Study Estimates Thousands Of Tons Of Uranium Left Congo Embedded In Cobalt Exports

A new study published in Nature Communications estimates that thousands of tons of uranium have left the Democratic Republic of the Congo embedded in cobalt exports, almost entirely off the books of international nuclear safeguards.

Cobalt is the metal that makes electric vehicle batteries work, and the DRC supplies roughly two-thirds of the world’s supply. The region’s cobalt sits on ground that is also rich in uranium, and the two metals behave so much alike during processing that uranium ends up carried along with it. Researchers estimate that somewhere between 2,000 and 5,000 tons of natural uranium left the country this way between 2000 and 2024, embedded in ordinary cobalt shipments.

Public records show that less than 10% of that uranium was ever formally declared. Another 1,000 to 4,000 tons likely got dumped into waste piles near mining sites, in a form loose enough to leach into soil and water nearby.

Uranium and Cobalt Dissolve Together in the Same Acid Bath

Here is where the chemistry gets interesting. Miners crush the ore, then dunk it in sulfuric acid to pull out valuable metals. Cobalt and uranium happen to dissolve at almost the exact same acidity level, so they end up mixed together in the same liquid. Refineries then add lime, which makes the liquid less acidic, so unwanted metals settle out before the cobalt gets dried into a powder and shipped overseas.

Uranium does not settle out on its own. Removing it takes extra steps, like adding phosphoric acid or installing special filters, and those steps cost real money. Researchers combed through import records for 31 mining operations and found only three that consistently imported enough phosphoric acid to actually strip uranium from their output. They found no evidence that any facility had installed the other removal method at all. By 2024, only about one in five tons of cobalt ever exported showed signs that anyone had bothered to remove the uranium in it.

A Gap in Nuclear Bookkeeping

Nuclear safeguards rules are built around a simple idea: uranium buried in rock does not count until someone actually pulls it out and identifies it. That means uranium carried inside cobalt can cross a border completely unnoticed, and only shows up on paper if a refinery somewhere down the line bothers to extract and report it.

There is exactly one documented case where that happened. A chemical plant in Finland pulled uranium out of cobalt products that had come from the DRC and sold it, between 2010 and 2017. During those same years, the DRC reported exporting zero uranium. That single Finnish plant remains one of the only known instances of this uranium ever entering the official nuclear record.

Most of that cobalt, and the uranium inside it, has been headed to Chinese-owned refining companies, which dominate the global cobalt processing industry. Based on trade records, researchers estimate about 65% of the uranium ended up there. Under an agreement China has signed, the country is supposed to report any uranium imports over 10 tons a year that come from a single country without nuclear weapons, and the DRC fits that description. According to the researchers’ model, the DRC’s cobalt shipments alone would have blown past that threshold every year since 2010, and by 2024 the estimated total was more than 50 times the reporting line.

Ancient Fault Lines Fused the Two Metals Together

Cobalt and uranium did not end up together by accident. Hundreds of millions of years ago, tectonic activity fractured and folded the rock layers beneath what is now southern DRC, concentrating both metals along the same fault lines. In the richest deposits, uranium can make up as much as 3% of a cobalt-bearing crystal’s total weight, which is an extraordinarily high concentration for a metal that is usually scattered thinly through the Earth’s crust.

To pin down how much uranium moved through the supply chain, researchers combined geological maps, uranium measurements from published studies, and two decades of mine-level trade data with a chemical model of uranium’s behavior during processing. Even in their most cautious scenario, assuming every mine sat at the lowest uranium levels considered plausible, the study still found that more than 1,000 tons of uranium were likely exported.

Health Risks for Miners and Nearby Communities

Earlier studies have already found elevated uranium levels in the bodies of people living near these mines, including artisanal miners, workers, sometimes children, who dig and wash cobalt ore by hand for a living. Uranium left behind in waste piles can dissolve or spread into the surrounding environment. Miners working underground also breathe in radon, a radioactive gas released as uranium slowly decays.

Demand for cobalt has exploded alongside the electric vehicle boom, pushing DRC output past 150,000 tons a year, but oversight never caught up. In 2006, the government ordered cobalt to be exported only as refined metal rather than raw powder, a rule almost nobody follows because the country lacks enough electricity to run large-scale refineries. A separate 2002 law flagged uranium as a restricted material, but cobalt shipments still are not routinely tested or tracked for it.

Cobalt mining in the DRC has already faced years of scrutiny over child labor and unsafe conditions. This study adds a new layer to that story: the same supply chain that builds the batteries in electric cars has likely also been moving a controlled nuclear material across borders, mostly unnoticed and unreported. The researchers argue the fix is not complicated, just unglamorous: routine testing, honest reporting, safer waste disposal, and real protections for the workers digging it all up.

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Disclaimer: This article reports on findings from a single peer-reviewed study. The uranium export and tailings figures cited are model-based estimates, not direct measurements of individual shipments, and the authors describe a range of plausible values rather than a single confirmed total.

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