A PERMANENT MATHEMATICAL MODEL OF FILTRATION AND MIGRATION CONDITIONS BETWEEN THE PRIPYAT AND UZH RIVERS OF THE CHORNOBYL EXCLUSION ZONE
Authors:   Institute for Safety Problems of Nuclear Power Plants of NAS of Ukraine, Chornobyl, Ukraine, PANASIUK Mykola , SOSONNA Natalia ,   Institute for Safety Problems of Nuclear Power Plants of NAS of Ukraine, Chornobyl, Ukraine, KOVALENKO Ihor ,   Institute for Safety Problems of Nuclear Power Plants of NAS of Ukraine, Chornobyl, Ukraine, BUZYNNYI Mykhailo ,   SI "O.M. Marzieiev Institute for Public Health", NAMSU, Kyiv, Ukraine, SHEVCHENKO Oleksii ,   Ukrainian Hydrometeorological Institute (UHMI), Kyiv, Ukraine
Published: May 2024

Background. Over the past 8–10 years, the radio-hydroecological and hydrogeological conditions of the Chornobyl Exclusion Zone have changed significantly. Under the influence of the decommissioning of the water-containing cooler, the levels, speed and direction of movement of groundwater have changed on a regional scale. New radiation-hazardous objects were created: Storage of spent nuclear fuel (SSNF-2) and Centralized storage of spent nuclear fuel (CSSNF). The impact of climate change on the regime of water bodies has also increased. To study the impact of radiation-hazardous objects on the water environment of the exclusion zone, to forecast changes in hydrogeological conditions under the influence of climate change and man-made loads, it is necessary to create an updated model of filtration and migration conditions with the possibility of its further adjustment and improvement. Methods. In creating and developing a constant mathematical model based on the finite difference method, the geological and hydrogeological conditions of the research area were considered. Spatial constructions were also carried out to visualize the geological structure using GIS technologies. The filtering scheme was drawn up for computational operations. The QGis program was used to construct the surfaces of geological horizons, and the Visual MODFLOW program was used to develop the filtration model. Results. A model of filtration and migration conditions of the Pripyat-Uzh interfluve of the Chornobyl Exclusion Zone was constructed. The distribution of groundwater levels and heads in the Buchach aquifer was obtained. Forecasts of the paths, directions and time limits of the spread of pollutants with underground water from radiation-hazardous objects have been made. We carried out forecasts of the impact of changes in the boundary conditions of the aquifer on the hydrodynamic parameters of groundwater to justify project decisions on improving the network of observation wells and determining the conditions of flooding of the Chornobyl nuclear power plant site. Forecasts of the impact of global warming on the underground water regime have been carried out. Conclusions. The forecast field of pressure distribution demonstrates the possibility of improving the radiological state of groundwater as a result of: increasing the thickness of the aeration zone and its sorption capacity and accelerating self-purification due to the growth of underground flow gradients. It is important that the unloading of polluted groundwater will not take place in the Pripyat River, but in the isolated residual lakes of the former cooling pond. It will take about 20 years for groundwater to reach the lakes from the Chornobyl nuclear power plant site.