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
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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高碱性渗滤液对核废料处置库一般主岩成分的影响：新型可变孔隙率和表面积的实验评估和建模
DOI：
10.1007/s11242-021-01702-2
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发表时间：
2021
影响因子：
2.7
通讯作者：
Baqer Y
中科院分区：
文献类型：
--
作者：
Baqer Y
摘要深部地质处置是许多国家长期储存放射性废物的首选解决方案。在深层储存库中，胶凝材料被广泛用于储存库的结构和缓冲/回填中，以稳定危险材料。这种水泥起到了物理屏障的作用，还通过将地下水缓冲到高pH值来在化学上遏制废物，限制了许多放射性核素的溶解。本文描述了一项实验和模拟研究，该研究评估了年轻的水泥渗滤液(YCL，pH = 13)与普通硬岩(在这种情况下，霍灵顿砂岩代表一种“硬”寄主岩石)在渗滤液渗透过程中的地球化学相互作用，因为它驱动了系统中的矿物学变化。在PHREEQC地球化学程序中使用混合单元方法模拟了一维反应迁移，以确定基本参数，并了解和放大这些参数的变化对观察到的地球化学过程的影响。这项研究还重点研究了可变孔隙率、反应表面积和孔隙体积对改进系统中岩石蚀变模型的影响，而传统模型假定这些属性为恒定值。数值结果表明，注入的超碱性渗滤液与砂岩样品之间的相互作用导致了一系列的矿物学反应。主要过程是石英、高岭石和钾长石的溶解，同时伴随着硅酸钙水凝胶和托贝莫来石-14A(C-S-H)、前驱石(水化硅酸盐)、皂石-镁(蒙脱石粘土)和中沸石(钠钙沸石)的沉淀。模拟结果表明，随着原生矿物的溶解，系统的总孔隙率增加，预计不会有C-S-H/C-A-S-H二次相稳定析出。可变孔隙率情景更好地拟合实验数据和柱内化学变化的更详细趋势。二次相析出的时间和摩尔数也有所改善，这与砂岩样品中矿物对YCL的暴露表面积较大有关。文章要点钙、铝和硅酸盐浓度的下降主要是由于形成了水化硅酸钙和沸石矿物作为二次相。模拟结果表明，随着原生矿物的溶解，体系的总孔隙率增加，预计不会有C-S-H/C-A-S-H次生相的稳定析出；原生矿物的溶解和次生C-S-H相的析出对体系pH值的影响很小，主要受初始流体化学的控制；变孔隙率假设能更好地拟合实验数据和更详细地反映塔内化学变化的趋势。
AbstractDeep 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.Article HighlightsThe drop in calcium, aluminium and silicate concentrations is mainly due to the formation of calcium silicate hydrate and zeolite minerals as secondary phases. 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 dissolution of primary minerals and the precipitation of secondary C–S–H phases had a minimal effect on the pH values, and this was controlled mainly by the initial fluid chemistry.The variable porosity scenario provides a better fitting to experimental data and more detailed trends of chemistry change within the column.
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DOI：
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发表时间：
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影响因子：
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影响因子：
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