Fluxnium Raises $7 Million to Extract Uranium From Seawater

Fluxnium has closed a $7 million seed round to commercialize uranium extraction from seawater, emerging from stealth under founder and CEO Jeff Green. The round was led by Congruent Ventures, with participation from Active Impact Investments and Constellation Energy TechCrunch.

The investor mix pairs climate venture capital with a direct stake from the power industry. Constellation Energy's participation puts a nuclear operator on the cap table of a fuel supplier that has not yet operated commercially.

The core system is adsorption, not mining. Instead of digging rock, Fluxnium uses specially made polymer fibers that act like chemical sponges, attracting uranium already dissolved in seawater. The company licensed its extraction chemistry from the U.S. Department of Energy.

In operation, braided fiber lines hang from buoys at sea for 30 to 60 days before they are brought ashore for processing. Each line can be reused several times. Once ashore, the captured uranium is washed off the fibers, a step called elution, and purified into yellowcake, the powdered form that is processed into fuel for nuclear plants.

The chemistry is not new. It targets uranyl ions, the dissolved form uranium takes in seawater, by dipping plastic fibers containing amidoxime, a chemical group that binds uranium, into the water. The route was described by Stanford researchers in 2017 Stanford. Scientists have reported making five grams of yellowcake with acrylic fibers Reuters. Another U.S. effort, SuperCritical, aims to extract uranium from seawater with specially treated acrylic fibers that dissolved uranium ions stick to Reuters.

Fluxnium's deployment model borrows from marine aquaculture rather than offshore oil and gas. The company describes fiber that captures uranium deployed on longline systems in open water, rope lines held up by buoys, using the same infrastructure proven by seaweed and mussel farms Fluxnium. It developed its high-surface-area fiber, fiber designed for maximum contact with water, with a leading U.S. national laboratory and plans to produce uranium in U.S. waters for sale as yellowcake into existing utility procurement.

That procurement path matters. Yellowcake feeds established conversion, enrichment and fabrication flows, the standard steps that turn powder into reactor-ready fuel. Fluxnium does not need to invent a new reactor fuel form to find buyers.

Economics are the central technical question. In national-lab testing, the technology extracted uranium at more than $200 per pound, according to the company's disclosure of those results. Fluxnium separately projects its production costs at or below current industry average production costs. The first figure is a measured test point. The second is a forward projection for a scaled marine system.

The resource base is large. The ocean contains over 4 billion metric tons of uranium. Seawater holds roughly 1,000 times more uranium than all known land deposits combined.

The supply argument is domestic security and permitting. The United States imports more than 98% of its uranium supply, and roughly two-thirds of global production comes from countries posing geopolitical risk to supply. Permitting a new domestic uranium mine takes a decade or more, while hard-rock production costs are expected to double by 2050 as ore grades decline. Fluxnium's seawater process produces no tailings, the leftover crushed-rock waste from mining.

The broader context here is cost versus deployability. A test result above $200 per pound leaves a wide gap to close against mined uranium, even allowing for projected learning curves in fiber manufacturing, longer reuse cycles and lower marine operating costs. Adsorbent capacity per kilogram, elution efficiency and turnaround time will decide throughput. Marine operations will decide uptime.

From a buyer's perspective, the value is less about undercutting current spot supply and more about optionality. A domestic, mine-free source that slots into existing yellowcake procurement offers a hedge against concentration risk and permitting delay. That helps explain utility interest at the seed stage. Utilities rarely fund fuel research for yield.

In my view, the aquaculture analogy is the detail to watch. If longlines, buoys, handling vessels and onshore washing can ride on equipment and practices already proven at scale in seaweed and mussel farming, Fluxnium avoids building a bespoke offshore industry from zero. Reuse is doing heavy lifting in that model. Fiber lines that survive several 30- to 60-day soak and wash cycles spread both capital cost and marine logistics over more pounds produced.

Looking over the longer arc, optimism is warranted, with caveats. Seawater uranium has been a laboratory curiosity for decades because the ocean is dilute and the chemistry is slow. Moving it toward industrial production will require sustained engineering on durability, selectivity and process integration rather than a single breakthrough. If Fluxnium can drive demonstrated costs down toward its projected range while operating in U.S. waters, it would give reactor operators something they lack now, a scalable domestic feed that produces no tailings and avoids a decade-long mine permit.