Leveraging more than $140 million in private capital fundraising, over 322,000 square feet of operational manufacturing space, and multifaceted partnerships with the Departments of Energy and Defense, reactor start-up Antares has become the first company involved in the Reactor Pilot Program to achieve zero-power fueled criticality—a full month ahead of the July 4 deadline set by President Trump’s Executive Order 14301.

This milestone, announced yesterday, was achieved with the company’s Mark-0, a forerunner to the R1, which is the company’s flagship design. The R1 is a sodium heat-pipe-cooled, TRISO-fueled microreactor. The Mark 0 is distinct from the R1 in that it is configured for zero-power criticality testing and as such is equipped with neither power conversion nor heat removal systems.

For Antares, this development represents a key validation of its reactor physics, control systems, and supply chain.

Advanced nuclear energy start-up Antares has announced the close of a $96 million Series B funding round, led by Shine Capital with participation from Alt Capital, Caffeinated, FiftyThree Stations, Industrious, and other investors. The round raised $71 million in new equity capital and $25 million in debt for equipment, factory build-out, and uranium procurement.

The Department of Energy made conditional commitments yesterday to provide high-assay low-enriched uranium to three companies: reactor developer Antares Nuclear; fuel fabricator Standard Nuclear; and Natura Resources, which is backing Abilene Christian University’s development of a small Molten Salt Research Reactor and pursuing a commercial reactor design of its own. Following a contracting process, some of the companies “could receive their HALEU later this year.”