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首页> 外文期刊>Transport in Porous Media >The Influence of Hyper-Alkaline Leachate on a Generic Host Rock Composition for a Nuclear Waste Repository: Experimental Assessment and Modelling of Novel Variable Porosity and Surface Area
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The Influence of Hyper-Alkaline Leachate on a Generic Host Rock Composition for a Nuclear Waste Repository: Experimental Assessment and Modelling of Novel Variable Porosity and Surface Area

机译：高碱性渗滤液对核废料储存库通用主体岩石组合物的影响：新型可变孔隙度和表面积的实验评估和建模

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Deep geological disposal is the preferred solution for long-term storage of radioactive waste in many countries. In a deep repository, cementitious materials are widely used in the structure and buffer/backfill of the repository for the stabilisation of the hazardous materials. The cement acts as a physical barrier and also contributes chemically to waste containment by buffering the groundwater to a high pH, limiting the solubility of many radionuclides. This paper describes an experimental and modelling study which evaluates the geochemical interaction between young cement leachate (YCL, pH = 13) and a generic hard rock (in this case Hollington sandstone, representing a 'hard' host rock) during permeation with the leachate, as it drives mineralogical changes in the system. One-dimensional reactive transport was modelled using a mixing cell approach within the PHREEQC geochemical code to identify the essential parameters and understand and scale up the effect of variations in these parameters on the observed geochemical processes. This study also focused on the effects of variable porosity, reactive surface area and pore volume on improving the modelling of rock alteration in the system compared to conventional models that assume constant values for these properties. The numerical results showed that the interaction between the injected hyper-alkaline leachate and the sandstone sample results in a series of mineralogical reactions. The main processes were the dissolution of quartz, kaolinite and k-feldspar which was coupled with the precipitation of calcium silicate hydrate gel and tobermorite-14A (C-S-H), prehnite (hydrated silicate), saponite-Mg (smectite clay) and mesolite (Na-Ca zeolite). The simulation showed that the overall porosity of the system increased as primary minerals dissolve and no stable precipitation of the secondary C-S-H /C-A-S-H phases was predicted. The variable porosity scenario provides a better fitting to experimental data and more detailed trends of chemistry change within the column. The time and the number of moles of precipitated secondary phases were also improved which was related to greater exposure surface area of the minerals in the sandstone sample to the YCL.
机译：深层地质处置是许多国家的放射性废物长期储存的首选解决方案。在深度储存库中，胶凝材料广泛用于储存库的结构和缓冲器/回填，以稳定危险材料。水泥用作物理屏障，并且还通过将地下水缓冲到高pH，限制了许多放射性核素的溶解度来用化学方式贡献。本文介绍了一种实验和建模研究，可评估年轻水泥渗滤液（YCL，pH = 13）和通用硬岩之间的地球化学相互作用（在这种情况下Hollington砂岩，在渗透渗滤液期间代表一个“硬”宿主岩石），随着它推动系统中的矿物学变化。使用Phreeqc地球化学代码内的混合电池方法进行建模一维反应传输，以识别基本参数，并了解这些参数在观察到的地球化学过程中的变化的影响。该研究还集中于可变孔隙率，反应性表面积和孔体积对改善系统中岩石变化建模的影响，与这些特性持续值的常规模型相比。数值结果表明，注射的超碱性渗滤液与砂岩样品之间的相互作用导致一系列矿物学反应。主要方法是石英，高岭石和K-Feldspar的溶解，其与硅酸钙水合物凝胶和Tobermorite-14a（CSH），前（水合硅酸盐），皂苷-mg（蒙脱石粘土）和亚斯莫钛（Na -CA沸石）。模拟表明，由于初级矿物溶解，并且预测了系统的整体孔隙率随着初级矿物质溶解，并且预测了二次C-S-H / C-A-S-H相的稳定沉淀。可变孔隙度方案提供了更好的实验数据和柱内化学变化的更详细趋势。还改善了沉淀的二阶段的摩尔数和摩尔数，其与砂岩样品中矿物质的更大曝光表面积与YCL有关。

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