Jordan
Bramble

In June 2026, a machine roughly the footprint of a shipping container quietly split its first atoms in a test bay at Idaho National Laboratory. No cooling towers. No skyline of steam. Just a microreactor called Mark-0 humming to life - and with it, Antares Nuclear became the first private company to bring an advanced reactor to criticality under the U.S. Department of Energy's Reactor Pilot Program.

The man who set the deadline for that moment, and then hit it, is Jordan Bramble. He is the co-founder and chief executive of Antares, a company he started in 2023 with a stubborn idea: that the future of nuclear energy would not be built for the power grid at all.

Most reactor companies chase the same dream - cheaper electrons for the utility next door. Bramble looked at that race and walked the other way. Antares builds factory-produced fission microreactors of up to one megawatt, designed to run where the grid has never reached and diesel is a liability: remote defense bases, off-grid industrial sites, the surface of the Moon.

The bet is less about physics than about customers. Bramble identified buyers who don't care what a kilowatt-hour costs on a spreadsheet - they care whether the lights stay on when there is no line to plug into. The Department of Defense. NASA. Miners at the end of the road. For them, resilient power is not a commodity. It is the whole game.

That reframing is why Antares moves at a pace the nuclear industry rarely sees. The company raised more than $130 million, stood up a 145,000-square-foot factory in Torrance, California, and runs a build-and-test loop measured in days, not decades. Bramble is not waiting for permission to iterate. He is iterating until the permission becomes obvious.

Bramble did not arrive at fission the usual way. He studied physics and statistics at Georgetown and systems engineering at George Mason - a combination that reads less like a career plan and more like a toolkit for someone who intends to build something complicated and sell it too.

Before Antares, he worked inside the machinery of the federal government, at the White House Office of Management and Budget. It is a strange launchpad for a hardware founder. But it taught him something most reactor engineers never learn: how the state actually decides where money and urgency go. When your first customers are the Department of Defense and NASA, that fluency is not a footnote. It is an unfair advantage.

He founded Antares in 2023, on the coast south of Los Angeles, and assembled a team that borrows its DNA from the fastest-moving corners of hard tech - alumni of SpaceX, MIT, Rigetti Computing, and the U.S. Air Force. The blend is deliberate. Nuclear brings the rigor; the newcomers bring the refusal to accept that things must take forever.

Then he did the thing founders talk about and rarely do: he set a hard, public deadline. Antares would take a low-power test reactor critical before July 4, 2026. In an industry where schedules slip by years, that was either bravado or a promise. In June 2026, Mark-0 went critical at Idaho National Laboratory - the first private advanced reactor to do so under the DOE pilot. The promise held.

The money followed the milestones. In December 2025, Antares closed a $96 million Series B - $71 million in equity and $25 million in debt - led by Shine Capital, with Alt Capital, Caffeinated Capital, FiftyThree Stations, and Industrious joining in. The debt was earmarked for the unglamorous but decisive stuff: equipment, factory build-out, and uranium procurement. Bramble is fond of pointing out that a supply chain hollowed out by decades of industry stagnation has to be rebuilt part by part, and he is doing exactly that across three states - Torrance, California; Idaho Falls, Idaho; and Aiken, South Carolina.

What comes next is the hard part: a full-scale, electricity-producing demonstration unit targeted for 2027. Criticality proves the physics. Electrons prove the business.