125I在压实北山花岗岩粉中毛细管内扩散

为了解¹²⁹I在我国深地质处置库重点研究区围岩中的迁移行为，为选址预评价提供基础数据，利用批式吸附实验法和改进的毛细管内扩散法研究了碘离子在北山花岗岩粉中的吸附和扩散行为，分析了不同控制条件对碘离子的表观扩散系数(D_a)的影响。结果表明：在固液比为20 g/L，碘离子在北山花岗岩粉上的吸附几乎可以忽略；扩散实验中¹²⁵I^-的D_a值为8.2×10^-11~1.4×10^-9 m²/s，表明碘离子在压实北山花岗岩岩粉中的扩散速率很快；¹²⁵I^-的D_a值随扩散温度的升高而变大，随扩散源液离子强度的增加而变大，随同位素载体浓度的升高而变大，¹²⁵I^-的扩散速率随溶液pH值的上升整体有减小的趋势。

Diffusion of 125I in Compacted Beishan Granite Research of Capillary In-Diffusion Method

In order to understand the migration behavior of ¹²⁹I in the host rock of China’s key potential deep geological repository, and to provide basic data for the pre-safety assessment of the site, the effect of different experimental conditions on the adsorption and diffusion of iodine ion was investigated using a batch sorption method and a modified capillary in-diffusion method. The results suggest that the adsorption of iodide onto Beishan granite is almost negligible under solid/liquid ratio of as high as 20 g/L. According to the capillary experimental results, D_a values of ¹²⁵I^- are between 8.2×10^-11 and 1.4×10^-9 m²/s, which suggests that the diffusion rate of iodide ion in compacted Beishan granite powder is very high. There is a positive correlation between the D_a with temperature, isotopic carrier concentration and ionic strength, which can be explained by Brownian motion and electrical double layer structure of granite surface. While D_a value of ¹²⁵I^- witness an overall decrease with the increase of pH values due to the granite surface charge. As can be seen, the capillary method is a fast and easy method which can be used to investigate the migration of radionuclide in compacted mineral powders.