Fluxnium Raises $7 Million Seed to Extract Uranium From Seawater

Fluxnium, a clean-tech startup that emerged from stealth this month, has raised $7 million in a seed round led by Congruent Ventures, with participation from Active Impact Investments and Constellation Energy, the nuclear utility giant. The round funds a technology aimed at one of nuclear power's oldest supply-chain problems: where the uranium comes from.

The company has developed polymer fibers designed to pull dissolved uranium directly out of seawater and convert it into yellowcake, the processed form of uranium ore used to fuel nuclear reactors. The underlying chemistry was originally developed at United States Department of Energy laboratories; Fluxnium's contribution has been engineering how those fibers are manufactured and deployed at a scale that could make ocean-sourced uranium cost-competitive with conventional land-based mining. In practice, the fibers are formed into long braided lines and suspended from ocean buoys, a setup similar to commercial seaweed farming. Left in the water for 30 to 60 days, the fibers absorb dissolved uranium before being hauled back to shore, where the captured material is stripped off and purified.

The scale of the resource Fluxnium is targeting is the reason the idea has drawn attention well beyond typical clean-tech circles: the world's oceans are estimated to hold roughly 4 billion tons of dissolved uranium, an amount researchers have said could theoretically supply global nuclear fuel needs for tens of thousands of years, far exceeding known land-based reserves. Whether ocean extraction can be made economically viable at that scale remains the open question the seed round is meant to help answer.

Founder and CEO Jeff Green is a repeat entrepreneur in resource-extraction technology, having previously helped launch postage-technology company Stamps.com in 1996, desalination startup NanoH2O in 2005, and carbon-removal company 1PointFive in 2020. Constellation Energy's participation as a strategic investor is notable in its own right: the utility operates the largest fleet of nuclear reactors in the United States and has a direct commercial interest in a more diversified, domestically sourced uranium supply chain as reactor demand grows alongside AI-driven electricity consumption.

For founders in energy and deep tech, Fluxnium's raise is a useful data point on how much strategic utility capital is now flowing toward unconventional fuel-supply technologies, not just reactor design or generation itself. Nuclear power has drawn renewed investor interest through 2026 as AI data centers push electricity demand higher, and utilities with existing reactor fleets have strong commercial reasons to diversify away from a global uranium mining supply chain concentrated in a handful of countries. A domestic, ocean-based extraction method, even one that remains years from commercial-scale economics, gives a strategic backer like Constellation Energy a hedge against future fuel-supply disruption that a purely financial investor would be less likely to prioritize.

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