1958 Mailuu-Suu tailings dam failure
The 1958 Mailuu-Suu tailings dam failure in the industrial town of Mailuu-Suu, (Kyrgyz: Майлуу-Суу), Jalal-Abad Region, southern Kyrgyzstan, caused the uncontrolled release of 600,000 cubic metres (21,000,000 cu ft) of radioactive waste. The event caused several direct casualties and widespread environmental damage.
Source: Wikipedia — 1958 Mailuu-Suu tailings dam failure (CC BY-SA 4.0)