Prediction Model for Saturated Hydraulic Conductivity of Bentonite Buffer Materials for an Engineered-Barrier System in a High-Level Radioactive Waste Repository

In the design of HLW repositories, it is important to confirm the performance and safety of buffer materials at high temperatures. Most existing models for predicting hydraulic conductivity of bentonite buffer materials have been derived using the results of tests conducted below 100 degrees C. However, they cannot be applied to temperatures above 100 degrees C. This study suggests a prediction model for the hydraulic conductivity of bentonite buffer materials, valid at temperatures between 100 degrees C and 125 degrees C, based on different test results and values reported in literature. Among several factors, dry density and temperature were the most relevant to hydraulic conductivity and were used as important independent variables for the prediction model. The effect of temperature, which positively correlates with hydraulic conductivity, was greater than that of dry density, which negatively correlates with hydraulic conductivity. Finally, to enhance the prediction accuracy, a new parameter reflecting the effect of dry density and temperature was proposed and included in the final prediction model. Compared to the existing model, the predicted result of the final suggested model was closer to the measured values.