Numerical analysis studies on colloid-facilitated radionuclide migration in a fractured rock

Kuno, Yoshio; Sasamoto, Hiroshi   

To evaluate colloidal effects on radionuclide (RN) migration through a fractured rock, sensitivity analyses were conducted by considering the properties of groundwater colloids. Distribution coefficient for the mobile colloids Kd (m/kg) and colloid concentration M (kg/m) are important parameters since the product of them (Kd M) indicates the colloidal effects on RN migration, which is noticeably enhanced in the case of Kd M 1. Furthermore, colloid migration was simulated by taking into account colloid filtration by the fracture surfaces. Filtered colloids tend to increase with increasing the filter coefficient (1/m). Breakthrough of RNs shows a peak curve since RNs sorbed on the filtered colloids increase and mobile RNs decrease with time. RN distribution to the filtered colloids could have a sufficient impact on RN migration by reducing mobile concentration in the fracture.