The area has also been severely damaged by the plutonium-producing facility Mayak opened in Chelyabinsk-40 ( later called Chelyabinsk-65 , Ozyorsk ) , in the Southern Ural , after World War II . Its plants went into operation in 1948 and , for the first ten years , dumped unfiltered radioactive waste into the Techa River and Lake Karachay . In 1990 , efforts were underway to contain the radiation in one of the lakes , which was estimated at the time to expose visitors to 500 millirem per day . As of 2006 , 500 mrem in the natural environment was the upper limit of exposure considered safe for a member of the general public in an entire year ( though workplace exposure over a year could exceed that by a factor of 10 ) . Over of land were contaminated in 1957 from a storage tank explosion , only one of several serious accidents that further polluted the region . The 1957 accident expelled 20 million curies of radioactive material , 90 % of which settled into the land immediately around the facility . Although some reactors of Mayak were shut down in 1987 and 1990 , the facility keeps producing plutonium
1957 accident
Kyshtym disaster
Ural Mountains