Study On Migration Characteristics Of Weakly Adsorbed Nuclide By Column Method

With the rapid development of nuclear energy,the disposal of high-level radioactive waste(high-level waste)is imminent.The most effective disposal method currently considered to be deep geological disposal.Gansu Beishan in China has become an important pre-selected area for the repository.The surrounding rock is mainly granite.The backfill material to be used is bentonite,and the bentonite contains a certain amount of illite.In this work,the sorption and migration behavior of iodine on Beishan granite and illite was studied by pulse column method.The effects of flow rate,particle size,pH,chemical form of iodine,porosity,initial concentration and column length on the sorption and migration behavior were investigated.The experimental results show that:(1)flow rate has a significant effect on the migration behavior of iodide ion on Beishan granite and illite.The diffusion coefficient increases with the increase of flow velocity,and it is linearly fitted,and the fitting effect is good(R2>0.99).The resulting slope dispersion is within the range of previously reported literature.(2)The particle size has a significant effect on the migration behavior of iodide ions on the Beishan granite and illite.With the decrease of the particle size,the partition coefficient Kd gradually increases,mainly due to the decrease of the particle size,and the specific surface area increases.More sorption sites have been added,resulting in enhanced sorption capacity.(3)The sorption of iodide ion on Beishan granite and illite is slightly different.For Beishan granite,the diffusion coefficient decreases gradually with the increase of pH,while for illite,when pH=3?7,with The diffusion coefficient increases with the increase of pH,and the diffusion coefficient is the largest when pH=7,while the diffusion coefficient decreases with the increase of pH when pH=8?12.(4)Beishan granite has slightly different iodide ion and iodate ion,and the sorption capacity of iodate ion(Kd0.30 g/cm3)is stronger than that of iodide ion(Kd=0.17 g/cm3).(5)The effect of porosity on the migration behavior of iodide ion on Beishan granite is not obvious,and further experiments are needed.(6)The column length also has a certain influence on the iodium ion on the Beishan granite.As the column length increases,the sorption capacity decreases.(7)The initial concentration has no effect on the sorption and migration of iodide ions on Beishan granite and illite,because the amount of iodide ions injected is only 20?L,and the amount is too small.However,by varying the different injection concentrations,it was found that the concentration of iodide suitable for the column experiment was 10-4?10-3 mol/L.(8)The sorption capacity of PCR solid polymer for iodide ion is slightly stronger than that of Beishan granite and illite.The research results obtained in this experiment can improve people's cognition level of the migration behavior of radionuclide in geological medium,and provide basic parameters and technical support for the safety evaluation of high-level waste disposal repository in China.