America wants to triple its nuclear power capacity by mid-century, but that ambition depends on a steady supply of affordable uranium. Fluxnium, a startup that has just stepped out of stealth, believes the answer has been sitting in the ocean all along.

Nuclear power is enjoying a revival in the United States. Big tech companies hungry for electricity to run AI data centers have poured money into a wave of reactor startups, and policymakers have set aggressive expansion targets. Yet the fuel side of the equation has received far less attention.

Yellowcake, the unrefined form of uranium that feeds the supply chain, has climbed roughly 75% in price over the past five years, based on federal energy data. On top of that, the U.S. has few meaningful uranium deposits of its own, leaving reactor operators reliant on imports.

Founder and CEO Jeff Green points to a deeper worry: for Western buyers, the bulk of global uranium comes from places such as Kazakhstan, Uzbekistan, Russia, Namibia, Niger and China, which introduces real geopolitical risk. If demand grows as forecasts suggest, he argues, the market will face a structural shortage.

Seawater holds more than 4 billion metric tons of uranium, enough to fuel reactors for around 50,000 years. By Green's estimate, that is roughly a thousand times the uranium in every identified hard rock deposit combined. The catch has always been cost: pulling such a dilute resource out of the ocean economically has eluded researchers for decades.

Fluxnium licensed a uranium-attracting polymer chemistry developed at U.S. Department of Energy national labs, then focused its own work on how the fibers are produced and arranged. Its central insight was boosting the fibers' surface area so they capture far more uranium per pass.

When the method was first demonstrated at a national lab, recovered uranium cost upward of $200 per pound, more than double what Western suppliers currently charge. Fluxnium says its higher surface-area fibers pull more uranium from the water, which lowers that figure substantially.

The biggest remaining expenses sit in manufacturing the fibers and deploying them at sea. Green stresses that no individual step in the process is new; the company's job is to squeeze cost out of each stage until ocean uranium can compete head-to-head with traditional mines.

Fluxnium recently closed a $7 million seed round led by Congruent Ventures, joined by Active Impact Investments and Constellation Energy, the operator of America's largest nuclear fleet. Having a major reactor owner on the cap table signals real industry interest in a domestic fuel source.

Green is no newcomer to spotting big shifts. He previously helped launch Stamps.com, desalination company NanoH2O and carbon removal venture 1PointFive, and he now sees uranium as the next major opportunity.