Abstract: In order to describe in detail the characteristics of water flow in a long time series after the closure of radioactive waste disposal facilities and to optimize the design of disposal vault. The simulation of the closed radioactive waste disposal facilities is carried out by Porflow. The results show that with the gradual degradation of the cover system and disposal components, there are local water flow rising areas at the bottom and both sides of the disposal vault in the 150-170 years after the closure of the disposal facilities. In the years of 0-150, the cover system infiltration water flows away from both sides of the disposal vault, and the maximum velocity is 0.41 cm/a; After the 150th year, the disposal vault area gradually became the dominant channel, and the maximum velocity was 86.4cm/a. The high velocity mainly occurred in the top corner of the disposal vault and the groundwater collecting pipe gallery area; The overall saturation changes little, the saturation in the disposal vault area remains at 0.99, the saturation on both sides and at the bottom of the disposal unit shows an upward trend, and the dynamic variation range is 0.3-0.5. The degradation of disposal components will not have a significant impact on the disposal facilities in a long time scale, and the catchment pipe gallery is a potentially advantageous channel for nuclide migration.

Key words: near-surface waste disposal facility, water flow characteristics, unsaturated zone, Porflow, pressure head, flow velocity, saturability