Antares series c raises $470 million for military microreactors

Antares series c funding has reached $470 million, giving the Torrance, California nuclear fission startup new capital to scale a military microreactor program tied to a U.S. government deadline. The round includes $370 million in equity and $100 million in debt, with Paradigm and Caffeinated Capital co-leading.

Point72 Ventures, Shine Capital and Industrious Ventures also joined the financing. Antares said the raise takes its total capital secured to more than $600 million since Jordan Bramble and Julia DeWahl founded the company in 2023. The company did not disclose a valuation.

The money is intended to support engineering, manufacturing expansion and deployment work across Antares facilities in California, Idaho and South Carolina. Antares says it plans to build its first electricity-producing Mark-1 reactor in 2027, followed by initial U.S. military deployments in 2028.

What is Antares building for the military?

Antares is developing compact, factory-made nuclear microreactors meant to provide power for military bases without relying on the civilian electric grid. The company has focused on the Department of Defense as its first market rather than pursuing utility procurement cycles.

That focus lines up with Executive Order 14299, which requires the Defense Department to have an advanced nuclear reactor operating at a domestic military installation by Sept. 30, 2028. Antares says its 2028 deployment plan includes U.S. Air Force and Army installations.

The near-term technical marker is the Mark-1, the company’s first planned power-producing reactor. Antares has not yet generated commercial electricity, and the company’s announcement did not say how much capacity the initial installations would provide or how its debt financing is structured.

Why did investors fund Antares now?

The raise follows a milestone for the company’s Mark-0 microreactor at Idaho National Laboratory. Antares said the system reached zero-power criticality under the Department of Energy’s Reactor Pilot Program, using HALEU fuel in a sodium heat pipe-cooled core. The company said the test validated reactor physics, instrumentation and reactivity control.

Antares and Paradigm describe the Mark-0 result as the first private advanced reactor criticality in the U.S. in more than 40 years. Paradigm managing partner Alana Palmedo said the firm is backing Antares as it moves from demonstration work toward microreactors intended to run for years on U.S. military bases. Caffeinated Capital partner Varun Gupta pointed to Antares’ technical choices and defense-first customer strategy as reasons for the investment.

Bramble framed the financing as capital for the shift from criticality to commercialization. According to Antares, its planned reactors are intended to operate safely for more than six years at U.S. military installations starting in 2028.

How does Antares compare with other nuclear startups?

Antares is entering a well-funded advanced nuclear field. Oklo, chaired by Sam Altman until its 2024 public listing, had a market capitalization near $13 billion as of December 2025. Radiant has raised several hundred million dollars for portable reactors positioned as diesel replacements.

Other companies are chasing different first markets. X-energy raised $700 million in a round led by Amazon’s Climate Pledge Fund. TerraPower is developing its Natrium reactor program in Wyoming with U.S. Department of Energy backing. Last Energy raised $100 million with a plan to sell small reactors into AI data centers.

Grand View Research estimated the global small modular reactor market at $6.2 billion in 2024 and projected it would reach $13.7 billion by 2030. For Antares, the test is narrower and sooner: converting a criticality milestone and $470 million of new funding into electricity at military sites before the federal deadline arrives.

This story draws on original reporting from TechFundingNews.