NUCLIDE TRANSPORT MODEL IN FRACTURED ROCKMASSES AND ITS APPLICATION TO SAFETY ASSESSMENT OF GEOLOGICAL REPOSITORY
裂隙岩体核素迁移模型及其在高放废物地质处置库安全性能评价中的应用

Based on random fracture parameters,a multiple-path transport model for nuclide transport in fractured rockmasses of relatively low permeability is proposed using fracture linear superposition of one-dimensional transport model. The average nuclide migration rate(Bq/a) at a given fixed point in space is determined with this model. The transmissivities of fracture are assumed to be a random distribution,and the random distribution of fracture transmissivity is evenly divided into finite segments,each of which represents a pathway with relevant fractue parameters,e.g. transmissivity,aperture,and probability. The obtained results are weighted by the transmissivity distribution probability of the relevant pathway. It has been demonstrated by means of case study that the nuclide diffusion into matrix from fracture has a great effect on the nuclide release rate from host rockmasses. This process can be considered to be effectively retarding nuclides. The results of multiple pathway transport model also show that the nuclide migration process is evidently dominated by these pathways with relatively high transmissivity.