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 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 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 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.

During the years passed after the Chernobyl accident we are carrying out monitoring of the radiation situation in the Sough-Western territories of the Bryansk region, contaminated with the long-living radionuclides which includes 137Сs concentration measurements in agricultural and natural foodstuffs, surveys of local populations on the structure and composition of the diet accompanied with 137Сs content measurements in the human body. In the article the obtained data is systematized on the food rations of the adult population of theBryansk region, on food rations dynamics in the first and following years after the accident, which is necessary for the correct estimation of internal exposure doses of the population living on the contaminated territories.

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.

In the paper, we use the data on the content of caesium radionuclides in foodstuffs and in Bryansk region adult inhabitant’s body, on their food ration and its changes during the first years after the Chernobyl accident, and on the measures to protect the population from internal exposure. We calculate dynamics of 137Cs intake in the body and its contents therein, while maintaining a traditional diet and while replacing food products for radiationfree ones. The results show that the actual 137Cs content in the body is usually below the one calculated on the basis of the food ration. It was found out that individual 137Cs contents in the body correlate with the rate of meat, dairy and natural food products consumption and with factors of protection from internal exposure. The efficiency of the protective measures to reduce the intake and the content of caesium radionuclides in the body of inhabitants, as well as the average effective dose in the first years after the accident has been quantitatively assessed.

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.

In the beginning of the fifties planned releases of liquid radioactive wastes were performed from the radiochemical enterprise "Mayak" to the riverbed of the Techa river flowing in the area of the Chelyabinsk region. In the paper the current exposure doses of the population living in the Techa river basin were estimated. For this purpose the approach basing on the maximal use of site specific parameters that characterise external gamma field and behaviour of people in this field; concentration of Cs and Sr radionuclides in food products and consumption of food products by people was used. Parameterisation of both (external and internal) models was performed on the basis of the measurement results obtained during field expeditions. In the paper as average values of external and internal doses of inhabitants of two villages (Muslyumovo and Brodokalmak) and 5 % and 95 % percentiles in dose distributions are submitted. The contribution of external exposure to a total dose of the population varies from 40 % up to 80 % depending on the group of the population. The contribution that Sr and Cs make to the dose from internal exposure is similar. The main products determining the internal dose are fish (29-61%) and milk (11-63%). The results of dose assessment suggest that the established dose limit for population of 1 mSv per year will probably be exceeded only for the critical group in village Muslyumovo.

Four field expeditions (2001-2002) have been undertaken in the Republic of Sakha (Yakutia), Russia in order to evaluate the current radioecological status of territories affected by an accidental radioactive release from the “Kraton-3” peaceful underground nuclear explosion, carried out on the bank of Markha river in 1978. In the forest adjacent to the explosion site, 100% lethal effects to adult larches were detected over an area covering approximately 1.2 km. Elevated levels of long-lived artificial radionuclides were determined in all main compartments of the affected forest ecosystem. Maximum registered levels of Cs, Sr and Pu ground deposition were, in units of kBq m: 880, 1060 and 21, respectively, which are higher by a factor of 10 than those expected from global fallout. The content of Cs in biotic compartments is as follows (Bq g, dry weight): lichens, 1.1-220; mosses, 1.9-57; herbs, 0.04-1.2; twigs of dead adult larches, 0.29-14; needles of live young larches, 8.8. The content of Sr is as follows (Bq g, dry weight): lichens, 0.35-240; mosses, 1.9-24; herbs, 0.18-4.0; twigs of dead adult larches, 0.61-44; needles of live young larches, 4.8. The content of Pu is as follows (Bq kg dry weight): lichens, 4-1700; mosses, 17-1300; twigs of dead adult larches, 3.6-90; needles of live young larches, 23. Despite the presence of heavily contaminated environmental objects within the region, the current average effective dose from Cs and Sr to humans living in nearby settlements is 0.013-0.014 mSv y, which does not exceed the range typical for the population of other Northern Russian territories of 0.0150.180 mSv y and it is far below the officially established dose limit of 1 mSv y. The current radiological situation around “Kraton-3” site is an example for which the common postulate: “if man is protected, biota is protected as well” is clearly not valid.

Two field expeditions in 1996 studied 137Cs intake patterns and its content in the bodies of adult residents from the village Kozhany in the Bryansk region, Russia, located on the shore of a drainless peat lake in an area subjected to significant radioactive contamination after the 1986 Chernobyl accident. The 137Cs contents in lake water and fish were two orders of magnitude greater than in local rivers and flow-through lakes, 10 years after Chernobyl radioactive contamination, and remain stable. The 137Cs content in lake fish and a mixture of forest mushrooms was between approximately 10–20 kBq/kg, which exceeded the temporary Russian permissible levels for these products by a factor of 20–40. Consumption of lake fish gave the main contribution to internal doses (40–50%) for Kozhany village inhabitants Simple countermeasures, such as Prussian blue doses for dairy cows and pre-boiling mushrooms and fish before cooking, halved the 137Cs internal dose to inhabitants, even 10 years after the radioactive fallout.

The Semipalatinsk Test Site in Kazakhstan was one of the major sites used by the USSR for testing nuclear weapons for more than 40 y. Since the early 1990's, responsibility for the site has passed to the Kazakh authorities. There has been a gradual re-establishment of agricultural use such as horse and sheep farming. Therefore, it has become important to evaluate the current and future risk to people living on and using the contaminated area. Internal dose assessment is one of the main components of the total dose when deriving risk factors for population living within the test site. Internal doses based on food monitoring and whole body measurements were calculated for adults and are in the range of 13-500 muSv y(-1) due to radiocesium and radiostrontium.

Activity concentrations of 137Cs and 90Sr in samples of vegetation and natural food products collected in the Kola Peninsula in 1998 and 1999 indicate a very slow decrease in contamination levels during the last decade, mainly due to the physical decay of the radionuclides. The activity concentrations of 137Cs in reindeer meat decreased with a half-life of about 9 years. 137Cs in lichen, moss and fungi is significantly higher than in natural vegetation (grasses) and agricultural plants (potatoes). The activity concentrations of 137Cs in reindeer meat were two orders of magnitude higher than those in locally produced beef and pork. Consumption of reindeer meat, fish, mushrooms and berries constituted the main contribution to the internal dose from 137Cs and 90Sr for reindeer-breeders in the Lovozero area. The estimated committed doses due to 137Cs intake in this group were about 10μSv per month in summer 1998 and 15μSv per month in winter, 1999. There was good agreement between internal dose estimates based on intake assessment and whole body measurements. The population of Umba settlement, which is not involved in reindeer breeding, received individual committed doses due to 137Cs intake of about 0.5μSv per month, about a factor of 20 less than the reindeer-breeders in Lovozero. In this case, the main contribution to the internal dose of the general population came from consumption the of 137Cs in mushrooms and forest berries. The contribution of 90Sr to the internal dose varied from 1% to 5% in the different population groups studied.

Previous discharges of radioactivity from the Mayak Production Association plant in the Urals have resulted in considerable radionuclide contamination of the Techa River, and consequent high radiation doses during the late 1940s and 1950s to residents of villages along the Techa river. The most contaminated villages close to the site were evacuated in the period 1954–1962. The objective of this recent study was to conduct a preliminary assessment of the current radioactive contamination of soil, vegetation and foodstuffs in the two remaining villages closest to the Mayak site, Muslyumovo and Brodokalmak. The highest contamination levels in soil were found in the floodplain at 5.5MBqm−2 for 137Cs and 1.0MBqm−2 for 90Sr. Radionuclide contamination in soil of the villages was much lower, but exceeded that expected from global fallout. Data from 1207 measurements of 137Cs in milk and 1180 for 90Sr in milk for the period 1992–1999 were collated. There was no change with time in the 90Sr or 137Cs activity concentration in milk over the measured period. There were significantly higher 137Cs activity concentrations in milk sampled during the housed winter period in Muslyumovo compared with the grazing summer period, but compared to that for Brodokalmak or for either settlement for 90Sr. The highest measured activity concentrations in food products of 137Cs and 90Sr were found in river fish, waterfowl, poultry and milk. The measured activity concentrations of 137Cs and 90Sr in some animal products were higher than that expected from soil and vegetation from fields and pasture in the villages (not including the floodplain) confirming that the highly contaminated floodplains are contributing to contamination of some animal products.

Countermeasures have been effectively employed within intensive agricultural systems in areas of the Former Soviet Union (FSU) affected by the Chernobyl accident. However, ingestion doses continue to be elevated in some areas as a result of few foodstuffs which are collected from the wild or produced by the household. Forest fungi and berries, and milk from privately owned cattle are the most notable contributors to 137Cs intakes amongst these foodstuffs. In this paper we consider advice which would help affected populations to both understand the importance of these exposure routes and to reduce their exposure. In addition to the potential radiological benefits, self-help schemes are highly cost-effective and likely to have a positive psychological influence on populations living within contaminated areas of the FSU. Evidence to suggest that the transfer of radiocaesium to cow milk is considerably higher in the FSU than within western Europe and North America is discussed.