3:30 PM - 3:45 PM
[3C12] Measurements of Thermodynamic Data of Water in Na-Bentonite in the Pressure Release System and Saturated Condition by Relative Humidity Method
Keywords:Geological disposal, Buffer material, Bentonite, Montmorillonite, Relative humidity, Activity of water, Gibbs free energy, Thermodynamics, Swelling stress
Buffer material composing engineered barrier in the geological disposal of a high-level radioactive waste develops swelling stress by penetration of groundwater from the surrounding rock mass. In earlier studies, we measured the activity of water and the Gibbs free energy of water in bentonite by vapor pressure method, and proposed a model to analyze swelling stress based on thermodynamic theory. On the other hand, data for the vapor pressure of water in bentonite are limited. In this study, we determined vapor pressure by measuring relative humidity and temperature for water in bentonite and montmorillonite which is the major component of bentonite, and calculated the activity of water and the Gibbs free energy. Additionally, we analyzed swelling stress based on the thermodynamic model and discussed by comparing to data reported so far.