The purpose of the study was to study the patterns of forming average annual and cumulative exposure doses. The subject of the study was the dynamics of the average annual and cumulative doses of the adult population of the Russian Federation after the Chernobyl nuclear power plant accident. Results and conclusions. We estimated the contribution of external and internal exposure doses accumulated during the first year after the disaster into the total doses accumulated in 1986-2016 in the population living in the areas with different levels of 137 Cs activity in surface soil. The contribution of the exposure doses received during the first year after the accident into the total doses accumulated in 1986-2016 by the population of the regions with different levels of 137 Cs activity in surface soil was more than 30%. The contribution of the internal exposure dose received during the first year after the accident into the total exposure dose accumulated in 1986-2016 by the population exceeded that of the external dose. We predicted the average annual and cumulative exposure doses of the population until the year 2056: in 2016, the actual average annual exposure dose for the population exceeded 1.0 mSv/year only in 19 settlements of the Bryansk Region while by 2056 the number of such settlements would be null. In 2016, the average cumulative exposure dose of the population exceeded 70 mSv in 55 settlements of the Bryansk Region, the maximum being 299 mSv. According to the forecast for the year 2056, the total number of settlements in the Bryansk Region with the average cumulative exposure dose of the population equal to or greater than 70 mSv would approach 92. All these settlements are situated only in the Bryansk Region. The maximum expected value of the average cumulative exposure dose would be 374 mSv. We estimated the contribution of the population exposure dose accumulated in 1986-2016 into the exposure dose accumulated during 70 years (a lifetime dose). The contribution of the average accumulated effective exposure dose for 1986-2016 into the dose predicted for 19862056 ranged 86% to 94%. This means that the major part of the lifetime dose has been already accumulated by the locals.

The paper presents methodology of the internal dose reconstruction from I-131 and caesium radionuclides received by population of Russia after the Chernobyl accident. The direct measurements of radionuclides content in a human body were the most relevant data for internal dose reconstruction. Assessment of radionuclides intake with food products was considered as the second priority and application of radioecological models as the third priority when measurement data were absent.

The results of radiological investigations (in 2001-2002) conducted near sites of the underground nuclear explosions Crystal and Kraton-3 in the Republic of Sakha (Yakutia) are presented. The sum of the current effective internal doses from 137Cs and 90Sr (from consumption of natural products) and the external dose from 137Cs deposition was about 21 μSv y-1 for adult residents of the urban settlements Aihal and Udachny. Intake of 137Cs and 90Sr (originating from global fallout) with reindeer meat contributes ~87% to the internal dose determined. At present, the consequences of the underground nuclear explosions, conducted in the 1970s, have no influence on the technogenic exposure of the local population.

The Chernobyl accident in 1986 is one of the most large-scale radiation accidents in the world. It led to radioactive contamination of large areas in the European part of the Russian Federation and at the neighboring countries. Now, there are more than 4000 settlements with the total population of 1.5 million in the radioactively contaminated areas of the Russian Federation. The Bryansk region is the most intensely contaminated region. For example, the Krasnogorskiy district still has settlements with the level of soil contamination by cesium-137 exceeding 40 Ci/km 2 . The regions of Tula, Kaluga and Orel are also significantly affected. In addition to these four regions, there are ten more regions with the radioactively contaminated settlements. After the Chernobyl accident, the affected areas were divided into zones of radioactive contamination. The attribution of the settlements to a particular zone is determined by the level of soil contamination with 137 Cs and by a value of the average annual effective dose that could be formed in the absence of: 1) active measures for radiation protection, and 2) self-limitation in consumption of the local food products. The main regulatory document on this issue is the Federal law № 1244-1 (dated May, 15 1991) “On the social protection of the citizens who have been exposed to radiation as a result of the accident at the Chernobyl nuclear power plant”. The law extends to the territories, where, since 1991: 1) the average annual effective dose for the population exceeds 1 mSv (the value of effective dose that could be formed in the absence of active radiation protection measures and self-limitation in consumption of the local food products); 2) soil surface contamination with cesium-137 exceeds 1 Ci/km 2 . The paper presents results of calculations of the average effective doses in 2017. The purpose was to use the dose values (SGED 90 ) in zonation of contaminated territories. Therefore, the calculations have been done under the assumption that the doses were formed in the absence of active radiation protection measures and self-limitation in consumption of the local food products. The dose to population, rather than the density of radioactive contamination of soil by 137 Cs, is the most objective characteristic of the actual radiation exposure to the residents of the contaminated areas.

The present work is devoted to an analysis of the data on dynamics of 137Cs and 90Sr transfer factors in the most critical (during different time periods after the radioactive fallout) links of the food chain that are necessary for assessing current internal doses for population and for reconstruction and long-term forecast of these doses.

The present work is devoted to an analysis of the regularities of 137Cs accumulation by forest mushrooms after the Chernobyl accident and the role of physical-chemical soil characteristics and climate characteristics in the formation of radioactive contamination of mushrooms of different biological types. For the analysis of obtained results, database, containing the values of about 500 measurements of 137Cs concentration in mushroom samples was used. Aggregated transfer factor (Tag) was used as a parameter of radionuclide migration from soil to mushroom.Quantitative relationship between 137Cs Tag from soil to different species of mushrooms and soil properties was obtained as regression equations with respect to the most closely correlated parameters.

The article presents major results of the work performed by St. Petersburg Research Institute of Radiation Hygiene after Professor P. V. Ramzaev on public contracts signed within the implementation of the Federal targeted program “ Mitigation of the radiation accidents’ consequences for the period until 2015” ( Direction IV “ Streamlining of monitoring systems and their elements and situation forecasting on radioactively contaminated territories paragraph 14 “The analyses and comprehensive evaluation of radiation situation changes on radioactively contaminated territories “ aimed at compilation of radioactively contaminated zones’ settlements list and Direction VI “Awareness raising and social -psychological rehabilitation of radiation- affected residents”, paragraph 20 “Creation of unified informational system on ensuring population’s radiation safety and overcoming radiation accidents’ consequences via development of the federal and regional informational resources’ systems” and “ Joint activities program on mitigation of the Chernobyl disaster within the Union State for the period until 2016” ( Direction II “ Streamlining of unified radiation protection system in radioactively contaminated territories” paragraph 2.1 “ The harmonization of requirements, methods and technologies aimed at mitigation of Russian and Belorussian population’s internal and external exposure, the development of radiation control and monitoring unified system”, sub-paragraph 2.1.1 “The development of unified assessment and forecast system for population exposure doses and rationing of radionuclide – containing foodstuffs, agricultural products and forest preserves based on the international approaches” ) over the period from 2011 to 2015.

The article contains substantiation of criteria of return of territories with radioactive pollution caused by Chernobyl NPP accident to conditions of normal population activity. It is established that in 12 entities of the Russian Federation (except Bryansk and Kaluga regions) all agricultural food produce, including that from the personal part-time farms, corresponds to hygienic specifications. Non- corresponding to the standard SanPiN 2.3.2.1078-01 on 137Cs are part of the milk samples produced at personal part-time farms of the Bryansk region and most of natural foodstuff samples (berries, mushrooms, fish and wild animals meat) in Bryansk and Kaluga regions. The content of 137Cs both in agricultural and in wild-growing foodstuff produced at radioactively contaminated territories depends not only on the density of radioactive pollution, but also on the types of soil. The average settlement annual effective dose of population irradiation (AAED90) in the 3700 among 4413 settlements as of 2014 was below 0.3 mSv/year. Only in 713 settlements of Bryansk, Kaluga, Oryol and Tula regions the AAED90 exceeds 0.3 mSv/year. In the Bryansk region, once subject to the greatest radioactive contamination, in 276 settlements AAED90 exceeds 1 mSv/year, and in 8 of them - 5 mSv/year. The legislation of the Russian Federation defines only criteria and requirements for consideration of the suffered territories as zones of radioactive contamination. Requirements on transfer of territories polluted by radiation accidents and their population to normal life activity conditions (regarding the radiological factor) are not developed. Radiological criteria are suggested for transfer of the settlements considered to be the zone of radioactive pollution to conditions of normal life activity: average irradiation dose of critical population group: 1.0 mSv per year and lower (AAED crit); decrease of radionuclide soil contamination density to the level enabling to use the territory for traditional agricultural production meeting sanitary requirements without special measures for decrease of the 137Cs or other radionuclides content.

The Chernobyl accident in 1986 is one of the most large-scale radiation accidents in the world. It led to radioactive contamination of large areas in the European part of the Russian Federation and at the neighboring countries. Now, there are more than 4000 settlements with the total population of 1.5 million in the radioactively contaminated areas of the Russian Federation. The Bryansk region is the most intensely contaminated region. For example, the Krasnogorskiy district still has settlements with the level of soil contamination by cesium-137 exceeding 40 Cu/km2. The regions of Tula, Kaluga and Orel are also significantly affected. In addition to these four regions, there are 10 more regions with the radioactively contaminated settlements. After the Chernobyl accident, the affected areas were divided into zones of radioactive contamination. The attribution of the settlements to a particular zone is determined by the level of soil contamination with 137Cs and by a value of the average annual effective dose that could be formed in the absence of: 1) active measures for radiation protection, and 2) self-limitation in consumption of the local food products. The main regulatory document on this issue is the Federal law № 1244-1 (dated May, 15,1991) «On the social protection of the citizens who have been exposed to radiation as a result of the accident at the Chernobyl nuclear power plant». The law extends to the territories, where, since 1991: – The average annual effective dose for the population exceeds 1 mSv (the value of effective dose that could be formed in the absence of active radiation protection measures and self-limitation in consumption of the local food products); – Soil surface contamination with cesium-137 exceeds 1 Cu/km2. The paper presents results of calculations of the average effective doses in 2014. The purpose was to use the dose values (SGED90) in zonation of contaminated territories. Therefore, the calculations have been done under the assumption that the doses were formed in the absence of active radiation protection measures and self-limitation in consumption of the local food products. The dose to population, rather than the density of radioactive contamination of soil by 137Cs, is the most objective characteristic of the actual radiation exposure to the residents of the contaminated areas.

The article discusses the issues associated with the current exposure of the population of 14 regions of Russia due to the Chernobyl accident, identified tasks facing Rospotrebnadzor today. The article describes criteria and requirements for ensuring of the mechanism of the transition of settlements from the conditions of a radiation accident to the public normal conditions.

The article contains an analysis of the experience of Rospotrebnadzor radiological units’ activities for radiation safety provision of the participators and guests of XXII Winter Olympic Games in Sochi and also of Sochi city inhabitants as during the period of preparations for the Games so during the period of the Olympic and Paralympics Games. Peculiarities of organization of activities of Rospotrebnadzor specialists are considered for the preparation period and main period, the occurred problems of technical and methodical provision of radiation control which was carried out for the purpose of counteraction to possible actions of radiation terrorism are considered as well. The role is noted of the specialists of Radiation Hygiene Institute in the methodical and organizational provision of the whole complex of carried-out activities.

In the period from April 22 until May 20, 2011, an expedition aboard the research vessel “Pavel Gordienko” (Russian Federation) was carried out to the Sea of Japan and the Kuril-Kamchatka region of the Pacific Ocean. The main aim of the expedition was to study radioactive contamination of the atmospheric air and sea water after the accident at the NPP “Fukushima-1” in Japan. This paper provides preliminary results on the activity concentration of 137 Cs and 134 Cs in twenty four samples of sea water. The activity concentrations of 131 I, 137 Cs, 134 Cs, and 7 Be for twenty nine samples of atmospheric aerosols, which were sampled during the expedition, are also given. Despite the preliminary character of the results of this study, a generic conclusion on a negligible radiological impact of the anthropogenic gamma-ray-emitting radionuclides for the Far-Eastern sea areas of Russia can be reached. The investigations have been supported by a grant from the Russian Geographical Society.

Basic measures of the Rospotrebnadzor emergency response during the early stage of the «Fukushima-I» NPP radiation accident are being analyzed in the article. Radiation monitoring of the environmental objects of the territories of the Russian Federation Far East Federal District, radiation control of arriving from Japan vehicles, freights and passengers as well as imported from Japan food products were promptly organized. This allowed to get reliable evaluations of the levels of radioactive contamination at the Russian Federation territory and population exposure doses due to the «Fukushima-I» NPP accident, timely exclude the possibility of import to the Russian territory for the freights, vehicles, food products having contamination exceeding established in the Russian Federation standards.

The paper presents analysis of radiological survey data in the Far Eastern territories of the Russian Federation performed by experts of Federal Service for Surveillance on Consumer Rights Protection and Human Well-being (Rospotrebnadzor) Administrations and Federal Health Organizations Centers of Hygiene and Epidemiology of the Rospotrebnadzor in cooperation with the Saint-Petersburg Research Institute of Radiation Hygiene, in the time period from March to June 2011. The authors present preliminary assessment for contribution of the fallout carried by air currents from the Fukushima nuclear power plant in contamination of surveyed areas and population exposure doses.