Commonwealth Fusion Systems (CFS) reached a significant milestone on Tuesday morning, announcing the installation of a crucial component in its SPARC demonstration reactor.
The newly installed component is a 24-foot-wide, 75-ton stainless steel structure that serves as the foundation of the tokamak—the doughnut-shaped core of a fusion reactor. CFS aims for this reactor to be the first of its kind to produce more energy than it consumes. Known as the cryostat base, the part was manufactured in Italy and transported across the globe to CFS’s facility in Devens, Massachusetts.
“This is the first component of the actual fusion machine,” said Alex Creely, director of tokamak operations at CFS, in an interview. Construction at the site has been ongoing for over three years, focusing on developing the infrastructure and machinery needed to support the reactor’s core.
“This is a significant milestone for us, as it marks a shift in the project from constructing an industrial facility—though that work continues—to assembling the actual tokamak,” he said.
CFS is among the numerous startups that have emerged in recent years to develop fusion power, a technology that aims to generate gigawatts of clean electricity using hydrogen fuel sourced from seawater. With energy demands surging due to the rise of electric vehicles and data centers, investors are banking on fusion as a key solution for the future.
Backed by Bill Gates’ Breakthrough Energy Ventures and other investors, CFS is regarded as one of the leading contenders in proving the commercial viability of fusion power. In December, the company revealed that its first commercial-scale reactor will be built near Richmond, Virginia.
SPARC is slated to go live in 2027, and if it performs as CFS expects, it could become the first tokamak to generate more power than it consumes. To date, only the Department of Energy’s National Ignition Facility has achieved scientific break-even, accomplishing this milestone in a series of successful experiments, beginning in December 2022.
However, the NIF’s reactor operates quite differently from CFS’s approach. It relies on lasers to compress a fuel pellet to achieve fusion conditions, whereas CFS’s tokamak uses powerful magnets to contain and control plasma heated to 100 million degrees Celsius, shaping it into a tight doughnut-like form until fusion is initiated.
Tokamaks rely on superconducting magnets to create the intense magnetic fields necessary to contain the plasma. These magnets must be cooled to -253 degrees Celsius using liquid helium. The cryostat plays a crucial role in maintaining these ultra-cold conditions by acting as an insulator, much like a thermos. “The cryostat base is essentially the bottom of the thermos,” Creely explained.
Similar to unboxing an Amazon package, CFS had to unpack and inspect the cryostat base before installation. However, unlike a typical e-commerce delivery that takes seconds to open, the process for CFS spanned several days to remove the shipping materials, followed by an additional week to thoroughly check for any potential damage during transit, Creely explained.
The CFS team then transported the cryostat base to the tokamak hall, where carefully positioned bolts extended from the concrete foundation, ready to secure the stainless steel disk. “Then you grout it in,” Creely explained.
In addition to the cryostat base, work is progressing on the remaining three major components of the tokamak, which will be assembled together into their final configuration either later this year or early next year. Following assembly, CFS will conduct a thorough commissioning process to ensure all components function as intended, a phase that will take several months.
“This is a one-of-a-kind system,” Creely said. “It’s not as simple as just pressing a button to turn it on.”
