Analysis of double-layered buffer in high-level waste repository

Abstract Buffer is the main component of the engineering barrier system (EBS) in high-level radioactive waste (HLW) disposal repository. Reliable EBS performance assessment requires the delicate numerical modeling of the buffer layer. This study presents the sensitivity analysis of thermal and hydraulic parameters in the repository by using COMSOL Multiphysics, and proposes a new buffer barrier with double layers consisting of buffer-A with higher heat conductivity closing to the HLW canister and buffer-B with lower hydraulic conductivity closing to surrounding rock. From results of the sensitivity analysis, it is concluded that the thermal conductivity and hydraulic conductivity are high sensitivity parameters, and specific heat capacity, water density and water compressibility are low sensitivity parameters. The increase of the thermal conductivity in buffer-A results in effectively reducing the peak temperature in the buffer. Therefore, the double-layer buffer is advantageous and effective for improving the repository safety.