Uranium in cobalt-hydroxide exports from the Democratic Republic of the Congo.

The Democratic Republic of Congo (DRC)'s Copperbelt is the world's leading source of cobalt, a metal essential to the energy transition. In this region, uranium co-occurs with oxidized cobalt ores. Despite no officially reported uranium production, we show that uranium is extracted, concentrated, and exported via the DRC cobalt supply chain. This conclusion follows from co-mineralization, similar behavior of cobalt and uranium in hydrometallurgical circuits, and the partitioning of uranium into crude cobalt hydroxide, the export form for over 95% of DRC production. We combine a first-order carryover model with geological mapping, mineralization and geochemical data, as well as mine-level trade records (2000-2024) to quantify these flows. We estimate 2,000-5,000 tonnes of natural uranium were exported embedded in cobalt-hydroxide shipments. Less than 10% of this material has been publicly declared and placed under international safeguards. In addition, 1,000-4,000 tonnes were likely discarded to tailings in easily-mobilized forms, posing environmental and health risks. Together, these findings identify a substantial gap in nuclear accountancy and environmental oversight within a critical mineral supply chain.