A hydrogeochemical site descriptive model (SDM) is essential for evaluating the long-term safety of deep geological repositories for high-level radioactive waste (HLW). This review analyzes the hydrogeochemical SDM methodology developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) for the Forsmark repository site. The SDM framework integrates quantitative field-based models with process-oriented conceptual models, evolving iteratively from feasibility study through initial and complete site investigation stages. The hydrogeochemical workflow comprises data acquisition and quality management, explorative analysis identifying groundwater types and end-member compositions (Deep Saline, Glacial, Littorina Sea, and Altered Meteoric Waters), quantitative modeling through M3 mixing calculations and PHREEQC geochemical simulations, and interdisciplinary integration with hydrogeological and transport models. The Forsmark SDM successfully characterized the stratified groundwater system, confirmed the long-term stability of reducing and pH-buffering conditions at repository depth, and quantified the role of paleohydrogeological events in shaping present-day hydrochemistry. Based on these findings, methodological considerations for developing a hydrogeochemical SDM in Korea are suggested, including updated thermodynamic database, open-source reactive transport codes, site-specific end-member definition, and global sensitivity analysis for uncertainty quantification.

Keywords: Site descriptive model (SDM), Hydrogeochemistry, Deep geological disposal, Forsmark, Groundwater mixing