MIT spinoff and Y Combinator-backed company is building the next generation of pressurized water reactors. Substantially oversubscribed seed round accelerates testing, manufacturing and regulator commercial approval.
CAMBRIDGE, Mass., Aug. 20, 2026 — Apollo Atomics, an MIT spinoff building the next generation of pressurized water reactors (PWRs), today announced $31 million in seed financing to commercialize a nuclear platform designed to be manufactured at scale rather than constructed as a one-off megaproject. The Y Combinator-backed company will use the capital to expand demonstration and long-duration reliability testing, build manufacturing capacity and advance its regulatory work with the U.S. Nuclear Regulatory Commission (NRC).
The round was oversubscribed and led by FCVC. Participants included Y Combinator, Telesoft Partners, Alumni Ventures, Robinhood Ventures, Nucleation Capital, Pelion VC, and Duke Capital Partners. Notable individual investors included Evan Meagher, Paul Graham, Philip Johnston, Matteo Franceschetti and Ray Rothrock.
The defining constraint of the next industrial era may not be compute or manufacturing capacity. It is the ability to reliably and timely power its infrastructure. Data centers, manufacturers and utilities are planning around electricity needs that today’s grid and project timelines are not built to meet. Nuclear power can provide around-the-clock carbon-free energy, but conventional plants are typically delivered as bespoke construction projects with long delivery timelines.
Rather than replace the light water, commercial-grade low-enriched uranium fuel and established supply chains that underpin decades of reliable and safe PWR operating experience, Apollo redesigned the largest and most complex component in the nuclear steam system: the steam generator. The company’s proprietary compact steam system is designed to deliver an order of magnitude higher power density than conventional designs. Apollo says that advancement can reduce the overall reactor footprint by roughly 40 times, enabling its high power output design to be factory-built, transported by truck and deployed in less than 24 months.
Apollo was founded by Assil Halimi, an MIT Nuclear Engineering Ph.D. with extensive experience in reactor operations and advanced PWR design, and Drew Walker, a hard-tech founder and former White House director. The company has built and tested a working reactor-system demonstrator within MIT’s Department of Nuclear Science and Engineering to expand experimental validation of its hardware under prototypic commercial reactor conditions.
Apollo is also advancing its commercial regulatory pathway. The company submitted a regulatory engagement plan to the NRC earlier this year and is seeking NRC authorization by the end of 2026 for commercial use of the fuel configuration selected for its reactor, which has already achieved criticality at full power. By using commercially available fuel, established suppliers and familiar PWR materials and operating principles, Apollo aims to reduce the technology, supply-chain and licensing risk that has slowed many advanced-reactor programs.
Apollo is developing three reactor systems: the 10-megawatt electric A-10, the 50-megawatt A-50 and the 300-megawatt A-300. The portfolio is designed to serve data centers, industrial facilities, utilities and other large energy users. Apollo reports more than 20 gigawatts of signed letters of intent in its commercial pipeline.
The financing will support construction of Apollo’s next demonstration facility, the A-1 (a 1-megawatt commercial demonstrator); long-duration reliability testing; vertical integration of key manufacturing processes; expansion of engineering and operations capabilities; and continued engagement with the NRC. Apollo’s advisory board includes former NRC Chairman Christopher Hanson, investor Ray Rothrock, MIT professor Koroush Shirvan, utility leader Mike Rencheck, and other senior utility executives.
About Apollo Atomics
Apollo Atomics is an advanced reactor company developing compact pressurized water reactors designed to accelerate nuclear deployment. Built on more than 15 years of MIT research and testing, the company’s core breakthrough is a proprietary compact steam supply system that delivers approximately an order of magnitude higher power density than conventional designs, allowing Apollo to dramatically shrink the reactor while maintaining the same power output. The resulting reactor platforms are designed to be factory-built, transported by truck, and deployed in less than two years using commercially available fuel, established supply chains, and existing regulatory pathways. Apollo is developing 10 MW, 50 MW, and 300 MW electric reactor platforms for data centers, industrial facilities, utilities, and other large energy users. Learn more at https://www.apolloatomics.com/.
SOURCE Apollo Atomics
