ОЦІНКА БАР’ЄРНИХ ВЛАСТИВОСТЕЙ ЗОНИ АЕРАЦІЇ НА ДІЛЯНЦІ ПУНКТІВ ЗАХОРОНЕННЯ РАДІОАКТИВНИХ ВІДХОДІВ У ЧОРНОБИЛЬСЬКІЙ ЗОНІ ВІДЧУЖЕННЯ

The paper presents estimates of groundwater recharge rate from precipitation and evaluates the potential of the vadose zone to retard and attenuate radionuclides at the “Buryakivka” radioactive waste disposal facility (RWDF) and the “Vector” industrial complex (IC) within the Chornobyl Exclusion Zone. Understanding the patterns of groundwater recharge, groundwater flow, and radionuclide migration in the vicinity of these facilities is crucial for conducting safety assessments for waste disposal and storage. The study area is situated within the Chystogalivska moraine ridge and is characterized by the presence of an unconfined aquifer in Quaternary deposits, which is mainly recharged by atmospheric precipitation. A combination of methods was applied to assess groundwater recharge rate. Analysis of groundwater level dynamics and chloride-ion balance in groundwater and precipitation yielded consistent groundwater recharge rate estimates in the range of (55–65) ± 15 mm/year. The adequacy of these estimates was confirmed through calibration of the regional groundwater flow model. The obtained recharge estimates were used to evaluate the barrier properties of the vadose zone soils with respect to the migration of Chornobyl-derived radionuclides and radionuclides present in the waste streams of NNEGC “Energoatom”. The calculations were performed using migration models that take into account for advection, dispersion, sorption, and radioactive decay. A screening analysis showed that the main groundwater contamination risks are associated with 90Sr, 3H, and 14C. For these radionuclides, the migration time through the vadose zone and the concentration attenuation factors in groundwater were assessed, taking into account the above-mentioned geo-migration mechanisms included in the model. The calculated parameters can be used in integrated geo-migration models that consider the barrier properties of the geological environment in both near-field and far-field zones of the RWDF, in combination with dose models for determining the waste acceptance criteria for disposal.