Presentation Information
[2B03]Analytical Evaluation of the Effect of Sulfate Leaching from Waste Forms on Bentonite Permeability and Consideration of the Mechanism
*Tatsuo Saito1 (1. JAEA Radioactive Wastes Disposal Center)
Keywords:
Sulfate,Concrete,Bentonite,Permeability coefficient,Geochemical calculation code,Disposal of radioactive waste
In the disposal of radioactive waste, it is important to evaluate the impact of sulfates in the waste on safety performance. Specifically, regarding the permeability of the bentonite layer, which contributes to the water-stopping performance of disposal facilities, it is necessary to assess the effects of dissolution of bentonite constituent minerals caused by sulfate minerals, as well as ion exchange associated with high ion strength in pore water. This study analytically evaluated the response of bentonite permeability coefficient to sodium sulfate content in waste using a geochemical calculation code. The mechanism for permeability increase was examined through comparative analysis with existing experimental studies. The calculations showed an exponential increase (R2=0.92) in the permeability coefficient of the bentonite layer with respect to sulfate content. Regarding the factors involved, it was considered that when the sulfate content exceeds a certain value, a reaction may form where the permeability coefficient increases in stages due to Na+ supply from the concrete layer and the promotion of montmorillonite dissolution.