Risk assessment of radionuclide contamination spreading while flooding coal mined-out rocks

Ivan Sadovenko¹, Oleg Ulytsky², Аlina Zahrytsenko¹, Kateryna Boiko²

¹Dnіpro Unіversіty of Technology, Dnipro, 49005, Ukraine

²State Ecological Academy of Postgraduate Education and Management, Kyiv, 03035, Ukraine

Min. miner. depos. 2020, 14(4):130-136

https://doi.org/10.33271/mining14.04.130

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ABSTRACT

Purpose. To investigate pathways and concentrations of the most dangerous radionuclides entering the surface and groundwater in terms of hydrodynamic situation re-establishment in the zone of radiation-hazardous mine field objects in the southern wing of the Central Donbas coal industrial region for environmental assessment.

Methods. Hydrodynamics and migration parameters characterizing the stage of mine workings’ flooding – have been investigated. This phase is marked by the establishment of steady-state hydrodynamic regime with laminar groundwater filtration and radionuclide migration from the source of pollution to the river drainage. The parameters have been estimated on the basis of numerical modelling of geofiltration using available data from similar research and experimental studies. The resulting model has been calibrated by assessing the components of the water balance within the drainage area of the territory under research. Radionuclide migration pathways are defined by mathematical tools for mass-transfer calculation (MODPATH) using input parameters of the geofiltration model. To determine the concentration value of radionuclides entering the river drainage through the groundwater discharge, analytic calculations have been carried out. Facts and previous assumptions from different sources have been subjected to analytical comparison in order to outline the measures for control and technical settlement of possible threats and their ongoing assessment.

Findings. Predictive modelling of the initial phase of hydrodynamic regime stabilization during mine working flooding has been performed. Possible concentrations of Sr90 that are expected to enter the river drainage at the stage of groundwater level recovery to absolute marks (+120…+145 m) are calculated. It is found that the probability of Сs¹³⁷ ions migration is very low, which can be explained by the specifics of migration mechanism. It has been demonstrated that radionuclide migration pathways differ in the form of distribution and groundwater flow directions at the final stage of mine flooding. It has been established that the developed continuously operating hydrochemical model of the region together with the application of actual monitoring data obtained from the underground and surface hydrosphere within the government-controlled area could be considered a practical tool of possible environmental threats control.

Originality.The research novelty is associated with the investigation of quantitative parameters of radionuclide migration within the abandoned coal mining areas on the basis of geofiltration modelling of current mine flooding conditions, when groundwater level reaches the critical mark, and the level stabilization process is accompanied by water resources recovery and water balance components transformation.

Practical implications. The proposed research technique enables to forecast environmental consequences of coal mines’ flooding in Ukraine and to assess the hydrosphere pollution not only with radionuclides but also with other chemical elements; it also creates tools for control and management of negative environmental situations.

Keywords: coal, mine, flooding, geofiltration modelling, radioactive contamination

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