Experimental And Simulated Study Of Radionuclide Migration In Fractured Granite

Radioactive nuclide migration in the fractured granite is an important research aspect in High-level radioactive waste geological disposal.It's has great significance on development of the nuclear waste disposal.In this paper,Single fractured granite device and single fracture with filling device and diffusion device and dispersion device are designed and processed on basis of summarizing the research status at home and abroad.Completed the experiments of the radionuclide mix?U and Th?migration successively.Moreover,simulation and prediction of U-238 and Th-232 and Pu-242 and Am-243 migration in BeiShan fracture system on the basis of the correlation parameter get from indoor experiment.The main conclusions are as follows:?1?The retention of Th by granite superior than U.Radionuclide diffusion of 2mm thick slices is higher than 4mm thick slices.The diffusion coefficient for U and Th in granite slices range from 3.73�10^-11to 1.81 � 10^-117.16�10^-12to 6.89 � 10^-12.The coefficient of retardation for U and Th in granite slices range from 9097 to 8933 form 14565 to 14328.?2?The transport rate and ability of nuclides in granite fracture are related to flow speed.The dispersion coefficient for U and Th in granite slices range from 5.65�10^-10 to 3.87�10^-10 form8.18�10^-11to 1.49 � 10^-12.The coefficient of retardation for U and Th in granite slices range from 8861 to 9100 form 14418 to 14152.?3?In the process of radionuclide transport in single fractured granite,breakthrough curve of tailing phenomenon is more obvious and the relative concentration decreases with flow rate decrease due to the time growth of radionuclide contact with granite fracture surface,and nuclide in granite may somehow potentiate the effect of Coefficient?ion exchange and sedimentation.Th is greater than U in the decrease degree of relative concentration values of radionuclides.The main reason is that Th hardly soluble in water and difficult to migrate.?4?Longitudinal dispersivity of U is higher than Th in single fractured granite.U transport faster than Th.?5?By contrast with breakthrough curve of U,the breakthrough curve of U under radionuclide mix conditions,peak time advanced and relative concentration value increases.The reason may be ion exchange is affected to some extent.Lead to retardant ability of granite drop off.?6?Breakthrough curves of Fissure walls with fillings,the relative concentrations values are from largest to smallest montmorillonite?goschwitzit and chlorite.The peak time are from largest to smallest montmorillonite?goschwitzit and chlorite.The results showed that mineral composition of fracture affects radionuclide migration rate.Fill cracks of montmorillonite with minimum migration rate.longitudinal dispersivity are from small to big chlorite?goschwitzit and montmorillonite.?7?Using the model of one-dimensional multi-channel solute transport,according to the distribution law of BeiShan fracture distribution rule,adopt the correlation parameter get from indoor experiment,predict U-238 and Th-232 migration in BeiShang fissure system.Moreover,use same model for toxic nuclide Pu-242 and Am-243 migration.