We are proud to announce that Holtec International has completed the fabrication and delivery of a critical component needed for the U.S. Department of Energy’s Princeton Plasma Physics Laboratory’s (PPPL) research into commercialization of nuclear fusion. The Center Stack Casing (CSC) will lie at the heart of PPPL’s National Spherical Torus Experiment-Upgrade (NSTX-U), a precursor to commercial nuclear power premised on nuclear fusion. 

Center Stack Casing (CSC) Staged Horizontally at Holtec Manufacturing Division in East Pittsburgh, PA

The fusion reactor must produce high performance plasma with low-cost magnetic fields which required the CSC to be designed and fabricated with exceedingly tight tolerances to meet exacting metrology and magnetic permeability requirements. The CSC will provide the inner vacuum wall of the NSTX and structural support for plasma-facing components and coils that must endure a 10-million-degree Celsius thermal environment.

Key to the success of this effort was the close partnership between PPPL and Oak Ridge Technologies, a joint venture between Holtec International and Gilmartin Engineering Works, which enabled the final design of this unique component to be matured iteratively. The challenging design demanded Holtec’s weld engineers to develop and qualify many unique welding procedures and tools to meet PPPL’s requirements. Those procedures and tools were then rigorously implemented by Holtec’s highly skilled machinists and welders qualified and certified under our internationally acclaimed Quality Assurance Program.  

“To fabricate something of this caliber required expertise and weldments of the highest quality. I am immensely proud of our team’s dedication and diligence to produce this critical component which in our initial review appeared to be almost unachievable. This is a true testament to what Holtec’s manufacturing organization can achieve,” said Brian Farnsworth, Holtec Director of Weld Technology.

“This beautiful piece of inconel metal — which I fondly call ‘the hedgehog’ due to its stud-covered design — will hold the center magnet of our flagship experiment, NSTX-U,” said Professor Steve Cowley, Lab Director at PPPL. “The casing is not only magnificent, but well-traveled: It was forged in Italy, machined in New Jersey, and assembled in Pittsburgh. Its final arrival to us at the Lab was a significant project milestone and will allow us to begin important recovery work.”

“This project demonstrated Holtec’s ability to leverage our state-of-the-art human and industrial capability beyond our core commercial fission reactor technologies to support emerging energy technologies such as fusion and to support U.S. government customers,” said Holtec’s Chief Strategy Officer, Vice Admiral (retired) Fritz Roegge.