Radiation situation on the territories of the Leningrad Region affected by the Chernobyl accident

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The accident at the Chernobyl nuclear power plant was the largest nuclear accident in the world. It led to radioactive contamination of 14 regions of the Russian Federation. In 1991, 4540 settlements were attributable to areas with levels of soil contamination by 137 Cs of more than 1.0 Ci/km2. As of 2016, 3855 settlements with the population of more than 1,5 million people are carried to a zone of radioactive contamination according to the Government Directive No 1074 dated October 8, 2015 «On Approval of the List of settlements located within the boundaries of the zones of radioactive contamination from the Chernobyl disaster». In accordance with this Directive, in the Leningrad region 29 settlements were classified as zones of radioactive contamination. This article describes the dynamics of changes in the radiation situation and its current state in the territories of the Leningrad Region affected by the Chernobyl accident. The paper presents the dynamics of 137 Cs and 90 Sr contents in food products of local origin, the results of calculations of the current average annual effective doses used for the purposes of settlements’ zoning, and the average annual effective radiation doses actually received by the population, dating back to 1986. According to the results of laboratory studies, since 1987, there have been no exceedances of the permissible levels for 137 Cs s in agricultural products and food raw materials of local origin. However in the wild products (mushrooms) excesses of the permissible levels for 137 Cs have been periodically detected. The cases of exceeding the permissible levels for the content of strontium-90 in food, drinking water and water from open water bodies were not recorded for the entire observation period; the determined activity was at the level of tens and hundreds of times less than the permissible levels. In 2016, conservatively estimated average annual effective doses of exposure used for the purposes of settlements’ zoning, of residents of settlements in the Leningrad region, referred to the zones of radioactive contamination, do not exceed 0.090 mSv / year. The average annual dose actually received by the population in 2016, does not exceed 0.082 mSv / year. Thus, based on the results of the radiation monitoring, the situation associated with the impact of ionizing radiation sources in the Leningrad Region, formed as a result of the Chernobyl accident, currently is characterized as safe.