City located in the southeastern Ural Mountains in Russia. In 1957, the cooling system of a radioactive liquid waste storage tank at Mayak malfunctioned and exploded. Large quantities of radioactive waste were released. The contamination spread over an area measuring approximately 100 kilometers long and 9 kilometers wide. During the 1970a, a former Soviet scientist who fled to Britain disclosed in his writing that more than 10,000 people emigrated as a result of the disaster.
After nuclear disarmament, plutonium and highly enriched uranium removed from nuclear warheads were transported to Chelyabinsk-70 from all over Russia and the city was exposed to even more radioactive contamination.