Antares Nuclear

Market position

Positioned as one of the better-capitalized entrants in the microreactor segment, with roughly $604M raised per a TechCrunch analysis of PitchBook data. It is one of three finalists — alongside Radiant Industries and Westinghouse — in the Pentagon's Advanced Nuclear Power for Installations program, under which the winner would work with the Air Force to have an advanced reactor operating at an installation by 2030 or sooner. Broader competitive context includes X-energy, which raised $1B in an April 2026 IPO, plus Last Energy, Radiant Energy and Standard Nuclear, each of which raised nine-figure rounds since December.

Unlike alternative-energy developers competing on cost against fossil fuels, Antares targets applications where nuclear is the preferred or only viable option — defense installations and space — rather than grid or data center markets. It claims the first criticality by a privately developed non-light-water reactor in the U.S. in over four decades, and emphasizes reactors that operate reliably for 6+ years without on-site refueling.

Technology

Fission microreactors using TRISO fuel, in which uranium is encapsulated in carbon and ceramic shells in billiard-ball-sized spheres; TRISO coatings are designed to resist melting at high temperatures, and such fuel can be cooled by gases such as helium or by molten salts. The design is non-light-water and targets 100 kW to 1 MW electrical output, factory fabrication and shipment to site, and multi-year operation (6+ years cited by the CEO) without on-site refueling. Demonstration hardware: Mark-0 (criticality, no electricity); Mark-1 (electricity-producing, targeted 2027).

Go-to-market

Direct engagement with U.S. government programs and agencies: participation in the DOE Reactor Pilot Program for the Mark-0 demonstration at Idaho National Laboratory, and competition in the DoD Advanced Nuclear Power for Installations program, which plans to test SMRs at Air Force bases in Colorado and Montana. The company cites a customer network spanning the Air Force, Space Force, Defense Innovation Unit and NASA.

U.S. defense and national-security customers (Air Force, Space Force, Defense Innovation Unit, Department of War installations), NASA and the space economy, and remote industrial assets. The CEO has stated the company deliberately targets defense and space rather than data centers.

Geography

Headquartered in Redondo Beach, California, with facilities in Torrance, California; Idaho Falls, Idaho; and Aiken, South Carolina. Demonstration work conducted at Idaho National Laboratory; planned Pentagon test deployments at Air Force bases in Colorado and Montana.

History

Founded in 2023 in Redondo Beach, California. Forge records a $66.72M Series B-1 in October 2025 at a $277.05M post-money valuation. In December 2025 the company raised a $96M Series B ($71M equity, $25M debt) led by Shine Capital with Alt Capital, Caffeinated Capital, 53 Stations and Industrious Ventures, bringing reported cumulative funding to about $130M at that time. The Mark-0 reactor achieved criticality on June 4, 2026 at Idaho National Laboratory. On July 27, 2026 the company announced a $470M Series C ($370M equity, $100M debt) led by Paradigm and Caffeinated Capital.

Risks & controversies

Reporting notes sector-wide hurdles: an immature U.S. advanced-nuclear supply chain, difficulty scaling from one reactor to many, and the roughly decade-long timeline typically required for mass-manufacturing cost benefits, which no startup has yet reached. Lazard estimates new SMRs at about $214 per megawatt-hour, more expensive than all but the costliest gas turbines, and first SMRs entering service in the early 2030s are seen as unlikely to be cost competitive. Antares has not disclosed pricing, and its concentration on a single customer segment (the U.S. military) plus dependence on program selection under the Advanced Nuclear Power for Installations competition (against Radiant Industries and Westinghouse) are notable exposures. Sources also conflict on total funding raised ($604M per TechCrunch/PitchBook vs. $474.92M per Forge), and one source misstates the Mark-0 criticality year as 2024.