Modelling of the Fate of 137Cs and 90Sr in the Chornobyl Nuclear Power Plant Cooling Pond before and after the Water Level Drawdown

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