The Apollo Atomics seed round, totalling $26 million including $5 million in debt financing, is not funding a new type of reactor. It is funding a new type of steam generator, and the distinction matters more than it might first appear.
Founded in 2025 as a spinout from MIT and headquartered in Cambridge, Massachusetts, Apollo Atomics was built on a premise its founders believe the wider nuclear industry has missed: the reactor core is not the main obstacle to cheaper nuclear power. The steam generator is.
Rethinking the Steam Generator, Not the Reactor
‘We focus on the largest component, the steam generator,’ Assil Halimi, the startup’s CEO and an MIT Nuclear Engineering PhD, told TechCrunch. ‘We have been able to shrink that component and make the whole system way more compact than any other reactor in the market.’
Conventional steam generators are hand-built, several storeys tall, and borrowed almost unchanged from coal and natural gas plant designs. Apollo’s version threads two fluid loops through a compact metal block laced with needle-thin channels, transferring heat far more efficiently. The result is a generator roughly the size of a person that can be mass-manufactured rather than assembled on site.
That compactness cascades through the rest of the plant. Apollo says its reactor is 40 times smaller than one built around a conventional steam generator, and its proprietary compact steam system is designed to deliver approximately 10 times the power density of standard steam generator technologies. The company uses commercially available low-enriched uranium fuel and established pressurised water reactor supply chains, keeping it within familiar regulatory territory rather than betting on exotic fuel cycles.
Co-founder Drew Walker, a hard-tech entrepreneur and former White House director, joins Halimi in arguing that factory assembly is the unlock for nuclear economics. Because the reactor and steam generator are compact enough to build indoors, Apollo expects to complete a 300-megawatt power plant in under 24 months, at a reactor cost four to five times lower than existing designs. Halimi projects a levelised electricity cost of 3 cents per kilowatt hour. ‘Our target is to beat natural gas,’ he said.
Apollo Atomics Seed Round: Backers, Pipeline, and What Comes Next
FCVC led the Apollo Atomics seed round, with Telesoft Partners, Y Combinator, Alumni Ventures, Robinhood Ventures, Nucleation Capital, Pelion VC, Duke Capital Partners, New Era Ventures, Orange Collective, Stanford University, E14 Fund, and Neutron Power Ventures also participating. Individual investors included Paul Graham, according to Pulse2. Apollo was part of Y Combinator’s Spring 2026 batch.
The proceeds will fund expanded demonstration work, long-duration reliability testing, manufacturing capacity, and regulatory engagement with the United States Nuclear Regulatory Commission, according to Fundraise Insider. Apollo has already submitted a regulatory engagement plan to the NRC and is seeking NRC authorisation by the end of 2026 for its fuel configuration, which has already reached criticality at full power, according to Dealroom.
The company has already built a 40-kilowatt reactor at MIT to demonstrate the technology. Next in the pipeline is the A-1, a 1-megawatt commercial demonstrator planned for 2027. Beyond that, Apollo intends to offer three commercial product lines: the A-10 at 10 megawatts, the A-50 at 50 megawatts, and the A-300 at 300 megawatts, as reported by Tech Funding News.
The commercial ambition behind those sizes is underwritten by a substantial pipeline. Apollo says it has signed letters of intent for more than 20 gigawatts of intended capacity, a figure that reflects considerable appetite from buyers even before a full-scale demonstrator exists.
The scientific foundations run deep. The company draws on MIT’s Department of Nuclear Science and Engineering, which has accumulated 15 or more years of research underpinning Apollo’s compact steam generator approach. Whether that translates into NRC authorisation by year-end will be the first real test of whether the company’s timeline holds.
