Diffusion coefficients for Na⁺ was measured in low-permeability samples (diameter of 3 cm and average length of 7 cm) from the deep disposal site of the Siberian Chemical Combine (SCC) using the end-diffusion technique. The direction of diffusion was perpendicular to the direction of bedding. Special equipment was designed and constructed for the experiment. Two types of concentration observations were used. For non-sorbing Na⁺, EC sensors and the length distribution of sorbed elements were used. The synthetic solution used in the experiments was a model of the low-activity contaminant of the SCC and consisted of NaNO₃ (25 g/L) and nitrate compounds of Cs⁺, Ni²⁺, Co²⁺, and Sr²⁺ (100 mg/L each). The measured values of the effective diffusion coefficients D_e for Na⁺ from 1.92 × 10⁻¹¹ to 1.70 × 10⁻¹⁰ m²/s. The microstructure was studied with X-ray microtomography for the same cores. Image shooting was performed on undisturbed microsamples with a size of 0.91³ mm (700³ vox). Spatial correlation analysis was performed after the binarization of each obtained 3-D structure. This analysis showed that the spatial correlation scale of the indicator variogram is considerably smaller than the microsample length. Then, a numerical simulation of the Laplace equation with binary coefficients for each microsample was performed. The results were analysed in the form of a plot of the tortuosity versus the porosity. Pore-scale simulations show a nonlinear decrease in the tortuosity with decreasing porosity. Exponential values in the range between 1.8 and 2.4 were found by fitting this graph with Archie's model. Anisotropic tortuosity is also detected in the horizontal and vertical directions. The diffusion coefficients of non-sorbing Na⁺ measured in this study agree with those of the pore-scale diffusion simulation of the microtomography data.

Na ^{+ 的}扩散系数是使用末端扩散技术在来自西伯利亚化学联合体 (SCC) 深部处置场的低渗透性样品（直径为 3 厘米，平均长度为 7 厘米）中测量的。扩散方向垂直于层理方向。为实验设计并建造了专用设备。使用了两种类型的浓度观察。对于非吸附 Na ⁺，使用 EC 传感器和吸附元素的长度分布。实验中使用的合成溶液是 SCC 低活性污染物的模型，由 NaNO ₃ (25 g/L) 和 Cs ⁺、Ni ²⁺、Co ²⁺和 Sr 的硝酸盐化合物组成²⁺（每个 100 毫克/升）。有效扩散系数的测量值d _Ë的Na ⁺从1.92×10 ^-11到1.70×10 ^-10 米² /秒。用 X 射线显微断层摄影术研究相同岩心的微观结构。图像拍摄是在大小为 0.91 ³  mm (700 ³ vox) 的未受干扰的微样品上进行的。在对每个获得的 3-D 结构进行二值化之后进行空间相关分析。该分析表明，指标变异函数的空间相关尺度远小于微样本长度。拉普拉斯方程的数值模拟对每个微样品进行二进制系数。结果以曲折度与孔隙度的关系图的形式进行分析。孔隙尺度模拟显示，随着孔隙度的降低，曲折度呈非线性降低。通过将该图与 Archie 模型拟合，可以找到介于 1.8 和 2.4 之间的指数值。在水平和垂直方向也检测到各向异性弯曲度。本研究中测量的非吸附 Na ⁺的扩散系数与显微断层扫描数据的孔隙尺度扩散模拟结果一致。