Abstract: The buffer material is critical to long-term safety for geological repository of high level radioactive waste disposal. Based on safety analysis of long-term evolution scenario for repository, this paper focuses on sensitivity analysis of buffer material parameters such as the buffer thickness, the density of buffer material, and the distribution coefficient of radionuclide in buffer material through the Monte Carlo stochastic simulation method. The simulated results indicate that the near field radionuclide release rate is sensitive to the buffer thickness within 1000 years after closure of a disposal repository, and less sensitive thereafter. The near field radionuclide release rate is not sensitive to the density of buffer material. When the distribution coefficient of radionuclide in buffer material increases continuously, the corresponding sensitivity increases gradually. The results show that the sensitivity analysis can provide feedback guidance for the design of buffer material.

Key words: high level radioactive waste, geological disposal, buffer material, scenario, sensitivity analysis