Population exposure in the Urals occurred as a result of failures in the technological processes at the Mayak plutonium facility in the 1950s. Construction of the Mayak facility began in 1945 and was completed in 1948. Initially this complex consisted of three main parts: Reactor plant, radiochemical facility, and waste-management facilities. The major sources of radioactive contamination were the discharges of 2.7 x 10{sup 6}Ci of liquid wastes into the Techa River (1949-1956); an explosion in the radioactive waste storage facility in 1957 (the so-called Kyshtym Accident) that formed the East Urals Radioactive Trace (EURT) due to dispersion. of 2 x 10{sup 6}Ci into the atmosphere; and gaseous aerosol releases (about 560,000 Ci of {sup 131}I in total) within the first decades of the facility`s operation. The significant portion of activity for the Techa River and EURT consists of long-lived radionuclides, mainly {sup 9O}Sr. These releases resulted in the long-lived contamination of surrounding territories. The predominant radionuclide for operating gaseous aerosol releases was short-lived {sup 131}I resulting from reprocessing of nuclear fuel. The maximal annual rates, which occurred in 1952-1953, were reconstructed on the basis of technological records by the Mayak team.