The U.S. Nuclear Regulatory Commission (NRC) is investigating a chemical leak at a uranium conversion facility in southern Illinois.
According to the NRC event report (pdf), a leak of radioactive uranium hexafluoride, UF6, occurred at the Honeywell uranium enrichment plant in Metropolis at roughly 8:30 PM on Sunday. No injuries have been reported.
The plant is the only facility in the United States that converts yellowcake uranium into UF6. The chemical ultimately becomes fuel for nuclear reactors.