Performance of clay based buffer material developed for use in a nuclear fuel waste disposal vault

This study is designed to evaluate water diffusion parameters of clay based buffer material (mixture of clay and sand) used in nuclear fuel waste disposal vault for the following three cases: (a) No volume change in the soil fabric with no air loss. (b) No volume change in the soil fabric with air loss. (c) A complete change in the soil fabric with air loss.One dimensional diffusion type unsaturated flow equation was solved by finite difference method. Powell's optimization technique was used to minimize the material parameters in the proposed diffusion function. The adopted technique makes the use of both theory and experimental data. In this concern several tests have been performed for the three aforementioned conditions to measure the volumetric water content and the soil water potential distributions as a function of time and space.The calculated diffusion parameters were used to predict the volumetric water content and the soil water potential as a function of space and time for longer period of time