Apollo Atomics shrinks the steam generator to cut nuclear power costs

Nuclear power startups have raised significant funding to develop advanced reactors aimed at lowering costs, but recent projections suggest those reactors are unlikely to be cost-competitive anytime soon. Apollo Atomics founders Assil Halimi and Drew Walker think that’s because companies have been chasing the wrong problem — so instead of designing a new reactor, Apollo is rethinking how thermal energy converts into electricity by shrinking the steam generator, the largest component in a power plant.

“We focus on the largest component, the steam generator,” Halimi, the startup’s CEO, 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.” While most steam generators are hand-built and several stories tall, Apollo says its version can be mass-manufactured and is about the size of a person, which the company says has allowed it to build a reactor 40 times smaller than one using a conventional steam generator.

Apollo’s generator threads two fluid loops through a compact block of metal laced with needle-thin channels, a design meant to transfer heat more efficiently than conventional generators, which run reactor coolant through large tubes surrounded by water. Halimi said existing designs borrow heavily from coal and natural-gas power plants despite those fuels having far lower energy density than nuclear fuels like uranium, leaving current generators converting only a small fraction of the potential in their fuel source.

To build a demonstration reactor ahead of a planned commercial deployment in 2028, Apollo recently closed a $26 million seed round that included $5 million in debt, the company told TechCrunch exclusively; the design is based on research from MIT. Halimi projects an Apollo power plant can generate electricity at 3 cents per kilowatt hour, and says the company’s target is to beat natural gas rather than make incremental improvements to nuclear. Because the generator is compact, Apollo plans to assemble the reactor and steam generator in a factory rather than on site, and Halimi expects the company can build a 300-megawatt power plant in less than 24 months, at four to five times lower production cost than existing designs. Apollo has already built a small, 40-kilowatt reactor at MIT to demonstrate the technology, and plans to offer three sizes ranging from 10 megawatts-electric to 300 megawatts.

FCVC led the funding 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 participating. Apollo was part of Y Combinator’s Spring 2026 batch.

Why it matters

If Apollo’s compact, mass-manufacturable steam generator holds up outside the lab, it targets the cost driver that has kept small modular reactors from competing with natural gas — rather than adding yet another reactor design to an already crowded field.