• Journal of Soil and Groundwater Environment
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• v.11 no.3
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• pp.12-19
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• 2006

In this study, the stability of Ca-bentonite colloids from Gyeongju area was studied by investigating the changes in the size of the bentonite colloids using a dynamic light scattering method depending on the geochemical conditions such as pH and ionic strength. Kinetic and equilibrium coagulation behavior of the bentonite colloids was investigated by changing the pH and ionic strength of the bentonite suspensions. The results showed that the stability of the bentonite colloids strongly depended upon contact time, pH, and ionic strength. It was also shown that the bentonite colloids were unstable at higher ionic strength greater than 0.01 M $NaClO_4$ at whole pH values considered. In addition, the stability ratio Wand the critical coagulation concentration (CCC) were also calculated using the data from the kinetic coagulation experiments. The stability ratio W was decreased as the ionic strength increased and varied with pH depending on the ionic strength. The CCC of the Ca-bentonite colloids was about 0.05 M $NaClO_4$ around pH 7.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.4
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• pp.341-348
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• 2005

Bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste because of its low permeability, high sorption capacity, self sealing characteristics, and durability in nature. In this study, the potential for separation of bentonite particles caused by the groundwater erosion was studied experimentally for a Korean Ca-bentonite under the relevant repository conditions. Results showed that bentonite particles can be generated at the bentonite/granite interface and mobilized by the water flow although the intrusion of bentonite into fracture by swelling pressure was observed to be small. Different processes of mobilization of theses colloids from the compacted bentonite block have been identified in this study. The concentration of particles eluted in water was increased as the flow rate increased. Thus the result reveals that the erosion of the bentonite surface due to the groundwater flow together with intrusion processes is the main mechanism that can mobilize bentonite colloids in the fracture of the granite.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.177-178
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• 2005