RADIOECOLOGICAL MONITORING OF AGROECOSYSTEMS IN THE VICINITY OF BELOYARSK NPP

Abstract

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.

Keywords

• nuclear power plant
• radiation safety
• radionuclides
• agricultural products
• foodstuffs
• radiation control
• soil
• contamination density