Radioecological consequences of radioactive releases due to weapons-grade plutonium production at the 'Mayak' facility in the Russian Federation.

The process of nuclear weapons production from 1949 to 1987 was accompanied by the generation of a great amount of radioactive waste. Waste processing operations and controls on discharges at this time were not to the same standard as today. Because of this, vast areas of the Urals region of Russia surrounding the Mayak Production Association (MPA) were exposed to routine and accidental radioactive contamination. The greatest contribution to the contamination was gas aerosol emissions from the MPA in the 1950s (total activity 38 PBq, mainlyI), releases of liquid radioactive waste into the Techa River from 1949 to 1956 (total activity 115 PBq, including long-livedSr andCs) and accidental atmospheric releases as a result of the thermochemical explosion of the storage tank for liquid radioactive waste in 1957 (74 PBq, relatively short-lived radionuclides being the main contributors). Protective measures helped to relieve the pressing problem of population safety in the 1950s and 1960s, but they led to the appearance of new sources of contamination in the territory surrounding the MPA-Lake Karachay (total activity of beta-emitters 4400 PBq) and the Techa Cascade of Reservoirs (TCR; total activity 8 PBq). Owing to natural radioactive decay and rehabilitation measures, the radiation situation in the East Urals Radioactive Trace (EURT) has improved considerably over the years. Economic activity has been partially restored in these territories. Only the most contaminated territory of the East Urals Radioactive Reserve cannot be used for any economic activities up to the present day. Marked non-uniformity of radioactive contamination of the EURT and the Techa River floodplain, as well as radionuclide washout from Lake Karachay and the TCR into the underground waters and the Techa River require on-going radioecological monitoring, management and regulatory supervision.