Numerical Simulation of ²³⁹Pu(Ⅳ) Transport in Granite Fissure

According to the dual continuous medium model, the nuclide transport equations of fissure and matrix are derived in parallel plate single fractured granite based on the nuclide migration rule in this paper, the relative concentrations of nuclide are obtained in fissure and matrix. The ²³⁹Pu(Ⅳ) is selected as the simulation subject, the distributions of relative concentration are analyzed in granite fissure and matrix of the study region, combined with the permeability coefficient, the partition coefficient and other parameters of the study region, and the developing trend and migration of ²³⁹Pu(Ⅳ) are predicted in fissure and matrix. The simulation shows that this diffusion velocity of ²³⁹Pu(Ⅳ) is very slow, the range of diffusion is only millimeter level after 0.5×10⁵ a in matrix, but it is 3 m in fissure. The result shows that this area of the granite meets the condition of radioactive waste disposal containing ²³⁹Pu(Ⅳ) etc. At the same time, the rule of the nuclides migration is discussed due to the variation of some parameters in the fissure, including the average speed of fissure water, gap width, permeability coefficient, radionuclide half-life, retardation factor in matrix and fissure etc.