Sorption and mobility of radioactive Ni in Wolsong waste repository site, South Korea

Radioactive nickels are significant environmental concerns because of their long half-lives (⁵⁹Ni = 76,000 years and ⁶³Ni = 100.1 years) and high proportions in nuclear wastes in the repositories. Therefore, the investigation of sorption and mobility of Ni at the disposal facility sites is important for the prediction and evaluation of radiological risks to the public. Herein, the batch sorption and column experiments were performed under various geochemical conditions using site-specific rock and groundwater samples collected at the Wolsong low and intermediate level waste (LILW) disposal facility site in South Korea. The batch sorption results revealed that the sorption of Ni was strongly affected by the pH. Approximately 20% Ni adsorbed at pH 5, which enhanced over 90% at pH > 8. The batch sorption results were used to develop the surface complexation model (SCM) to predict the Ni sorption and its mobility behavior. The non-electrostatic generalized composite (GC) SCM approach simulated the Ni sorption data well. We believe, our study can interpret and extrapolate the sorption and transport behavior of Ni in the underground repository conditions.