Apollo Atomics raises $26M seed to shrink a key nuclear component
Apollo Atomics, a Y Combinator Spring 2026 batch company, has closed a $26 million seed round to commercialize a compact steam generator that it says can shrink a nuclear reactor by a factor of 40 and cut production costs to a fifth of existing designs. The round, which included $5 million in debt, was led by FCVC with participation from 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. The funding was announced exclusively to TechCrunch on August 20, 2026.
The company, co-founded by CEO Assil Halimi and Drew Walker, is not designing a new reactor. It is rethinking how thermal energy converts into electricity by attacking the largest single component in a nuclear power plant: the steam generator. In a conventional pressurized water reactor (PWR) — the design behind roughly 80% of the world's nuclear plants — the steam generator takes heat from the reactor's primary coolant loop and uses it to produce steam that drives the turbine. These conventional steam generators are hand-built, several stories tall, and are one of the reasons reactor construction requires years of on-site fabrication.
Apollo's steam generator is about the size of a person. It threads two fluid loops through a compact block of metal laced with needle-thin channels to transfer heat more efficiently. Think of it as replacing a building-sized heat exchanger with something closer to a high-performance radiator core — the same job, done in a fraction of the volume. Because the design is suitable for mass manufacturing rather than bespoke on-site construction, the company plans to assemble the reactor and steam generator in a factory and ship the finished unit. Apollo says the approach allows it to build a reactor 40 times smaller than one using a conventional steam generator, and predicts its reactor will cost four to five times less to produce than existing designs.
The design builds on research from MIT, where Apollo has already constructed a small 40-kilowatt reactor to demonstrate the underlying technology. The company's website cites 15,000+ reactor hours of operating experience and describes its product as "the most power-dense nuclear system." Apollo also plans to offer commercial-grade nuclear fuel and supply chain services alongside its reactor design and operations.
Apollo plans three reactor sizes, ranging from 10 megawatts-electric (MWe) to 300 MWe. For context, a typical large nuclear plant today produces around 1,000 MWe, so even Apollo's largest offering is a fraction of conventional scale. The company expects to build a 300-megawatt power plant in less than 24 months, attributing the compressed timeline to labor savings and the smaller physical footprint. A demonstration reactor is planned ahead of a commercial deployment targeted for 2028.
The cost target is aggressive. Halimi projects an Apollo power plant can generate electricity at a rate of 3 cents per kilowatt hour, and the company's stated goal is to beat natural gas on cost rather than incrementally improve on existing nuclear economics. Conventional gigawatt-scale nuclear plants, as Apollo notes, take more than 10 years and roughly $20 billion per plant to build.
The broader context here is whether factory assembly and a dramatically smaller balance-of-plant footprint — everything in a power plant outside the reactor itself — can actually translate into the cost curve the company projects. The PWR lineage matters: the core reactor technology is well-understood and regulator-familiar, which reduces one category of risk. The steam generator is the novel component, and it is where the engineering claims will need to hold up under sustained thermal cycling (repeated heating and cooling) and radiation exposure. A 3-cent-per-kWh figure would put nuclear below the levelized cost of most combined-cycle gas plants, but that number is a projection from a company that has not yet built a commercial-scale unit.
The $26 million seed, even with debt included, is modest relative to the capital nuclear ventures typically require to reach demonstration. The comparison is not exact, since Apollo is not designing a new reactor core and its value proposition rests on a manufacturing and supply-chain argument rather than a novel neutronics design. But the gap between seed funding and a 2028 commercial deployment, with a demonstration reactor still ahead, leaves a substantial capital-raising trajectory between now and then.
What Apollo is proposing is narrower and potentially more tractable than a full reactor redesign. If the compact steam generator performs as described, the manufacturing and siting economics of PWR-based plants change materially. The reactor sizes on offer, from 10 MWe to 300 MWe, span both distributed and utility-scale applications, and a sub-24-month construction timeline for a 300 MWe plant would be a meaningful departure from current nuclear deployment speeds. The technology is at the demonstration stage now, and the 2028 commercial target will be the figure to watch.
