Study of Mobility for Radionuclides in Nuclear Facility Sites

Seeun Chang, JongKul Park, Wooyong Um

Econ. Environ. Geol., 2018, 51(2), 99-111

http://dx.doi.org/10.9719/EEG.2018.51.2.99

Abstract

In this study three target radionuclides (60Co, 137Cs, and 125Sb) were reacted with solid samples collected from the nuclear facility sites to investigate their sorption and mobility behaviors for preparing unexpected nuclear accidents. The highest sorption distribution coefficients (Kds) of target radionuclides (60Co=947 mL/g, 137Cs=2105 mL/g, 125Sb=81.3 mL/g) were found in topsoil layer under groundwater condition, and the Kd values of three radionuclides decreased in the order of fractured rock and bedrock samples under the same groundwater condition. High Kd values of 60Co in topsoil layer and fracture rock resulted from the clay minerals present, and the Kd values decreased 58–69 % under seawater condition due to high ionic strength. 137Cs sorption was controlled by the ion exchange reaction with K+ on flayed edge sites (FES) of mica. The 137Cs sorption was the most affected by seawater (89–97 % decrease), while 125Sb sorption was not much affected by seawater. As the results of column and batch experiments, the retardation factors (R) of 137Cs, 60Co, and 125Sb were determined about 5400-7400, 2000-2500, and 250-415, respectively, indicating no significant transport for these radionuclides even in fractured zone with groundwater. These results suggest that even in the case of severe nuclear accident at the nuclear facilities the mobility of released radionuclides (60Co, 137Cs, and 125Sb) can be significantly retarded by the topsoil layer and fractured rock. In addition, the results of this study will be used for the safety and environmental performance assessment of nuclear facilities.