ORNL 3D-Prints Steel Pressure Vessel to Address U.S. Forging Shortage

A 3-by-5-foot answer to a forging problem

The United States has a pressing shortage of very large forgings. The giant presses that shape massive metal parts have largely moved overseas, leaving domestic energy, defense, and aerospace industries waiting months or years for components. Oak Ridge National Laboratory and Idaho National Laboratory are testing whether large-scale metal 3D printing can bypass that bottleneck.

Their latest demonstration is a steel pressure vessel measuring roughly three feet by five feet. It was printed in July at ORNL's Manufacturing Demonstration Facility in Tennessee using a system called MedUSA. Three robotic arms, each equipped with a welder, deposited molten wire bead by bead onto a shared turntable. The result is not a certified nuclear component, but it is a working proof of concept at a scale that matters.

How MedUSA works

Wire arc additive manufacturing is exactly what it sounds like: welding robots used as a 3D printer. The MedUSA system coordinates three independent arms so their arcs do not collide while they build a part that heats and distorts as it grows. Lincoln Electric Additive Solutions provides the path-planning software and laser scanning that compares the finished component to its original design.

By 2024, MedUSA was depositing steel at about 100 pounds per hour. That speed is what makes the system interesting for industrial manufacturing rather than laboratory curiosities. The lab has already printed a 900-pound mold for a hydropower impeller and an 837-pound stainless steel canister for spent-fuel storage that survived drop and puncture testing.

The nuclear qualification gap

Printing the shape is only the first step. Nuclear pressure boundaries require long-term performance data under neutron exposure and thermal cycling. ORNL and INL are focusing on AI-driven process monitoring to verify geometry and material properties as the component is deposited. The goal is so-called born-qualified components, where the manufacturing data itself satisfies some regulatory requirements.

ASME and the Nuclear Regulatory Commission have not yet accepted process data in place of destructive testing for pressure boundaries. No printed nuclear pressure vessel has completed that approval process. The labs acknowledge this. The realistic near-term opportunity is smaller pressure hardware for microreactors and small modular reactors, not the 606-ton calandria vessels used in full-scale reactors.

Why this matters now

The U.S. wants to expand nuclear energy, but the supply chain for large metal components is a choke point. ORNL says the parts it ultimately wants to bring back onshore weigh at least 10,000 pounds each. The July vessel is only three by five feet. It is a meaningful step, but it is not the finish line. The next milestones are material testing, code work, and enough manufacturing data to prove that printed steel behaves reliably inside a reactor over decades.