Antares

Antares (Antares Nuclear, Inc.) is a nuclear fission energy company developing compact, factory-produced microreactors intended to supply power for defense installations, space missions and underwater applications. Its lead product, the R1 microreactor, is described as modular and transportable, delivering 100 kWe to 1 MWe for six or more years. The design uses TRISO coated particle fuel in a prismatic graphite core, graphite and boron carbide control drums with independent actuator motors, sodium heat pipes for passive high-temperature heat transfer, a fin-and-tube primary heat exchanger, a recuperated closed nitrogen Brayton power conversion cycle operating below 300 psi, and a power management and distribution node able to connect to local microgrids. An integrated shielding and transport cradle is intended to simplify field deployment.

The company positions itself as vertically integrated, with in-house capabilities in special-purpose reactor design and manufacture, high-temperature heat pipes and radiators, automated control systems with hardware-in-the-loop digital twins, and precision machining of nuclear-grade graphite. Reported facilities include Torrance, California; Idaho Falls, Idaho; and Aiken, South Carolina, plus a 322,000 sq ft vertically integrated R&D site called Antares Prime. One secondary source instead describes a 145,000 sq ft production facility and roughly 60 employees, and gives conflicting founding years (2023 versus 2025), so facility and headcount details are inconsistent across sources.

Antares states a staged roadmap: 2025 conceptual design review, an approved Nuclear Safety Design Agreement, testing of an electrically heated demonstration unit, submission of a preliminary documented safety analysis and a HALEU fuel allocation; 2026 first reactor demonstration at Idaho National Laboratory under the Department of Energy Reactor Pilot Program (initial criticality of the Mark-0 microreactor); 2027 operation of a full-power, electricity-producing Mark-1 reactor; and 2028 initial customer deployments."/* */

Founding story

Secondary reporting states Antares was founded in 2023 by co-founders Jordan Bramble, who serves as CEO, and Julia DeWahl [4][6]. No further founding narrative is provided in the sources.

Business model

Antares designs and manufactures its own reactors using a vertically integrated supply chain and in-house manufacturing, selling or deploying factory-built microreactor power systems to government and defense customers; reported funding sources include venture capital and government contracts [0][2][3][6].

Sources do not describe pricing or revenue mechanics; funding is reported as a combination of venture equity, debt and government contracts [3][6].

Traction

Reported milestones include completion of a conceptual design review, an approved Nuclear Safety Design Agreement, submission of a preliminary documented safety analysis, testing of an electrically heated demonstration unit, a HALEU allocation and start of fuel fabrication, opening of the 322,000 sq ft Antares Prime R&D facility, and initial criticality of the Mark-0 microreactor at Idaho National Laboratory in 2026 under the DOE Reactor Pilot Program [0][3][4].

Latest developments

In July 2026 Antares announced a $470M Series C co-led by Paradigm and Caffeinated Capital, comprising $370M equity and $100M debt, weeks after its Mark-0 reactor reached criticality at Idaho National Laboratory — described as the first privately developed non-light-water reactor to achieve criticality in the United States in more than 40 years. Proceeds are earmarked for the Mark-1 electricity-producing reactor in 2027 and initial defense deliveries in 2028 [2][3][4].