Less than two years after the company’s site plan was approved, employees of Commonwealth Fusion Systems will soon begin moving into their new corporate headquarters and manufacturing facility on its 47-acre Devens campus on Hospital Road.
While the opening in December of the 164,000-square-foot office and manufacturing complex will bring a new influx of workers to a site already swarming with hundreds of construction workers and subcontractors, the impact of the opening will eventually be felt far beyond Devens and the region. In a second nearby structure, the company will assemble and test a device it believes could be the first to demonstrate that nuclear fusion can be a safe, carbon-free, and economically viable source of energy.
A bird’s-eye view of the manufacturing space in the new 164,000-square-foot office and manufacturing complex. (Photos by Lisa Aciukewicz)
Game changer
The standing joke about fusion energy is that it is always 30 years away. But within the past few years, the commercial viability of fusion power has suddenly seemed within reach.
What has made the difference are breakthroughs in materials research and computing that are enabling fresh approaches to the technologies that national and international projects have pursued for decades. And the urgency of lowering carbon emissions to combat climate change has energized the race to harness fusion as a carbon-free power source.
Commonwealth Fusion Systems, a 2018 spinoff of MIT’s Plasma Science and Fusion Center in Cambridge, with which the company continues to collaborate, has married one of those breakthroughs to a half-century-old technology in its design for a compact fusion device named ARC. Commonwealth scientists believe an ARC device could generate 200 megawatts of electrical power, enough to provide electricity to 33,000 or more American households. (See “Fusion, tokamaks, and ARC” on page 5.) If such devices could be manufactured economically in quantity, they would provide a carbon-free replacement for aging gas and coal-fired power plants.
The legacy technology employed by ARC is the tokamak, a fusion device that works by using powerful magnets to confine a plasma of hydrogen isotopes—deuterium and tritium—to a doughnut-like shape, or torus, forcing them to fuse, releasing energy in the process.
The breakthrough technology that sets Commonwealth’s tokamak apart from previous implementations is a new kind of magnet made from ribbons of high-temperature superconducting materials that CFS has demonstrated can produce much stronger fields than the conventional superconducting magnets used by other projects, including ITER, the internationally funded tokamak being built in France. The magnets are seen as a game changer by industry experts, and success would put Devens on the map as “the birthplace of the commercial fusion industry,” CFS Director of Public Affairs Kristen Cullen told the Press on a recent tour of the facility.
No lack of investors
Having raised more than $2 billion from private investors as of this fall, Commonwealth Fusion Systems is one of the best-funded firms racing to harness fusion as a power source. Cullen says the money will go toward completing the Devens campus and building a test version of Commonwealth’s ARC tokamak, named SPARC. Some of the investment will be spent finding and preparing a site for the first commercial installation of an ARC-powered electrical generator.
CFS has also received support from the federal Department of Energy, an enthusiastic proponent of partnerships between privately funded companies and national laboratories. Through its INFUSE program, the agency provides grants of between $50,000 to $500,000 to private-public collaborations seeking answers to engineering and scientific questions critical to making fusion devices work. CFS has been awarded 16 INFUSE grants since late 2019 when the program began.
But construction of the company’s first ARC lies in the future. First comes SPARC, the experimental fusion device with which the company will validate its approach to fusion and test potential fixes to the many engineering challenges that have prevented fusion devices from achieving net energy.
SPARC will be built a short distance from the manufacturing facility and office complex where its magnets will be assembled. As you round the northeast corner of that facility, the core of SPARC’s future home rises before you: a square, five-story concrete structure that resembles a 16th-century English pele tower. Identified as Building 2 on site plans, the structure rises from a village-like collection of construction trailers, its walls encased in scaffolding, a crane at its side, scores of workers below. But unlike a medieval pele, built by wealthy families in northern England to fend off marauding Scots, the 6- to 8-foot thick walls of Building 2, are meant to contain the energetic neutrons generated by the fusion of hydrogen isotopes deuterium and tritium—the process Commonwealth scientists have chosen to power ARC devices.
SPARC will weigh an estimated 1,000 tons, 2½ times the mass of a Boeing 747 at takeoff. According to spokesperson Cullen, reenforcing the floor that supports it required 100 tons of rebar, the mass of a large dinosaur. In addition to SPARC itself, the building will include the equipment and instruments needed to operate, monitor, and maintain it, as well as operations and work stations that will be manned periodically for parts of the work day. Ancillary buildings on the 147,000-square-foot CFS-2 site will provide cooling, storage, and other support.
On target for 2025
Cullen says that CFS is on target to complete construction of SPARC—which began in May 2021—by 2025. If testing is successful and CFS engineers and scientists can solve myriad known problems, the company hopes to have one of its ARC devices generating electricity on an electric grid somewhere on Earth by the early 2030s. A successful installation would pave the way for the manufacturing of ARC-powered electric generators by mid-century.
The opening of the facility will add to the economic impact that the redevelopment of Devens has already had on the region. According to public affairs director Cullen, Commonwealth Fusion Systems employs 350 workers, but the company continues to collaborate with MIT and the combined team numbers more than 500 people. At its website (cfs.energy/careers) CFS lists nearly 100 job openings, from engineers and IT professionals to manufacturing technicians, buyers, and administrators. “We are growing very quickly and expect to have nearly 500 employees by early next year,” Cullen told the Press. Many current and future staff will be located full time at Devens, but others will have hybrid positions that combine remote and in-person work.
CFS is building an experimental tokamak—a fusion device that uses a new generation of powerful magnets—named SPARC in Devens. CFS hopes to validate its approach to fusion and test potential fixes to the many engineering challenges that have prevented fusion devices from achieving net energy.
Although there is parking for up to 300 workers, the CFS site application approved by the Devens Enterprise Commission in January 2021 envisions that employees will add 100 trips to rush hour traffic in the morning and evening. Cullen says the company plans to offer daily private bus service between the MBTA’s Alewife station in Cambridge and the Devens campus. Some workers may use commuter rail and the shuttle service that MassDevelopment provides between the Ayer station and Devens. “Our goal has always been to encourage public transportation, our private bus service, and carpooling to reduce car trips as much as possible,” says Cullen. Truck traffic in and out of the site is expected to be minimal, DEC environmental planner Neil Angus told the Press.
From the second floor of the office wing, it’s possible to look down onto the manufacturing floor where the 18 high-temperature superconducting SPARC magnets will be assembled. Office windows on the north side of the building offer a compelling view of the structure that will house SPARC, rising, fortress-like, amid its construction. It’s a view the company seems ready to share with its neighbors. “We want to be part of the community,” says Cullen, who was recently voted a member of the Devens Jurisdiction Framework Committee to represent—along with Odile Smith of Bristol-Myers Squibb—the interests of Devens businesses.
Does the rush to commercialize fusion feel like a competitive race? Cullen said the real race is the one to replace the use of fossil fuels in time to prevent the worst effects of climate change. “If there are a couple of companies that can make [fusion] work, that would be a good thing.”
Fusion, tokamaks, and ARC
Fusion, the power that drives the sun and stars, combines light elements in the form of plasma—the hot, charged state of matter composed of free electrons and atomic nuclei —to generate massive amounts of energy. Scientists have been seeking to replicate fusion on Earth for more than a half century. The most promising device is the tokamak, first demonstrated in Russia in the 1950s.
A tokamak uses powerful magnets to confine plasmas to a doughnut-like shape, or torus, forcing the nuclei to fuse. When the plasma consists of the nuclei of the hydrogen isotopes deuterium and tritium, the product of their fusion is a helium nuclei, a neutron, and an abundance of energy. An estimated 150 tokamaks have been built worldwide since their invention, but none has been able to sustain a fusion reaction for any length of time, and none has been able to deliver more energy than it takes to operate the device.
A tokamak at heart
ARC, the fusion device that Commonwealth Fusion Systems hopes to someday commercialize, is a tokamak, but it uses a “high-temperature” ytterbium barium copper oxide superconducting tape for its magnetic coils. These coils can operate at 100 degrees Kelvin, or about minus 280 degrees Fahrenheit, which allows them to be cooled by liquid nitrogen, unlike the coils of a typical fusion reactor which must typically be cooled to minus 450 F. The coils that will be used by CFS not only operate at higher temperatures, but produce more powerful magnetic fields, allowing an ARC to be smaller than a conventional tokamak. Commonwealth Fusion’s use of these new coils is what sets the company’s approach apart from others that have taken up the fusion challenge.
Unlike fission, which produces radioactive waste and requires elaborate containment technologies to operate safely, fusion produces only medical-grade waste and is not subject to the kinds of failure that led to meltdowns at Chernobyl and Fukushima. A loss of power or leaks in a tokamak cause the device to shut down and cool instantaneously, according to a memo CFS provided the Devens Enterprise Commission with its application.
Deuterium is plentiful, but tritium is rare and radioactive, with a relatively short half-life of 12 years. Some worry that world supply of tritium is smaller than may be needed to sustain a commercial fusion industry in coming decades, as Science Magazine warned in its June 24 issue. CFS scientists and engineers, however, hope to use the neutrons generated in an ARC to breed tritium by bombarding the lithium blanket that will line its interior. ARC will employ a novel blanket design that uses a molten lithium salt as both the tritium-breeding material and a coolant. In its memo to the Devens Enterprise Commission, CFS wrote that it will require a small inventory of tritium on site, no more than 10 grams, or about the mass of two quarters. Tritium requires special handling, the company noted, and a license from the Massachusetts Radiation Control Program.
—John Osborn
