Fluxnium says the ocean holds 50,000 years or so of nuclear fuel

The U.S. wants to triple its nuclear power plant capacity by 2050, but that goal could stall if plant operators can’t secure fuel at reasonable prices. Yellowcake, a form of unrefined uranium, is up 75% over the last five years, according to the U.S. Energy Information Administration, and the country has few domestic uranium resources — unless you count the ocean, which holds more than 4 billion metric tons of dissolved uranium, enough for roughly 50,000 years of supply.

Clean tech startup Fluxnium says it has cracked the problem of extracting that seawater uranium economically, using technology developed at U.S. Department of Energy national labs. “It’s like a thousand times more than all identified hard rock mines combined,” founder and CEO Jeff Green told TechCrunch. The startup, which had been working in stealth, recently closed a $7 million seed round led by Congruent Ventures, with Active Impact Investments and Constellation Energy — which operates the largest nuclear fleet in the U.S. — also participating.

Fluxnium is emerging as the U.S. nuclear industry undergoes a renaissance, with tech companies backing several nuclear startups in search of new electricity sources for their AI data centers. Green, a repeat founder who previously helped launch Stamps.com in 1996, desalination startup NanoH2O in 2005, and carbon-removal startup 1PointFive in 2020, argues the geopolitics of uranium supply make the timing right: two-thirds to three-quarters of the West’s uranium comes from Kazakhstan, Uzbekistan, Russia, Namibia, Niger, and China, he said, and rising nuclear demand, he added, could leave the West unable to meet its own uranium needs domestically.

Fluxnium’s process uses specially made polymer fibers, with chemistry licensed from the Department of Energy, that attract dissolved uranium. When first demonstrated at a national lab, the technology could extract uranium at more than $200 per pound — over twice the price Western suppliers charge today — but increasing the fibers’ surface area has let Fluxnium pull more uranium per line and bring costs down. In practice, braided fiber lines are hung off buoys at sea, similar to seaweed farming, left for 30 to 60 days, then brought ashore and purified into yellowcake without toxic tailings; each line can be reused several times.

Why it matters

If Fluxnium’s economics hold up at scale, seawater extraction could ease a looming uranium supply crunch just as AI-driven demand for electricity pushes utilities and tech companies toward new nuclear capacity.