Lake Baikal, Siberia, Russia

After enrichment, only 10 percent of the uranium-derived radioactive material would be exported to international customers, leaving 90 percent in the Lake Baikal region for storage. Uranium tailings contain radioactive and toxic materials, which if improperly stored are potentially dangerous to humans and can contaminate rivers and lakes.
Historical traditions
The first European to reach the lake is said to be Kurbat Ivanov in 1643.