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Relevance. The need to assess radiation risks for the main types of fish in pools that are under the constant influence of the nuclear power plants. Aim. To assess the radiation environmental risks for the ichthyofauna of cooling pools of the operating nuclear power plants, to analyze the sources and features of formation of the radiation risks at different stages of their operation. Objects: monitoring studies of radiation environmental risks for reference fish species in cooling reservoirs of the Leningrad, Beloyarsk and Novovoronezh NPP. Methods. Calculation of the exposure dose rate and quantitative assessment of the risk of exposure to technogenic radionuclides of the ichthyofauna of the cooling pools of the Beloyarskaya, Leningradskaya and Novovoronezhskaya NPPs were carried out using the international computer complex of the updated version of ERICA Tool 2.0. Results. The paper demonstrates that the radiation ecological risks for the ichthyofauna in the cooling pools of the operating nuclear power plants are caused by the combined effect of radioisotopes of the different origin. The features of the formation of the radiation risks for each pool are specific and depend on the current radiation situation. The cooling pool of the Beloyarskaya NPP is characterized by a pronounced dependence of the radiation load on the types of operating power units. The ichthyofauna experienced the greatest radiation risks during the operation of the first two power units with thermal reactors AMB-100 and AMB-200. The decommissioning of the first power units and the construction of the units with the fast neutron reactors (BN-600 and BN-800) led to a significant reduction in the radiation load on the ichthyofauna of the cooling pool. At present, the radiation risks are caused mainly by the influence of 90Sr, which is almost not discharged from the Beloyarskaya NPP into the cooling pools, but has a predominantly global origin. Therefore, the formation of the risks is more associated with atmospheric fallout of 90Sr, and not with the operation of the nuclear power plant. The radiation risks for the ichthyofauna of the Leningradskaya NPP cooling pool are caused by the combined effect of 137Cs as a result of the radiation accident at the Chernobylskaya NPP and radionuclides with induced activity (14C; 60Co; 3H 54Mn and 65Zn), the origin of which may be associated with the operation of the nuclear reactors of the NPP. The level of radiation risk for the fish fauna of the Novovoronezhskaya NPP cooling pool for 2009–2019 increased 2.2 times due to an increase in the content of 60Co in many components of the pool. As a result, 81.7% of the radiation risks in demersal fish species were formed by the influence of 60Co. It cannot be ruled out that the increase in the 60Co content in the cooling pool of the Novovoronezhskaya NPP is a consequence of radioactive contamination of the groundwater as a result of the 1985 accident. The ecological risks for the fish fauna in all cooling pools are two to three orders of magnitude lower than the maximum allowable hazard coefficient. Thus, the normal operation of the nuclear power plants does not create unacceptable radiation risks that pose a real environmental threat to the fish fauna of the cooling pools.

The influence of waste technological waters of thermal and fast reactors of Beloyarsk NPP (Russia) on the accumulation of 60Co, 90Sr and 137Cs in macrophytes and ichthyofauna of the cooling pond has been studied. Critical radionuclides, routes of their entry into the ecosystem and periods of maximum discharge of radioisotopes into the cooling pond have been determined. It is shown that the technology of electricity generation at the Beloyarsk NPP, based on fast reactors, has a much smaller effect on the release of artificial radionuclides into the environment. Therefore, during the entire period of monitoring studies (1976–2019), the decrease in the specific activity of radionuclides of NPP origin in macrophytes was 13–25800 times, in ichthyofauna 1.5-44.5 times. The maximum discharge of artificial radionuclides into the Beloyarsk reservoir was noted during the period of restoration and decontamination work aimed at eliminating the emergencies at the AMB reactors of NPP. The factors influencing the accumulation of artificial radionuclides in the components of the freshwater ecosystem of the Beloyarsk cooling pond have been determined, including: the physicochemical nature of radioisotopes, their concentration in surface water, the temperature of the aquatic environment, the trophicity of the reservoir, the species of hydrobionts.

The results of radioecological monitoring of the cooling pond Beloyarsk NPP (Russia) have been presented. The influence of waste technological waters of thermal and fast NPP reactors on the content of artificial radionuclides in surface waters and bottom sediments of the Beloyarsk reservoir has been studied. The long-term dynamics of the specific activity of 60Co, 90Sr, 137Cs and 3H in the main components of the freshwater ecosystem at different distances from the source of radionuclide discharge has been estimated. Critical radionuclides (60Co and 137Cs), routes of their entry and periods of maximum discharge of radioisotopes into the cooling pond have been determined. It is shown that the technology of electricity generation at Beloyarsk NPP, based on fast reactors, has a much smaller effect on the flow of artificial radionuclides into the freshwater ecosystem of the reservoir. During the entire period of monitoring studies, the decrease in the specific activity of radionuclides from NPP origin in surface waters was 4.3–74.5 times, in bottom sediments 10–505 times. The maximum discharge of artificial radionuclides into the reservoir was noted during the period of restoration and decontamination work aimed at eliminating emergencies at the AMB thermal reactors of the first stage of the Beloyarsk NPP.

The relevance. Pollution of ecosystems with heavy metals and arsenic is a significant anthropogenic factor that adversely affects humans and biota. In the Sverdlovsk region, where mining and processing of mineral raw materials is carried out, high levels of pollutant emissions from stationary sources, including heavy metals, are noted. The region is also characterized by multicomponent contamination of territories with artificial radionuclides. Since 1964, the Beloyarsk NPP has been in operation in the Sverdlovsk region. The long-term operation of industrial enterprises and radiation hazardous facilities increases the technogenic load on the ecosystems of the Urals. The main aim of the research is to assess the content of heavy metals and arsenic in the soils of terrestrial ecosystems in the vicinity of industrial enterprises and the Beloyarsk NPP based on environmental monitoring. Objects. In 2013 and 2019 the soils of natural (meadow) and agricultural (arable land, grassland) ecosystems of the 30-km zone of influence of the Beloyarsk NPP were studied. The content of 17 elements related to I (Pb, Zn, Cd, As, Hg), II (Mo, Cu, Ni, Co, Cr, Sb), III (Sr, Mn, V, W, Ba) hazard classes was studied in the soil cover, as well as iron. Methods. The assessment of the total content of heavy metals and arsenic in the soil was carried out in the testing laboratory of agroecology of the RIRAE (accreditation certificate RA.RU.513078). To prepare soil samples for measurements, we used the methods of «cold vapor» and «wet ashing» with a MARS-5 microwave system (CEM, USA). The elements in the samples were determined by atomic absorption and plasma emission methods of analysis. For measurements, we used an axial atomic emission (optical) spectrometer with sample atomization in inductively coupled plasma (ICP–OES) Liberty II (Varian, Australia–USA) and a KVANT spectrometer Zeta-1 with the GRG-3. Results. It is shown that for 2013−2019 the ratio of elements in the soil cover of terrestrial ecosystems in the vicinity of the Beloyarsk NPP was quite stable. According to the decrease in the total content in the soil, heavy metals and arsenic in 2019 were arranged in the following order: Fe (average − 16700 mg/kg)>Mn (879)>Ba (134)>Zn (51)>Ni (35)≥Cr ( 32)≥V (30)≥Sr (28)>Cu (21)>Pb (12,4)≥Co (11,9)>W (6,7)>Sb (2,4)>As (1,7)≥Mo (1,5)>Cd (0,2)>Hg (0,01 mg/kg). According to the total accumulation of elements in the soil, terrestrial ecosystems are in the ratio: arable land (18,7 g/kg of soil)>meadows (14,9 g/kg)>virgin land (12,6 g/kg). Such a distinction is due to differences in the content of iron in the soil, the contribution of which to the regional background is 90…95 %. A weak correlation between the content of elements in the soil and the distance from the Beloyarsk NPP (–0,44...0,29 in 2013 and –0,29...0,38 in 2019) showed the absence of significant emissions of toxicants into the environment from the nuclear power plant both as a result of its many years of work, and after the start of operation of the BN-800 reactor. Among the I hazard class pollutants accumulated in the soil, zinc dominates (contribution 76…78 %), lead is in second place (18...21 %). In II hazard class, the main soil pollutants are nickel (45…34 %) and chromium (28…30 %). In III hazard class is dominated by manganese (68...81 %) and barium (14...27 %). It is shown that in 25…63 % of soil samples in the vicinity of the Beloyarsk NPP, the gross nickel content does not correspond to the approximate permissible concentrations established in SanPiN 1.2.3685−21. In addition, in all control plots of meadow ecosystems, the maximum permissible concentration for the content of antimony was exceeded. In 2019, in 4…25 % of soil samples of arable land and meadows, a discrepancy was noted with maximum permissible concentration for manganese, and in 4…11 % of soil samples of arable land, the maximum permissible concentration for arsenic was exceeded. The levels of accumulation in the soil of a number of heavy metals also exceed the regional background of the Sverdlovsk region: for nickel in 25...63 % of soil samples of natural and agricultural ecosystems, for manganese in 10...50 % of soil samples of arable land and meadows. The greatest amount of elements (average 42 %) is accumulated in the 0−5 cm soil layer. The maximum accumulation in the upper soil horizon was noted for cadmium (62 %), arsenic (49 %), and lead (48 %), and the minimum for antimony (29 %) and manganese (28 %). According to the total stock of toxicants in the 0−5 cm soil layer, they are arranged in a row: Cd>As>Pb>Zn>Cu>Mo>Hg>Sr>Ni>Cr>V>W>Co>Ba>Sb>Mn. In deeper horizons (5−10, 10−15 and 15−20 cm) of soil the elements are distributed evenly. Compared to other technogenically-polluted regions of Russia, the results of monitoring the content of heavy metals and arsenic in the soil of the Beloyarsk NPP area show a stable ecological situation. When planning further monitoring studies, it is necessary to pay attention to the behavior of arsenic, nickel, antimony, manganese, cadmium and lead in the soil. The increased content of these toxicants in the soil can lead to their accumulation in agricultural and natural food products.

The article provides a radiation-hygienic assessment of the current state of drinking water supply sources for the population in the observation area of the the Beloyarsk NPP and the Institute of Nuclear Materials. We determined the content of natural (234U, 238U, 226Ra, 228Ra, 210Po, 222Rn, 210Pb, 228Th, 230Th, 232Th) and technogenic (3H, 14C, 60Co, 90Sr, 134Cs, 137Cs, 238Pu, 239,240Pu, 241Am) radionuclides in drinking water of tap water, water boreholes and water wells in test settlements located at different distances and directions from radiation hazardous facilities. Results of monitoring of water sources in 2012–2013 and 2019 showed the radiation safety of drinking water in the vicinity of the Beloyarsk NPP according to several criteria. Thus, the maximum levels of the gross specific alpha-activity of radionuclides in water samples were 3.9 times lower than the control level (0.2 Bq/kg), the gross specific beta-activity was 5.7 times lower than the control level (1 Bq/ kg). Over the entire observation period, none of the drinking water samples exceeded the control levels both for individual radionuclides and for the sum of the ratios of specific activities to control levels. The content of natural and artificial radionuclides in drinking water near the Beloyarsk NPP decreases in the following order: water wells > water boreholes > tap water. For the past 20 years, there was a decrease in tritium specific activity in drinking water of the Beloyarsk NPP region by 20–35%, depending on the source of water supply. It was noted that the launch of the BN-800 reactor also did not lead to an increase in the content of other artificial radionuclides (90Sr, 137Cs) in groundwater. The average annual effective dose of internal exposure of the population due to drinking water consumption in the vicinity of the Beloyarsk NPP is 0.05 mSv, according to conservative estimates – 0.07 mSv, which is below the radiation safety threshold (0.1 mSv/a) recommended by the WHO. Natural radionuclides play the primary role in the formation of the annual average effective dose for internal irradiation (98.9%) due to drinking water consumption on the considered territories. 210Po makes the largest contribution to the dose from natural radioisotopes – 43%, somewhat less is made by 210Pb – 25%. The third place in the dose formation from natural radionuclides belongs to 234U (8%), 228Ra (7%), 226Ra (6%) and 230Th (6%). The contribution of other natural radioisotopes in the formation of the internal radiation dose from drinking water consumption does not exceed 2-3%. The contribution of technogenic radionuclides to the annual average effective dose from the consumption of drinking water is negligible (about 1%). Of the technogenic components, 90Sr (60%), 3H (20%), and 241Am (12%) play the most significant role in the formation of the internal exposure dose.

The relevance. The release of artificial radionuclides into the environment during NPP operation can lead to their accumulation in separate parts of the trophic chain, which will affect the formation of radiation doses for the members of the public. Agricultural products and local foodstuffs produced near the nuclear power plant are one of the main sources of radionuclides ingestion by humans living in the NPP vicinity. The main aim of this work was to assess the current radiation situation in the vicinity of Beloyarsk NPP and Research Institute of Nuclear Materials, JSC location based on data from the developed system of radioecological monitoring of agricultural ecosystems. Objects. Monitoring studies of agricultural ecosystems were performed in 2013 and 2019 in a 30-km zone around radiation-hazardous facilities. 15 control plots on arable lands, 13 control plots on grasslands and 13 control plots on vegetable gardens in the settlements at different distances and directions from these facilities were established there. At the control plots, the dose rate was measured, samples of soil, crops, fodder, food were taken. Methods. In total, 137 samples were examined in 2013, and 94 samples – in 2019. The content of 40K, 226Ra, 232Th, 90Sr, 137Cs and 239,240Pu was assessed in the agroecosystems’ components. In agricultural and food products, 3H and 14C concentration were additionally measured. Results. It is shown that the content of 90Sr in the soil of agroecosystems located in the vicinity of radiation hazardous facilities was 4,3…7,2 Bq/kg, and concentration of 137Cs varied within 7,5…18,9 Bq/kg. The range of variation of the content of natural radionuclides was 286…432 Bq/kg for 40K, 16.1…21.7 Bq/kg – for 226Ra and 20,1…25,5 Bq/kg – for 232Th. The average content of 239,240Pu in the soil of agroecosystems was 0,13 Bq/kg with a variation of 0,07…0,25 Bq/kg. The dose rate was in the range of 0,08…0,13 μSv/h, with an average of 0,10 μSv/h. The 137Cs contamination levels of arable land varied within: 1,1…3,9 kBq/m2 in 2013 and 1,3…2,5 kBq/m2 in 2019. The range of data on the 137Cs contamination density of grasslands turned out to be wider: 1,5…4,5 kBq/m2 in 2013 and 1,6…5,2 kBq/m2 in 2019. The 137Cs contamination densities of vegetable garden soils were within 0,9…7,7 kBq/m2. The content of 40K in the crops produced in the NPP region varied within the range from 48 to 526 Bq/kg, which is determined by the species’ characteristics of plants and the characteristics of the soils where crops are grown. In fodder products, the accumulation of 40K is noted in the range of 260…543 Bq/kg, in livestock products – in the range of 18…97 Bq/kg. The specific activity of radionuclides in the grain was recorded in the ranges of 1,03…2,8 Bq/kg for 90Sr and 0,15…0,94 Bq/kg for 137Cs. The maximum levels of 137Cs accumulation were recorded in barley (0,94 Bq/kg) and were 64 times lower than the SanPiN standard. Among vegetables, potatoes and gourds, the maximum levels of the specific activity of both 90Sr (0,84 Bq/kg) and 137Cs (0,26 Bq/kg) were noted in beets in 2013, but they were below the SanPiN standards in 45 and 300 times, respectively. In cereal straw, the average content of 90Sr varied within 2,3…3,6 Bq/kg, the content of 137Cs was 0,7…2,1 Bq/kg. In the herbage, this range was 1,2…3,5 Bq/kg for 90Sr and 0,5…1,8 Bq/kg for 137Cs. The maximum levels of the specific activity of 90Sr in straw (3,6 Bq/kg) were 50 times lower than the standard for the content of this radionuclide in feeds, for 137Cs (2,1 Bq/kg) this difference was 190 times. The maximum levels of content of 90Sr in the grass (3,5 Bq/kg) were 14 times lower than the standard, and 137Cs content (1,76 Bq/kg) was almost 56 times less. In 2013 and 2019, the dynamics of the content of artificial radionuclides in milk was multidirectional: it slightly increased for 90Sr and decreased for 137Cs. However, even the maximum values of the volumetric activity of 90Sr (0,41 Bq/l) and 137Cs (0,11 Bq/l) in milk turned out to be below the boundary levels established by the SanPiN standards by 60 times for radiostrontium and 900 times for radiocaesium. The measured content of 137Cs in beef (0,12 Bq/kg) in 2019 turned out to be more than 1,5 thousand times lower than the requirements of SanPiN. It is shown that 3H and 14C in agricultural and food products accumulate to a greater extent in the feed of agricultural animals (82…255 Bq/kg), slightly less in food grains (40…82 Bq/kg). Further, milk and potatoes (10…95 Bq/kg) follow according to the degree of 3H and 14C accumulation, and to the least extent, these radionuclides are accumulated in vegetables (3…8 Bq/kg). The results of radioecological monitoring of agroecosystems showed that long-term normalized emissions from Beloyarsk NPP and JSC «Institute of Nuclear Materials» did not lead to a registered increase in the content of artificial radionuclides in soil, agricultural products and food compared to the regional radiation background. The need for further study of the patterns of 3H and 14C accumulation in agricultural and food products of the NPP location area is noted.

The research results are presented as an analysis of long-term data on the effect of gas-aerosol emissions and liquid discharges of Beloyarsk NPP and the Institute of Reactor Materials on the content of artificial radionuclides in local foodstuffs. It was noted that the distance and directions from radiation-hazardous facilities do not significantly affect the accumulation of 90Sr and 137Cs in potatoes and milk. The investigation of a wide range of foodstuffs from the private households of 23 settlements, forests, rivers, and a reservoir of the 30-km zone of the Beloyarsk NPP influence showed that the operation of the BN-800 reactor since 2016 did not lead to a registered increase in the content of artificial radionuclides in agricultural and natural foodstuffs. The maximum specific activities of 90Sr (0.84 Bq/kg) and 137Cs (0.26 Bq/kg) in root vegetables, potatoes, melons and vegetables were noted before the start of operation of the new power unit and were 45 and 300 times, respectively, lower than the current SanPiN standards. The highest content of 90Sr in milk (0.41 Bq/l) was 60 times lower than the requirements of SanPiN, 137Cs (0.11 Bq/l) was 900 times less than the permissible levels. In poultry, the specific activity of 90Sr (0.2-0.3 Bq/kg) and 137Cs (0.13-0.16 Bq/kg) has remained stable low in recent years, and the standardised content of 137Cs in beef (maximum 0.12 Bq/kg) more than 1.5 thousand times lower than the requirements of SanPiN. The highest concentration of 137Cs in wild berries, found in strawberries (1.27 Bq/kg), was 125 times less than SanPiN standards. The content of 90Sr in mushrooms was at the level of 0.1-2.5 Bq/kg, the content of 137Cs is slightly higher than - 0.6-5.8 Bq/kg. The maximum recorded specific activity of 137Cs in mushrooms was more than 80 times lower than the requirements of SanPiN. During the observation period, a decrease of up to 20% or more in the content of artificial radionuclides in samples of 5 fish species was noted; the maximum levels of 90Sr and 137Cs in it were 14 times lower than the strictest SanPiN standards (using fish for baby food). Selective radiation monitoring of foodstuffs of Beloyarsk NPP area aimed at 3H and 14C showed that the content of these radionuclides in foodstuffs was low, close to the background level. In agricultural products, 3H and 14C accumulated to a greater extent in potatoes and milk, and in natural products – in rough boletus and bream. There was noted a need to continue research on the accumulation of 3H and 14C in foodstuffs of Beloyarsk NPP vicinity.

Abstract Organic aerosol is formed in coal mines due to heat release and evaporation of organics from coal during the longwall operation. This frictional heating occurs when a metallic cutting bit strikes a rock. Thus formed organic aerosol can contribute significantly to the explosivity of methane/air atmosphere in coal mines. In this paper, the flammable limits for the methane–air mixtures with organic aerosol are determined. For this purpose, organic aerosol is synthesizes from the coal-tar pitch in a laboratory evaporation–nucleation flow chamber. Aerosol particles synthesized under laboratory conditions are aggregates consisting of small primary particles with the fractal-like dimension D f = 2.0 ± 0.1, which is close to D f = 2.1 ± 0.1 of coal mine aerosol. It is shown that the flammability of organic aerosol/methane mixture in air is in good agreement with the Le Chatelier additive principle. The lower ignition limit for the pure organic aerosol in air is 44 g/m3.

The aim of the work is the radiation-hygienic assessment of 90Sr and 137Cs content in fish of the Ob-Irtysh river system and the study of the basic laws of the radionuclides accumulation in the ichthyofauna of these rivers. To perform this task, long-term results of radioecological studies of fish from the Techa, Irtysh and Ob rivers for the period 2004-2016 were used. Fish as a food product was evaluated according to two criteria: a) permissible levels of radionuclides specific activity (SanPiN 2.3.2.1078-01); b) using the indicator of conformity В and uncertainty of its definition ΔВ (GOST 32161-2013 and GOST 32163-2013). It is shown that a higher content of radionuclides is observed in the ichthyofauna of the Techa river (1379.1 Bq/kg for 90Sr and 41.9 Bq/kg for 137Cs). On the Ob and Irtysh rivers, the average specific activity of radionuclides in fish was significantly lower and slightly changed during the surveyed area: for 90Sr in the range of 6.0 ÷ 8.1 Bq/kg (mean 6.8), for 137Cs – 0.6 ÷ 1.9 Bq/kg (mean 1.3). Assessment for compliance with radiation safety criteria using the indicator of compliance and its uncertainty (В+ΔВ) confirmed the unsuitability of use for food purposes by the radiation factor of all studied fish species from the Techa river (45÷55 >1). Fish from all other studied areas of the Ob-Irtysh river system can be used for food without restrictions (0,06÷0,53 < 1). The distribution of 90Sr and 137Cs in the ichthyofauna of the Ob-Irtysh river system part over a 2400 km is presented in the form of empirical regression models. The models describe a sharp decrease in the radionuclides specific activity in fish in the Techa and Iset rivers by two orders for 90Sr (from 2000 to 20 Bq/kg), and by one order for 137Cs (from 40 to 2 Bq/kg). With a high degree of reliability (R2>0.86 for 90Sr and R2>0.92 for 137Cs), the presence of power relationships between the content of radionuclides in the ichthyofauna and their content in water was shown, with adequacy confirmed by Fisher’s F-criteria. This can be used for a preliminary assessment of the radionuclides level in fish based on the results of measurements of the average annual concentrations of these radionuclides in water.