Assil Halimi's Apollo Atomics raises $26M to shrink nuclear's steam generator

Why it matters

Apollo Atomics is testing whether nuclear developers can cut cost and construction time by preserving familiar reactor technology and redesigning one oversized bottleneck. Its 2027 demonstrator will put that claim against real hardware.

Assil Halimi and Drew Walker's Apollo Atomics has closed a $26 million seed round, including $5 million in debt, TechCrunch reported on August 20th. FCVC led the financing, with Telesoft Partners, Y Combinator, Alumni Ventures, Robinhood Ventures, Nucleation Capital, Pelion VC, Duke Capital Partners, New Era Ventures, Orange Collective, Stanford University, MIT's E14 Fund and Neutron Power Ventures participating.

Halimi has spent years studying the economic problem Apollo Atomics is trying to solve. The Algerian-born engineer first became interested in nuclear power after seeing uranium's energy density during a college internship, according to an MIT profile. He studied electrical and nuclear engineering alongside mathematics and economics in France before completing doctoral research at MIT on reactor design, fuel performance, thermal hydraulics and the economics of small modular reactors.

Walker brings a different operating history. He previously co-founded electric-boat developer Blue Innovations Group, worked on manufacturing and operations in electric vehicles, and served in the White House. Apollo Atomics is pairing Halimi's reactor research with an operator whose background centers on moving physical products from designs into production.

That pairing matters because Apollo Atomics is making a manufacturing bet disguised as a reactor design. Halimi is preserving the familiar pressurized-water reactor stack, including light-water cooling, commercial low-enriched uranium and established nuclear supply chains. His technical gamble is concentrated in the steam generator, a large heat exchanger that transfers energy from a reactor's primary coolant loop to the steam system that drives a turbine.

A person-sized answer to a building-sized component

Conventional steam generators use large assemblies of tubes and can rise several stories. Apollo Atomics routes the primary and secondary fluids through narrow channels inside a compact metal block. The smaller channels increase the surface area available for heat transfer, allowing Apollo Atomics to reduce the component's volume.

Apollo Atomics says its compact steam generator is about the size of a person and one-twentieth the size of a conventional generator with the same thermal output. Halimi told TechCrunch that the redesign makes the complete reactor system roughly one-fortieth the size of a comparable system built around a conventional steam generator.

Both figures remain Apollo Atomics projections. Their commercial importance comes from what the smaller hardware could remove from a project: custom construction, large structures, on-site assembly and years of labor exposed to schedule overruns. Apollo Atomics plans to manufacture reactor and steam-generator units in factories and transport them to deployment sites.

The Apollo Atomics product roadmap includes the 10-megawatt A-10, the 50-megawatt A-50 and the 300-megawatt A-300. Apollo Atomics is pitching those systems to data centers, industrial facilities and utilities, three customer groups facing rising demand for round-the-clock power.

Halimi told TechCrunch that Apollo Atomics is targeting electricity at 3 cents per kilowatt-hour and expects a 300-megawatt plant could be built in less than 24 months. He also projected that the reactor would cost four to five times less to produce than existing designs. "Our target is to beat natural gas," he said.

That is an aggressive benchmark. Apollo Atomics' target depends on factory output, financing, licensing and construction all working at a pace the nuclear industry has rarely sustained.

The old nuclear stack is the point

Advanced-reactor developers have frequently redesigned the fuel, coolant and reactor core together. Those choices can improve performance, but they also introduce new supply chains and larger bodies of evidence for regulators to assess.

Apollo Atomics is taking the narrower route. Pressurized-water reactors already have decades of commercial operating history, while conventional low-enriched uranium avoids dependence on specialized fuels required by some advanced designs. Halimi's thesis is that nuclear economics can improve through one high-impact component without rebuilding every layer of the system.

That idea follows directly from his academic work. In 2023, Halimi told MIT that shrinking a reactor without improving its technical design could sacrifice the economies of scale enjoyed by larger plants. His research focused on power density as a way for smaller reactors to compensate. Apollo Atomics applies that logic beyond the core: move the same thermal power through much less equipment, then build the equipment repeatedly in a factory.

Apollo Atomics says it has built a 40-kilowatt reactor at MIT as a demonstrator. A 1-megawatt demonstrator is planned for 2027, followed by the first commercial deployment targeted for 2028.

In April, Apollo Atomics announced a research collaboration with MIT's Department of Nuclear Science and Engineering. The work covers primary- and secondary-loop testing under conditions intended to represent commercial operation, including two-phase flow and heat-transfer performance. Apollo Atomics said the results would validate computational models and support its Nuclear Regulatory Commission pathway.

The NRC lists Apollo Atomics among advanced-reactor developers that have notified the regulator of plans to engage. Apollo Atomics said in April that it was targeting a construction permit application in 2028. TechCrunch's report places the first commercial deployment in that same year. Those milestones leave Apollo Atomics with a compressed regulatory and construction schedule, even before accounting for first-of-a-kind manufacturing.

The round buys a test of the thesis

The seed financing gives Apollo Atomics capital to move from a small demonstrator toward the 1-megawatt system planned for 2027. That step should produce the operating and manufacturing evidence needed to test Halimi's central claims about compactness, cost and deployment speed.

Apollo Atomics also advertises 20 gigawatts of signed letters of intent in its commercial pipeline. Letters of intent measure customer interest rather than completed projects. Converting that pipeline will require Apollo Atomics to turn a compact heat exchanger into a licensable power plant with a financeable construction plan.

The restraint in Apollo Atomics' architecture is the strongest part of Halimi's pitch. He is asking regulators, suppliers and customers to accept one concentrated engineering change while keeping much of the nuclear system familiar. Walker's job is to make that restraint translate into repeatable manufacturing rather than another bespoke plant.

The $26 million round funds the point where that argument meets hardware. A person-sized steam generator is a compelling image. Apollo Atomics still has to prove that shrinking the component can also shrink nuclear power's licensing, financing and construction burden.