Holtec Delivers Critical Component for Revolutionary US Fusion Reactor

Holtec International has achieved a remarkable feat - the fabrication and delivery of the Centre Stack Casing (CSC) for the Princeton Plasma Physics Laboratory's (PPPL's) National Spherical Torus Experiment-Upgrade (NSTX-U), a revolutionary step towards commercial nuclear power based on nuclear fusion. This magnificent piece of engineering represents the heart of the NSTX-U, which is expected to produce high-performance plasma with low-cost magnetic fields.

The Centre Stack Casing for the NSTX-U (Image: Holtec)

The CSC had to be designed and manufactured with extremely precise tolerances to meet the demanding metrology and magnetic permeability requirements. This challenge demanded Holtec's weld engineers to develop and qualify several unique welding procedures and tools that were then implemented by their highly skilled machinists and welders. The final product, which is made of inconel metal and resembles a hedgehog due to its stud-covered design, will provide the inner vacuum wall of the NSTX-U and structural support for plasma-facing components and coils that must withstand temperatures of up to 10 million degrees Celsius.

PPPL Lab Director Steve Cowley describes the CSC as a "beautiful piece of inconel metal" that is "magnificent" and "well-travelled," having been forged in Italy, machined in New Jersey, and assembled in Pittsburgh. Its arrival marks a significant project milestone and will enable important recovery work to begin.

Holtec's Director of Weld Technology, Brian Farnsworth, expresses immense pride in the team's dedication and diligence to produce this critical component. He notes that fabricating something of this caliber required expertise and weldments of the highest quality. "This is a true testament to what Holtec's manufacturing organization can achieve," he adds.

Holtec's Chief Strategy Officer, Fritz Roegge, believes that this project demonstrates the company's ability to leverage its state-of-the-art human and industrial capability to support emerging energy technologies such as fusion and to support US government customers.

The NSTX-U is the flagship fusion facility at the US Department of Energy's PPPL. Unlike conventional tokamaks, the spherical device is shaped more like a cored apple and can produce high-pressure plasmas with relatively low-cost and cost-effective magnetic fields. Its three main objectives are to explore the facility's capability to produce stable, high-performance plasmas with low-cost magnetic fields, to develop the understanding and tools required to start up and sustain such plasmas non-inductively, and to develop techniques to handle and control the waste heat from fusion reactions.

Holtec's remarkable achievement in the fabrication and delivery of the CSC represents a significant step towards a future of clean, safe, and sustainable nuclear fusion energy.

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