Purpose: The purpose of the work is to determine and analyze the main parameters, which characterize the impact of fisheries activities on the conditions for biological amelioration of the cooling pond of the Khmelnytskyi NPP. Methodology. Ichthyological material was selected from commercial catches of gillnets with a mesh size of 36-120 mm in the summer-autumn period of 2021 and the autumn period of 2024. A total of 244 net-days were analyzed, of which 2268 individuals of different species were collected for mass measurements, and 434 individuals for full biological analysis. The collection and analysis of materials were carried out according to generally accepted methods. To assess the theoretical survival of silver and bighead carps, the annual natural mortality rate was used, which was determined based on the natural mortality rate calculated using the parameters of the Bertalanffy equation. The abundance of silver and bighead carp generations for a given year was determined based on the volume of stocking, average natural mortality rates, and commercial catch parameters. The volume of stocking and catch was taken from official reporting data. Calculations were performed in MS Excel 2016. Findings. The majority of the commercial stock of the ichthyofauna of the studied pond in recent years were silver and bighead carps (on average 32.7%), Prussian carp (18.7%), roach (15.1%) and common carp (10.8%), the composition of dominant species was characterized by stability, with the exception of an increase in the share of Prussian carp. The actual stocking rates of the pond generally corresponded to the planned ones, however, the commercial catches amounted to only 12% of the planned ones. The average total mortality for middle age groups, according to the analysis of the catch curve, was φZ=0.42, which allows assessing their estimated annual catch at the level of φF=0.03…0.07. In contrast, for older age groups, the total annual mortality rate was φZ=0.47, while the average estimated annual fishing mortality was φF=0.26…0.27. Meanwhile, calculations of annual natural mortality for older age groups based on the analysis of the catch structure and catch statistics data gave the value φF=0.01…0.05. To localize the negative impact of secondary (due to increased natural mortality) pollution of the pond at an acceptable level, it is necessary to introduce moderate harvest of ichthyomas of middle age groups of biological control agents with an annual fishing mortality coefficient at the level of φF =0.05-0.10, and increased catch of age groups from age-7 and older with φF=0.30…0.40. To ensure maximum effect of biological control, the optimal gears for catching silver and bighead carps are gill nets with a mesh size of a=90-100 mm. Originality. General trends in the dynamics of integral characteristics of the commercial stock of silver and bighead carps were determined in the context of the scientific fundamentals of managing the biomass of biological control agents. The knowledge on the methodological principles of ensuring the effectiveness of biological amelioration of technical water bodies has been deepened. Practical value. The results obtained were used to adjust the procedure for fishery exploitation of the Khmelnitsky NPP pond in order to implement biological amelioration through the directed development of ichthyofauna. Keywords: Cooling pond, ichthyofauna, biological amelioration, Chinese carps.

Calculation of the Temperature State of Fuel Elements in a Cooling Pond of Power Block No. 4 of Beloyarsk Nuclear Power Plant in Beyond-the-Design Accident

The paper is dealt with the study of some peculiarities of phytoplankton and zooplankton community structure in the river - Nuclear Power Station (NPS) cooling pond system. The river flowing into the cooling pond is the main source of its water supply. Plankton structure in this system was considered from the standpoint of the continuum concept of three types: continuum of indistinguishability, gradient, and metameric continuum. It has been shown that in the watercourse, including several lentic elements represented by ponds, plankton structure was discrete-continuous, whereas in the cooling pond it was continuous. The metameric continuum was typical to phytoplankton of lentic sections of river system (ponds and estuaries). The continuity index (Ic) was put forward for the quantitative assessment of the ecological continuum.

In this study, the long-term (i.e., over a 27-year period) dynamics of 137Cs content are presented for seven species of fish in both the cooling pond (CP) of the Chornobyl Nuclear Power Plant and the Kaniv Reservoir (KR). The decline of 137Cs specific activity in fish exhibits various patterns. For certain years in the KR, fish belonging to different ecological groups experienced an increase rather than a decrease in specific activity levels of 137Cs. From 2012 to 2014, the concentration of 137Cs in all studied species in the KR ranged from 4 to 23 Bq/kg. In the CP during 2012–2013, fish still showed high contamination levels, ranging from 770 to 8300 Bq/kg. The ecological half-life (Teco) was determined for all the studied fish species. For most fish species (i.e., P. fluviatilis, B. bjoerkna, A. brama, S. lucioperca, A. aspius), the shortest 137Cs Teco values were obtained in the CP, being a highly radiocaesium-contaminated waterbody. In contrast, two fish species (R. rutilus and S. glanis) in the CP exhibited a considerably slower rate of 137Cs removal from their bodies compared to even the relatively cleaner KR. Moreover, the 137Cs Teco in R. rutilus and S. glanis was nearly twice as long as that observed in other species within the CP. We assume that the redistribution of 137Cs in the body of fish is affected by multidirectional mechanisms: accumulation, retention, and/or excretion. The functioning of these mechanisms can vary among different fish species. The observed level of 137Cs content in a particular fish species at a given time point results from the combined effects of these mechanisms. Fish likely have the ability to absorb and accumulate radiocaesium in their bodies selectively, and this demand appears to be species-specific.

During the accident in April 1986, the Cooling Pond (CP) of the Chornobyl Nuclear Power Plant (ChNPP) was heavily contaminated by fuel particles and radionuclides of cesium-137 (137Cs) and strontium-90 (90Sr). Starting from the end of 2014, a gradual decrease of the CP water level began leading to the transformation of the whole reservoir into eight separate sectors and raising the concern of the fate of 137Cs and 90Sr in the future. In this study, two mathematical models were applied to reproduce radioactive contamination of the CP from 1986 to 2021 and to provide a forecast of 137Cs and 90Sr concentrations in the CP water from 2022 to 2030. The hydrodynamic model THREETOX provided three-dimensional (3D) currents in the CP corresponding to hydrological conditions before and after water level drawdown, and these currents were used in the box model POSEIDON-F for the long-term simulations of the changes in 137Cs and 90Sr concentrations in water, bottom sediments, and biota. Seasonal changes in the distribution coefficient (Kd) describing the partition of 137Cs between water and sediments were considered in the box model, which allowed us to reproduce the observed variations of concentration. Calculated concentrations of 137Cs and 90Sr in water and freshwater fish occupying different trophic levels agreed well with measurements for the entire post-accident period. After the water level drawdown, concentrations of 137Cs in the CP water slightly increased in all eight sectors, while 90Sr concentrations significantly increased in sectors close to ChNPP, which was explained by an additional 90Sr source when comparing the simulation results and measurement data. Using the model forecast from 2022 to 2030, we predict that the concentration of both radionuclides will gradually decrease in new water bodies of the Cooling Pond except in the northern sectors, where the suggested additional source of 90Sr will lead to a stabilization of 90Sr concentrations.

Evaluating changes in radionuclide concentrations and groundwater levels before and after the cooling pond drawdown in the Chornobyl Nuclear Power Plant vicinity

Changes in the absorbed dose rate of external and internal exposure of the representatives of fish fauna of the cooling pond of the Chornobyl NPS and Lake Azbuchyn after the interruption of water supply into the cooling pond at the end of 2014 were investigated in 2014-2021. Changes in hydrological regime resulted in the decrease in water level in the cooling pond by 6.5-7.0 m, whereas in Lake Azbuchyn - by 2.5-3.0 m. In this case, <sup>90</sup>Sr concentration activity in the water and biota increased. It has been found that in 2021 dose load from the incorporated <sup>90</sup>Sr on fish of the cooling pond increased on the average by a factor of 4.5, whereas in Lake Azbuchyn - by a factor of 7.5 as compared to previous period (prior to a decrease in water level). The external dose rate for fish of the cooling pond remained almost unchanged, whereas in Lake Azbuchyn it increased as a result of replacing littoral and sub-littoral zones of the lake with the sections of the bottom characterized by an essentially higher level of radio-nuclide contamination.

Purpose. The work is aimed to determine the real location in space and conduct possible measurement of the true geometric dimensions of the NPP cooling pond dam, especially its underwater part and to detect the additional and previously unaccounted factors that could affect these parameters, as well as the state of the entire structure in general. Methodology. A comprehensive analysis of all available materials about engineering surveys and geotechnical studies was carried out at the dam of the cooling pond of the Zaporizhzhia NPP. Due to this, a more comprehensive look at the results of engineering and geological surveys was obtained. Findings. The state of soils in the body of the earth dam can be influenced by weakened and poorly studied zones of the dam. These zones were determined based on the analysis of the soil studies data of the dam’s ground. Previously uncovered issues on the operation of the facility were raised and considered. The ways and methods for additional study of the earth dam of the cooling pond were selected, the conditions for their use were substantiated. A numerical relationship between the thickness of loose soils and the amount of surface subsidence were determined for the first time. A generalized geological section of the dam body was compiled for further modeling of geotechnical processes. Originality. For the first time since construction, a comprehensive program was developed for assessing the technical condition of the cooling pond dam using innovative methods from the Laboratory of Research of Nuclear and Thermal Power Plants in Prydniprovska State Academy of Civil Engineering and Architecture (PSACEA). In particular, combined hydrographic-geodetic and aerovisual methods were proposed using specially designed universal leading signs that have no analogues in world practice. Practical value. The application of the developed comprehensive program using innovative methods allows assessing the technical condition of the cooling pond dam of the NPP.

Evaluating Changes in Radionuclides Concentrations and Groundwater Levels Before and after the Cooling Pond Drawdown in the Chornobyl Nuclear Power Plant Vicinity

The Tree Cooling Pond Effect and its Influential Factors: A Pilot Study in a Subtropical City, Australia

Dynamics of Periphytic Bacillariophyta at Different Stages of Operation of the Chernobyl Nuclear Power Plant Cooling Pond (Ukraine)

Given the importance of understanding long-term dynamics of radionuclides in the environment in general, and major gaps in the knowledge of 137Cs particulate forms in Chernobyl exclusion zone water bodies, three heavily contaminated water bodies (Lakes Glubokoe, Azbuchin, and Chernobyl NPP Cooling Pond) were studied to reconstruct time changes in particulate concentrations of 137Cs and its apparent distribution coefficient Kd, based on 137Cs depth distributions in bottom sediments. Bottom sediment cores collected from deep-water sites of the above water bodies were sliced into 2 cm layers to obtain 137Cs vertical profile. Assuming negligible sediment mixing and allowing for 137Cs strong binding to sediment, each layer of the core was attributed to a specific year of profile formation. Using this method, temporal trends for particulate 137Cs concentrations in the studied water bodies were derived for the first time and they were generally consistent with the semiempirical diffusional model. Based on the back-calculated particulate 137Cs concentrations, and the available long-term monitoring data for dissolved 137Cs, the dynamics of 137Cs solid–liquid distribution were reconstructed. Importantly, just a single sediment core collected from a lake or pond many years after a nuclear accident seems to be sufficient to retrieve long-term dynamics of contamination.

The study of the transformation of substances in the basin of the Selenga River—the main tributary of Lake Baikal—under anthropogenic pressure and in the context of global climate change, is especially important for the lake, a globally important source of drinking water. The ecosystem of Lake Gusinoe is one of the key objects in the Selenga River basin that is exposed to significant anthropogenic pressure. This study presents the results of an analysis of water level changes and physicochemical parameters of the water mass of Lake Gusinoe; literature data from 1951 to 2017 and own data from 2017 to 2021. The water level in the lake had depended on natural factors before the Gusinoozersk GRES was launched; however, since the plant has begun using the lake as a cooling pond, its level has actually been regulated by the economic entity. Over the years, there has been a significant increase in mineralization, sulfate, sodium, fluoride and organic matter fractions resistant to oxidation. Seasonal increases in iron and manganese concentrations in water were detected. Increased concentrations of nutrients and organic matter fractions resistant to oxidation were registered at the wastewater discharge sites. Heavy metals in the bottom sediments of Lake Gusinoe accumulate mainly in the silt of the deep zone of the lake. Plants growing in the zones of influence of the Gusinoozersk GRES and Gusinoozersk wastewater discharge accumulate the largest amount of metals.

Biodiesel Production using Oil Extracted from Cooling Pond Wastewater by Esterification of Sulfonated Carbon Catalyst and Transesterification of Na<sub>2</sub>CO<sub>3</sub> Catalyst

Biological Characteristics of Bleak Alburnus alburnus (Cyprinidae) from the Cooling Pond in the Pechora River Basin

Colonial Invertebrates in the Zooperiphyton of the Cooling Pond of Combined Heat and Power Plant (Western Siberia)

Plant Cover Transformation in the Shallow Water Habitats of the Cooling Pond of the Chernobyl NPP as a Result of Its Descent

The presence of specific components in the environment can change the state of cenoses. The effect of ionizing radiation on plant communities, animals and humans have been well studied, while the effect on soil microflora has not been insufficiently studied. In this paper investigated the effect of radionuclide contamination on microflora of soil samples from the territory of PTLRW "Red Forest 1" (trench), "Red Forest 2" (outside the trench), " Cooling Pond " and " Zalissia ". Phospholipid fatty acid (PLFA) content was obtained by PLFA analysis. The highest level of total PLFA was observed in the territory of "Zalissia" which was 17.40 ± 10.59 μg / h. From the territory of PTLRW "Red Forest 1" (trench) and "Red Forest 2" (outside the trench) the level of total PLFA was 16.29 ± 3.43 μg / g and 16.40 ± 2.90 μg / h, respectively. The PLFA content of the "Cooling Pond" was significantly different from the "Red Forest" and " Zalissia ". The taxonomic groups assessment of the samples, a fungus, gram-positive and gram-negative bacteria content increased in PTLRW "Red Forest" relative to the point "Zalissia ".

Once-through cooling systems of NPPs and TPPs have well-known advantages compared with reverse systems. Currently in Russia, their design is not allowed according to the Water Code due to environmental concerns. The basis for such a decision for condensing power stations is disputed by the professional community. The question on the abolition of this ban for NPPs and TPPs on the initiative of the Ministry of Energy of the Russian Federation is decided at the legislative level. In a separate class can be distinguished once-through cooling systems with cooling ponds of the marine type. They use the advantages connected with unlimited amount of water for cooling. The associated environment protection problems can and must be solved at the design development stage. The article discusses the issues of substantiation of their layout and parameters at the predesign stage, taking into account the requirements of environmental protection. A coupling physical and numerical modeling is proposed as a tool of computational justification. With such approach, the advantages of both the modeling kinds are used, and it becomes possible to consider the service cooling water system as a system of interconnected components. The article presents an example of hybrid modeling for elaborating measures aimed to prevent silting of the NPP water intake and water conduit structures caused by deposition of suspended drift. Prospects for application of the proposed method for justification of cooling systems as an important element in improving competitiveness and also developing the export potential of Russia’s energy complex are considered.

Моделирование естественной конвекции у поверхности отработанных тепловыделяющих сборок в бассейне выдержки АЭС