ReO4-和Cs+在北山花岗岩中的迁移特性OA

Deep geological disposal is a widely recognized method for the disposal of high-level radioactive waste both domestically and internationally.The acquisition of migration parameters for key nuclides in the host rock medium of disposal repositories is a crucial component of safety assessments for deep geological disposal.Traditional experimental methods suffer from drawbacks such as lengthy testing periods and the need to crush rock samples.The electro-migration method employed in this study enables ions to rapidly migrate toward the opposite direction of the electrodes under the influence of an electric field,allowing for the rapid acquisition of breakthrough curves for ions in intact granite,thereby effectively addressing the shortcomings of traditional experimental methods.In the model processing,this study employs first-order kinetic adsorption advection-dispersion modeling.While considering the effects of electro migration,electro osmosis,and diffusion-three important mechanisms-the model also incorporates the influence of dynamic adsorption,resulting in more accurate experimental results.This study focuses on granite from the Beishan Xinchang region,using an improved electro-migration device to investigate the diffusion and adsorption characteristics of Cs+and ReO4 in Beishan granite.During the experiments,the i-t mode of the electrochemical work station was utilized to precisely control the voltage applied to the rock samples(±0.001 V)and continuously recorded the current flowing through the apparatus.The electrolyte solutions in the anode and cathode chambers were pumped to an external container via a peristaltic pump for mixing,then added dropwise to the cathode and anode chambers,respectively,to prevent short circuits and overflow in the device.A small amount of sodium bicarbonate was added to the background solution to provide HCO3-and CO32-ion buffers,maintaining the stability of the pH gradient in the background solution and adjusting its pH to weakly alkaline(pH=7.8)to simulate the actual groundwater environment of Beishan.The electro-migration method was used to obtain the penetration curves of Cs+and ReO4-in Beishan granite under different voltage conditions.First-order kinetic adsorption advection-dispersion modeling was employed to more accurately interpret the experimental data.Using the new model,the effective diffusion coefficients Dme of ReO4-and Cs+in Beishan granite under the absence of an electric field are estimated to be(4.68±0.15)×10-13 m2/s and(4.85±0.94)×10-14 m2/s,which are consistent with previously reported results.The adsorption distribution coefficients(Kd)are(9.92±0.07)×10-7 m3/kg and(5.52±0.20)×10-5 m3/kg,respectively,indicating that rhenium is barely adsorbed on Beishan granite.