Using the coupled thermo-hydro-mechanical model for saturated-unsaturated porous media developed by the author and taking one set of real physical and mechanical parameters of buffer material

rockmass and canister (replaced by heater) as the basic computation condition

this paper conducts 2D FEM analyses for a hypothetical nuclear waste repository

in which high

middle and low permeability values were applied. Though investigating the change of magnitudes and directions of the flow velocities in the near field

it is realized that: under the condition that the other computation parameters are the same

the higher the permeability of the buffer

the faster the flow

and the time for the buffer to enter a saturated state is also shorter; after the buffer reaches the saturation state if the vitrified waste releases heat continuously

the action of the temperature gradient in the near field may exceed the action of the hydraulic gradient

so that the direction of the flow velocity reverses and the water transports from the inside to the outside; the flow velocity fields have an obvious difference according to different permeability values so that the diffusion of radioactive nuclide with underground water flow is also complex and changeable.