On account of the numerous discontinuities and multiple physics involved, the numerical evaluation of pollution propagation is computationally sophisticated and time-consuming. This paper proposes a new approach based on the unified pipe-network method to simulate nuclide migration in highly fractured rock masses. This method explicitly represents fracture networks with interconnected nodes and pipes in a spatial domain and applies a set of universal constitutive models to both fractures and rock matrices. Whether fractures or rock matrix are the dominators of mass transport depends on the connectivity of fracture networks. Minor changes in connectivity may trigger significant percolation threshold effects.