Abstract: This paper describes the visual modflow that was used to build a three dimensional groundwater flow field for simulating the waste tank with ³H leakage at a NPP site in case of an accident. The results show that the migration of ³H in geological condition is slowerand it need 8 years for its peak of concentration to get into river. The migration of ³H is dominant in horizontal direction and minor in vertical direction.

Key words: Nuclide migration, Groundwater, Numerical Simulation, Modflow