Evaluation of water quality influence on water discharge of nuclear power plant (non-radiation impact factor)

The main function of the nuclear power plant (NPP) cooling circuit system (CCS) is to remove heat from the power plant equipment. The purpose of this study is to analyze the quality of the make-up, cooling, and return water of the NPP CCS and the surface water of the water body into which the plant discharges water. This study was conducted for the Rivne NPP CCS and the Styr River (Ukraine). Physical and chemical parameters of the water such as temperature, total dissolved solids, total alkalinity, total hardness, Cl^-, SO₄^2-, TSS, dissolved oxygen, chemical oxygen demand, biological oxygen demand over 5 days, NO₃^-, Na⁺, K⁺, ammonia nitrogen, NO₂^-, and PO₄^3- were measured weekly and evaluated during 2019–2022. Consequently, each component was analyzed separately to determine the possible impact of the concentration on the maintenance of the water chemistry regime and water discharge. Meanwhile, selected water quality parameters were correlated using Pearson's correlation coefficient to relate the impact of the recharge water to the water parameter in the system, and the water parameter was related to the component content in the water body. Regarding the assessment of compliance with the operational standards and according to the maximum permissible concentration (MPC), discharges of polluting chemicals were investigated according to the maximum permissible discharge (MPD). Discharges of pollutants from the Rivne NPP do not cause the MPC to be exceeded in the Styr River. The estimated discharges of pollutants, their distribution by components, and the actual water discharge of pollutant components of the Rivne NPP do not exceed 50% of the MPD. Overall, this study indicates that there is no negative non-radiological impact of water discharge of polluting chemicals with the effluent of the Rivne NPP CCS on the surface waters of the Styr River.