Up to now the influences of temperature field and stress field on the migration of radioactive nuclide with groundwater have been studied rarely. Against this problem

the elasto-plastic model and the relative 2D FEM code have been extended and improved for analysis of coupled thermo-hydro-mechanical processes in saturated-unsaturated porous media developed by introducing percolation and migration equation

so that the code can be used for solving the temperature field

flow field

stress field and nuclide concentration field at the same time. Then a computation example of an assumed nuclear waste repository

in which different values of permeability

distribution coefficient and molecular diffusion coefficient of buffer material are used respectively

the distributions and changes of nuclide concentration in the near field are investigated under the condition of coupled thermo-hydro-mechanical-migratory. The results show that the transport of nuclides in buffer are not influenced by the flow field nearly when the permeability of buffer is low to a certain extent; the less the distribution coefficient and the greater the molecular diffusion coefficient are

the faster the nuclide transport is.