Development of thermal-hydraulic coupling model for deep-geological disposal of high-level radioactive wastes

Abstract

The buffer plays an important role in a engineered barrier system for the deep geological repository of high-level radioactive waste (HLW). High temperature may result in degradation of buffer performance. It is crucial to investigate the buffer temperature behavior so that its peak temperature is not higher than the criterion of 100 °C. In the present work, the thermal-hydraulic (T-H) coupling model is developed to simulate the histories of temperature and saturation in the disposal repository. This model is validated with the previous simulation works in the DECOVALEX 2015 Task B2 in order to simulate the geological repository of HLW with confidence. The whole repository of HLW in the present works can be reasonably simplified as a single hole with the symmetric boundary conditions on its peripheral sides. Effects of tunnel spacing and hole spacing of repository on the histories of buffer peak temperature are considered since the layout with various spacing is strongly related to the peak temperature of buffer. Based on the comparison of simulation results from the T-H coupling model and T-only model for the different layout of whole HLW repository, the maximum value of peak temperature in the buffer predicted by the T-H coupling model is lower than that from the T-only model. In other words, less area is needed for the selection of repository, rendering that the present T-H coupling model can assist in the design of HLW repository.