A Review of Geochemical Modeling for the Performance Assessment of Radioactive Waste Disposal in a Subsurface System

Radionuclides are inorganic substances, and the solubility of substances is a major factor affecting disposal radioactive waste release concentrations radionuclides. The degree determines whether nuclide source migrates to far field site. Therefore, most effective method for retarding radionuclide migration reduce in aqueous geochemical environment subsurface systems. In order assess performance facilities, thermodynamic data regarding nuclides water–rock systems minerals environments required; results obtained from analysis these can provide strong scientific basis maintaining safety support nuclear management. pH, Eh time ranges sites cannot be controlled, contrast those under experimental conditions laboratories. Using hypothetical error mechanism assessment may engender incorrect results. Studies have focused on reactions disposal, offered evidence suggesting that mainly affected by environment. However, studies not examined thermodynamics chemical or interactions between water minerals, such as surface complexation adsorption various nuclide-ion species. Simple coefficient models usually been applied obtain empirical formulas deriving Kd describe distributions solid liquid phase Accordingly, this study reviewed previous research applications models, including development sources databases (TDBs) their programs, determination adequacy TDBs case studies, selection application activity equations models. addition, conducted comparisons coefficients derived different Three equations, namely Davies, modified Debye–Hückel, Pitzer four PHREEQC, MINEQL+, MINTEQA2, EQ3/6, were used study. demonstrated when solution’s ionic strength was <0.5 m, differences Davies Debye–Hückel <5%. difference terms calculated <8%. effect temperature slightly influenced modeling outputs equations. future, probability distribution uncertainty parameters equilibrium constant reactive transport simulate long-term sites. findings conducting assessments repositories developing environmental management remediation schemes control marred near-surface contamination.