Nuclide Transport Numerical Simulation Of High Level Radioactive Waste Geological Disposal

With the development of nuclear science, nuclear technique has been widely used inmany fields, such as national defense,industry,agriculture and medicine. Large amount ofhigh-level radioactive waste (HLW) has been produced,which can make great harm tonatural environment and human society. Attentions have been devoted in recent years tothe challenge of how to safely store nuclear waste. The deep geological disposal isregarded as the most reasonable and effective way to safely dispose HLW in the world，andradioactive nuclide transport in geological barrier is one of key issues which safetyevaluation of high level radioactive waste deep geological disposal.Radionuclide transport of geological barrier is very complicated, mainly displays inwhich is heterogeneity and discontinuity of transfer medium and too much transport time（tens of thousands of years to hundreds of thousands of years）and many uncertainfactors，and so on.In order to resolve solute transport in the fracture media of far field,conceptual and mathematical models of solute transport in single fracture are builtaccording to the double media theory, and analytic solutions with injection of stableconcentration are deduced by Laplace transform. Relative concentrations of Th-229,Cs-135and Se-79in fracture and matrix are simulated respectively based on MATLAB numericalsimulation software the analytic solution, and their transport distance in fracture anddiffusion depth in matrix are researched in detail. The results show that the retardationcoefficient is negatively related with transport distance and diffusion depth of thesenuclides.Moreover, many parameters, such as aperture, hydraulic gradient, will influenceon these nuclide transport in fractured media, these influence are analyzed, and the resultsindicate that transport distance and relative concentration of these nuclides will increase ofaperture or hydraulic gradient. At the same time, according to the the transmissivity hascharacteristics of the normal distribution in fracture network system, the fracture media isdescribed by one dimensional multi-way solute model, and the transport ofabove-mentioned nuclides in fractured media is simulated with this model.