advanced-nuclear
(3)
Apollo Atomics
Apollo Atomics is a Cambridge, Massachusetts nuclear startup building the most power-dense pressurized water reactor. By redesigning the steam generator - the bulkiest part of a conventional plant - into a proprietary Compact Steam Generator, the company shrinks a proven reactor design by roughly an order of magnitude, turning a decade-long construction project into a factory-built machine that fits on a truck and deploys in under 24 months. Founded by MIT nuclear PhD Assil Halimi and operator Drew Walker, Apollo is in Y Combinator's Spring 2026 batch and is testing its design in collaboration with MIT.
Jordan Bramble
Jordan Bramble is the co-founder and CEO of Antares Nuclear (Antares Industries), a Torrance, California company building factory-produced, transportable fission microreactors of up to 1 MW for defense, remote industrial, and space applications. A systems engineer and physicist who did a stint in federal policy at the White House Office of Management and Budget, Bramble started Antares in 2023 on a contrarian bet: instead of chasing the commercial grid on price, sell nuclear's unique capability to customers who need power where the grid and diesel can't reach. Under his leadership Antares raised more than $130 million, built out a 145,000-square-foot factory, and in June 2026 became the first private company to bring an advanced reactor - its Mark-0 - to criticality under the U.S. Department of Energy's Reactor Pilot Program. His stated ambition is to make energy abundant 'from Earth to the Asteroid Belt.'
The Nuclear Company
The Nuclear Company is a U.S. nuclear infrastructure platform building a standardized fleet of large reactors using proven, already-licensed designs. Rather than inventing new reactor technology, it applies a 'design-once, build-many' methodology layered with AI and digital-twin software to cut the cost and timeline of building gigawatt-scale nuclear power. Founded in 2023 by Jonathan Webb, Kiran Bhatraju, and Patrick Maloney, it has raised about $70M to evaluate sites for an initial 6-gigawatt fleet targeted for the early 2030s.