Sophisticated modeling of the migration of sorbing radionuclides in compacted claystones is needed for supporting the safety analysis of deep geological repositories for radioactive waste, which requires robust modeling tools/codes. Here, a benchmark related to a long term laboratory scale diffusion experiment of cesium, a moderately sorbing radionuclide, through Opalinus clay is presented. The benchmark was performed with the following codes: CORE^2DV5, Flotran, COMSOL Multiphysics, OpenGeoSys-GEM, MCOTAC and PHREEQC v.3. The migration setup was solved with two different conceptual models, i) a single-species model by using a look-up table for a cesium sorption isotherm and ii) a multi-species diffusion model including a complex mechanistic cesium sorption model. The calculations were performed for three different cesium boundary concentrations (10⁻³, 10⁻⁵, 10⁻⁷ mol / L) to investigate the models/codes capabilities taking into account the nonlinear sorption behavior of cesium. Generally, good agreement for both single- and multi-species benchmark concepts could be achieved, however, some discrepancies have been identified, especially near the boundaries, where code specific spatial (and time) discretization had to be improved to achieve better agreement at the expense of longer computation times. In addition, the benchmark exercise yielded useful information on code performance, setup options, input and output data management, and post processing options. Finally, the comparison of single-species and multi-species model concepts showed that the single-species approach yielded generally earlier breakthrough, because this approach accounts neither for cation exchange of Cs⁺ with K⁺ and Na⁺, nor K⁺ and Na⁺ diffusion in the pore water.

需要对压实粘土岩中吸附放射性核素的迁移进行复杂建模，以支持放射性废物深层地质处置库的安全分析，这需要强大的建模工具/代码。在这里，介绍了与铯（一种中等吸收性放射性核素）通过 Opalinus 粘土的长期实验室规模扩散实验相关的基准。使用以下代码执行基准测试：CORE ^2DV5、Flotran、COMSOL Multiphysics、OpenGeoSys-GEM、MCOTAC 和 PHREEQC v.3。迁移设置由两种不同的概念模型解决，i) 使用铯吸附等温线查找表的单物种模型和 ii) 包括复杂机械铯吸附模型的多物种扩散模型。对三种不同的铯边界浓度（10 ^-3、10 ^-5、10 ^-7 mol / L) 来研究考虑铯的非线性吸附行为的模型/代码能力。一般来说，可以实现单物种和多物种基准概念的良好一致性，但是，已经确定了一些差异，尤其是在边界附近，必须改进代码特定的空间（和时间）离散化以在花费更长的计算时间。此外，基准测试产生了关于代码性能、设置选项、输入和输出数据管理以及后处理选项的有用信息。最后，单物种和多物种模型概念的比较表明，单物种方法通常产生较早的突破，因为这种方法既不考虑 Cs ^{+ 的}阳离子交换K ⁺和 Na ⁺，也没有 K ⁺和 Na ⁺在孔隙水中的扩散。