US clean tech startup Fluxnium says it has developed a way to economically extract uranium from seawater, potentially unlocking a vast new fuel source as America pursues plans to triple its nuclear power capacity by 2050. The breakthrough matters because yellowcake prices have risen 75% over five years and the US has little uranium within its own borders, leaving it reliant on supplies from countries such as Kazakhstan, Russia, Niger and China, which poses growing geopolitical risk as demand from a nuclear "renaissance" driven partly by AI data centre power needs accelerates.

The ocean holds an estimated four billion metric tonnes of uranium, roughly 50,000 years' worth of supply and a thousand times more than all known hard-rock mines combined. Fluxnium, led by repeat founder Jeff Green, uses polymer fibres developed with US Department of Energy technology to attract dissolved uranium; braided lines are hung from buoys at sea for 30 to 60 days, similar to seaweed farming, then brought ashore and processed into yellowcake without toxic tailings. By increasing the fibres' surface area, the firm has driven extraction costs down from over $200 per pound demonstrated at a national lab towards levels competitive with existing mines, and it has just closed a $7 million seed round led by Congruent Ventures, with Constellation Energy among the backers.