Aleksieieva A. Ecological-radiation Safety of Freshwater Reservoirs under the Influence of NPP Discharges

Scientific and practical results of researches of freshwater reservoirs radionuclide pollu-tion by NPP discharges are given. The thesis presents a solution to the relevant scientific and practical task of developing the standards of ecological safety of admissible levels of radionu-clide pollution of freshwater reservoirs, which are hydrologically connected with technological NPP reservoirs and are used for maintenance of irrigation needs of the population. Based on the analysis of the radioecological studies results in the area of the Yuzhnoukrainskа NPP, we de-termined the reason of the radionuclide composition of the adjacent freshwater reservoirs by the influence of liquid discharges of the NPP, primarily 3H and 137Cs. We also established the de-pendence of the 3H content in freshwater reservoirs on its content in the technological reservoirs of the Yuzhnoukrainskа NPP, and substantiated the necessity of enhanced hydro-ecological monitoring of the 3H content in fresh water reservoirs in the area of the Yuzhnoukrainskа NPP. Ecologically permissible emission levels of all radionuclides present in NPP discharges allowed to supplement the relevant methodology. According to the ecological principle of safety we cal-culated the permissible concentrations of radionuclides (134Cs,137Cs, 89Sr, 90Sr, 106Ru, 54Mn, 58Co, 60Co, 110mAg) in freshwater reservoirs. To determine the conversion rate of 137Cs from irri-gation water to crops we carried out field studies, the results of which were used to improve the method of calculating the permissible concentrations of radionuclides in irrigation water ac-cording to the radiation-hygienic principle. We suggest using the calculated values of permissi-ble concentrations of radionuclides in the system of standards of ecological safety of freshwater reservoirs in the area of NPPs used for irrigation needs of the population. The thesis substanti-ates a comprehensive approach to ensuring the environmental safety of reservoirs, which are hydrologically connected to the technological reservoirs of NPPs, taking into account the radia-tion-hygienic (effective dose of human exposure) and environmental (radionuclide content in bottom sediments) restrictions. Application of this approach will allow carrying out operative assessment of a radioecological condition of reservoirs which are under the influence of NPP discharges. This is the first scientifically grounded comprehensive approach to ensuring the en-vironmental safety of reservoirs, which are hydrologically connected to the technological reser-voirs of NPPs, taking into account radiation and hygiene (effective dose of human exposure) and environmental (radionuclide content in bottom sediments) restrictions. Application of this approach will allow to carry out operative assessment of a radioecological condition of reser-voirs which are under the influence of NPP discharges. We developed the scientific ideas on the rapid assessment of radionuclide contamination of freshwater reservoirs using methods for de-termining the basic radionuclide, basic radiation characteristics and dose price. We determined the indicator «the dose price of irrigation», which can quickly determine the effective human dose received when consuming irrigated crops. The developed method of operative assessment of radionuclide contamination of freshwater reservoir in the NPP area according to radiation-hygienic and ecological safety principles allows to promptly obtain complete information on the level of freshwater reservoir safety in the NPP area: 1) not to exceed the allocated quota 10 μSv/year); 2) not to exceed the limit of radionuclide activity in the biotic components of the reservoir (370 кBq/kg).