Antares raises $470M to build nuclear reactors for the US military

Nuclear power startup Antares Nuclear said Monday that it has raised $470 million to build small reactors for U.S. military bases.

The Series C round, which was led by Paradigm and Caffeinated Capital with participation from Industrious Ventures, Point72 Ventures, and Shine Capital, underscores investors’ growing interest in advanced nuclear startups — a trend fueled by an AI data center building boom and demand for new sources of power. The Series C round included $370 million in equity and $100 million in debt.

Antares has been developing a small modular reactor (SMR) capable of producing between 100 kilowatts and 1 megawatt of electricity, enough to power up to 750 homes. 

Like many other advanced nuclear startups, Antares’ reactor uses TRISO fuel, which encapsulates uranium in carbon and ceramic shells. TRISO has been touted for years as a safer alternative to traditional nuclear fuel. The billiard ball-sized spheres of TRISO fuel can be cooled by gases like helium or molten salts. The coating is designed to prevent the fuel from melting in typical high-temperature reactors. 

Antares’ demonstration reactor, the Mark-0, reached criticality on June 4 at the Idaho National Laboratory.

The company is one of three finalists in the Pentagon’s Advanced Nuclear Power for Installations program, which will test SMRs on Air Force bases in Colorado and Montana. Antares aims to bring its first electricity-producing reactor online next year, with deployments at U.S. military installations planned for 2028.

Investors have been flocking to nuclear power, and fission in particular, as electricity demand surges in response to data center construction and the broader electrification of the economy. In April, X-energy raised $1 billion through an IPO, while Radiant Energy, Standard Nuclear, and Last Energy have each raised nine-figure rounds since December.

Antares closed its last round, a $96 million Series B, also in December. Altogether, Antares has raised $604 million, based on a TechCrunch analysis of PitchBook data.

Despite investor excitement, advanced nuclear startups face several hurdles to commercialization, including an immature supply chain in the U.S. and challenges with scaling production. Many SMR startups tout the benefits of mass manufacturing, claiming it will significantly reduce costs. But the benefits of mass manufacturing typically take at least a decade to materialize, and no startup has reached that stage yet.

The first SMRs, which are expected to enter service in the early 2030s, are unlikely to be cost competitive with most new power plants. Lazard, which analyzes the cost of energy for a variety of technologies, expects new SMRs to cost about $214 per megawatt hour. At that price, they would cost more than all but the most expensive gas turbines.

Antares hasn’t disclosed its pricing. But given the realities of the market, it’s not surprising that the startup decided to chase contracts for the U.S. military, a famously price-insensitive customer.