The Promise of Nuclear Fusion Energy
Site Visit Summary
Commonwealth Fusion Systems
Devens, Massachusetts
Friday, November 21, 2025 | 12:00 PM – 2:00 PM
Tour Hosts
Kristen Cullen – Vice President of Global Policy and Public Affairs (Employee #8) LinkedIn
Lilly Blumenthal – Public Policy LinkedIn
Attendees
- Rep. Erica Layon – Executive Departments and Administration
- Rep. Greg Sargent – Resources, Recreation & Development
- Rep. Gregory Hill – Legislative Administration (Chairman)
- Rep. JD Bernardy – Science, Technology & Energy
- Rep. John Schneller – Science, Technology & Energy
- Rep. Jordan Ulery – Ways & Means; Co-Chair ALEC-NH
- Rep. Keith Ammon – Commerce
- Rep. Lisa Post – Commerce
- Rep. Michael Vose – Science, Technology & Energy
- Rep. Rick Devoid – Criminal Justice and Public Safety
- Riley Glaser – Student
- Rep. Rita Mattson – Science, Technology & Energy
- Rep. Tanya Donnelly – Resources, Recreation & Development
- Thomas Barrasso – NH Department of Energy
- Sen. Tim McGough – Commerce; Economic Development Administration
- Rep. Tony Caplan – Science, Technology & Energy
- Rep. Vanessa Sheehan – Legislative Administration
Visit Structure
The two-hour visit included an introductory presentation and Q&A (first 30 minutes), a hard-hat tour of the campus (middle hour), and a closing discussion (final 30 minutes).
Company Background
CFS was founded in 2018 as a spin-off from MIT's Plasma Science and Fusion Center, originating from a 2012 graduate class taught by Professor Dennis Whyte. The company has raised over $2 billion from investors including Breakthrough Energy Ventures, Eni, Google, and Temasek. In 2021, CFS demonstrated a 20-Tesla high-temperature superconducting magnet—a key breakthrough enabling smaller, more economical fusion reactors.
Key Discussion Topics
Design Choice: CFS uses the tokamak design—a doughnut-shaped device using magnetic fields to confine plasma at over 100 million degrees Celsius. Their high-temperature superconducting magnets allow for much smaller reactors than traditional approaches like ITER.
Location: CFS is headquartered in Devens, Massachusetts, on a former Army base (Fort Devens, 1917–1996) now operating as a special development district managed by MassDevelopment. In December 2024, CFS announced its second location: the James River Industrial Center in Chesterfield County, Virginia, where they will build the ARC commercial plant. The Virginia site, leased from Dominion Energy near a retiring coal plant, was selected after evaluating over 100 locations worldwide for its skilled workforce, grid connectivity, and growing regional energy demand.
Fusion vs. Fission: Fusion combines light atoms (releasing energy like the sun) rather than splitting heavy atoms. It produces no long-lived radioactive waste, uses abundant fuel from seawater, and poses no proliferation risk.
Fuel: CFS reactors will use a 50/50 mix of deuterium and tritium. Deuterium is a hydrogen isotope that can be extracted inexpensively from ordinary seawater—about 1 in every 6,500 hydrogen atoms in water is deuterium, providing a virtually limitless supply. Tritium is rarer and radioactive, so CFS will initially purchase it from existing sources (primarily produced as a byproduct in heavy-water fission reactors). However, the ARC design is intended to breed its own tritium: neutrons from the fusion reaction will interact with lithium in the molten salt blanket surrounding the reactor, generating tritium for future fuel supply.
Safety: Unlike fission, fusion cannot melt down. The reaction requires precise conditions to sustain—any disruption causes it to stop within seconds. Only grams of fuel are present at any time, and no chain reaction is possible.
Projects Observed
SPARC: Demonstration tokamak under construction, targeting 50–140 MW of fusion power. Operations expected in 2026, with net energy gain demonstration in 2027.
Magnet Factory: 120,000-square-foot facility producing 10-ton superconducting magnets containing 165 miles of HTS tape each. SPARC requires 18 magnets.
ARC: Planned 400 MW commercial plant for Chesterfield County, Virginia (early 2030s). Google has signed a 200 MW power purchase agreement.
Heat Transfer: ARC will use molten salt (FLiBe) to absorb fusion heat and breed tritium fuel.
Acknowledgments
The delegation thanks Kristen Cullen, Lilly Blumenthal, and the CFS team for their hospitality. We look forward to following their progress toward delivering commercial fusion energy.