Radiation situation in the area of the state scientific centre "Research Institute of Atomic Reactors" before putting a multi-purpose fast neutron reactor into operation. Part 2. Freshwater ecosystems

The analysis of the radiation survey results of freshwater ecosystems of three rivers and the Cheremshansky Bay of the Kuibyshev Reservoir in the vicinity of State Scientific Centre “Research Institute of Atomic Reactors” (SSC RIAR, Institute) before the start of the MBIR fast neutron reactor operation was carried out. The content of natural (40K, 226Ra, 232Th) and artificial (90Sr, 137Cs) radionuclides in the main components of freshwater ecosystems: surface and underground waters, bottom sediments, floodplain soils and vegetation, and ichthyofauna was estimated. It has been shown that the specific activity of 137Cs in the waste water of industrial storm sewerage (PLK-1) of the enterprise is 10-70, 90Sr 2-10 times higher compared to the surface waters of reservoirs of its zone of influence. This is due to the removal of radionuclides from the site of local contamination in the sanitary protection zone of SSC RIAR. In Cheremshansky Bay, downstream, the concentration of radioisotopes decreases by 8-50 times due to dilution processes and their sorption by bottom sediments and hydrobionts. It is noted that the sorption properties of bottom sediments are determined by the presence of organic compounds in their composition. The multidirectional nature of the accumulation of artificial radionuclides in floodplain soils and plants is shown. In some cases, it is determined by the distance from the source of gas-aerosol emissions of radioisotopes and affects the secondary pollution of freshwater ecosystems. Monitoring data demonstrate a stable decrease in the content of artificial radionuclides in surface waters. In Cheremshansky Bay in 2005-2020 for 137Cs it was 5 times, for 90Sr it was 3 times. It has been noted that in recent years, the specific activity of artificial radionuclides in sewage of SSC RIAR, surface and underground waters, as well as fish in the zone of enterprise influence is at the level of the regional background and is 1-3 orders of magnitude lower than the current radiological standards. The importance of further radioecological monitoring of freshwater ecosystems in the SSC RIAR location area after the commissioning of the MBIR for assessing the impact of the new reactor on humans and the environment is shown.