- Antares has raised $470 million in Series C funding, co-led by Paradigm and Caffeinated Capital.
- It is split into $370 million equity and $100 million debt, bringing total capital raised to over $600 million.
- The capital supports scaling production for the Mark-1 electricity-producing reactor in 2027, followed by initial U.S. military installations in 2028.
The U.S. government gave itself a deadline it did not yet have the technology to meet. Executive Order 14299 requires the Department of Defense to have an advanced nuclear reactor running at a domestic military installation by September 30, 2028. No company had a working reactor capable of hitting that date when the order was signed. Antares just raised $470 million that it will be the one that does.
The Torrance, California-based nuclear fission startup has closed a Series C round of $470 million, split into $370 million in equity and $100 million in debt, co-led by Paradigm and Caffeinated Capital, with Point72 Ventures, Shine Capital, and Industrious Ventures also participating.
It brings Antares’ total funding to more than $600 million since Jordan Bramble and Julia DeWahl founded the company in 2023. Antares says the capital will fund engineering, expanded manufacturing capacity at its California, Idaho, and South Carolina facilities, and the deployment work needed to hit its 2027 and 2028 milestones.
Bramble and DeWahl started Antares on a vision that most of the advanced-nuclear industry was chasing the wrong customer. Rather than compete for slow-moving utility contracts, they positioned the company from day one as a defence-first supplier, working directly with the Department of Defense before Antares had a reactor to show for it.
Funding after historic nuclear achievement
Antares builds compact, factory-produced microreactors designed to run military bases independently of the civilian grid, rather than chasing the slower-moving utility contracts most nuclear startups pursue.
That distinction matters as U.S. grids face growing strain from AI-driven data centre demand, extreme weather, and cybersecurity risk. A microreactor that runs for years without touching a transmission line sidesteps all three, which is precisely the pitch Antares has taken directly to the Department of Defense since its founding.
Oklo, chaired by Sam Altman until its 2024 public listing, was trading at a market capitalisation near $13 billion as of December 2025. Radiant has raised several hundred million dollars across multiple rounds for its diesel-replacing portable reactors. X-energy pulled in $700 million led by Amazon’s Climate Pledge Fund, and TerraPower continues advancing its Natrium reactor programme in Wyoming with U.S. Department of Energy backing. Last Energy raised $100 million to sell small reactors into AI data centres rather than military bases.
Against that field, Antares is selling speed and specificity: a named military customer, a fixed regulatory deadline, and a reactor that, as of June 2026, has actually run.
What “first in decades” means
That reactor is the Mark-0 microreactor, which reached zero-power criticality at Idaho National Laboratory under the Department of Energy’s Reactor Pilot Program, validating its reactor physics, instrumentation, and reactivity control using HALEU fuel in a sodium heat pipe-cooled core. Antares and Paradigm are calling it the first private advanced reactor criticality in the U.S. in more than four decades.
“Antares has achieved the first private advanced reactor criticality in decades. Now the company is moving into scaled deployment of microreactors that can operate safely and reliably for years on U.S. military bases. We’re excited to back the team as they help restore U.S. energy leadership,” Alana Palmedo, managing partner at Paradigm
“Antares stands out by delivering results — not hype. Winning the race to criticality and securing customers like the U.S. Air Force reflects strong technical decisions, from reactor design and fuel selection to focusing on defence as its first market,” adds Varun Gupta, Partner at Caffeinated Capital.
Bramble frames the moment as one race finishing and a harder one starting: “We’ve moved from winning the race to criticality to the race to commercialisation. This $470 million investment allows us to scale production and deploy reactors that can operate safely for more than six years at U.S. military installations starting in 2028.”
The clock does not move
Antares plans to build its first electricity-producing Mark-1 reactor in 2027, then deliver power to U.S. Air Force and Army installations in 2028, the same year the executive order’s deadline lands.
According to Grand View Research, the global small modular reactor market was worth $6.2 billion in 2024 and is projected to reach $13.7 billion by 2030. It is also, notably, a market almost entirely concentrated in the U.S.: Tech Funding News has reported that Europe captured only around 6.2% of NATO-wide defence-tech venture funding in 2025, and nuclear microreactor capital shows an even sharper tilt toward American developers than defence tech broadly.
Antares has the capital, a named customer, and a deadline set by statute rather than a pitch deck. What it has not done yet is generate a single watt of commercial electricity. Whether $470 million and 18 months closes that gap is the question the Pentagon, and every rival microreactor developer watching the same clock, is now waiting to see answered.
