3D printed mandrel, coats it through electroforming, then finishes with hot isostatic pressing. The result is a near-net-shape part that previously required multiple suppliers and weeks of lead time.

The mandrel is the internal form used to shape the final vessel. Getting it right matters: any flaw in the mandrel transfers to the finished part, and in nuclear applications even microscopic leaks are unacceptable. By 3D printing the mandrel directly from digital data, the team eliminated the machining step that traditionally dictated the supply chain.

Why domestic forging capacity is the bottleneck

Large pressure vessels for next-generation reactors have long depended on forging capacity concentrated outside the United States. That created lead times of months and added geopolitical risk to domestic reactor builds. The ORNL and A.J. Tuck process removes the forging step entirely.

The team demonstrated the workflow at the Manufacturing Demonstration Facility in Knoxville. After signing a license agreement, the partners are moving toward commercialization with suppliers already expressing interest in scaling the method for production pressure vessels.

What hot isostatic pressing adds

Hot isostatic pressing bonds the electroformed metal to the mandrel and closes internal porosity. It is the same step used in aerospace and medical implant manufacturing, but applying it to a 3D printed mandrel as the substrate is new. The combination means the final component inherits the dimensional accuracy of the printed mandrel and the density of forged metal.

For the nuclear industry, the practical win is speed. A part that took months to source from overseas forges can now move through a domestic digital workflow in weeks. That matters as the U.S. builds out the supply chain for small modular reactors and microreactors.