Modelling iron-bentonite interactions
Modelling iron-bentonite interactions
复制标题
模拟铁-膨润土相互作用
DOI：
10.1016/j.clay.2008.03.011
复制
发表时间：
2010
影响因子：
5.6
通讯作者：
James Wilson
中科院分区：
文献类型：
--
作者：
D. Savage;C. Watson;S. Benbow;James Wilson
在一些高放废物地质处置工程屏障系统（EBS）设计中，铁罐和膨润土的同时存在可能产生化学相互作用，从而影响粘土作为放射性核素迁移屏障的长期性能。自然系统的证据表明，富铁流体的粘土蚀变序列可能通过奥斯特瓦尔德步骤序列进行。计算机代码QPAC已被修改，以纳入成核，生长，前体蚕食，奥斯特瓦尔德熟化过程，以解决膨润土蚀变产物的缓慢增长的问题。这一点，再加上列入铁的腐蚀和扩散的过程中，使调查的一个典型的EBS环境中的膨润土的蚀变的代表性模型。固定矿物表面积的模拟表明，berthiocyanate占主导地位的固体产品组合，菱铁矿取代它在模拟时间大于10,000年。随时间变化的矿物表面积的模拟显示了一个固体蚀变产物的序列，描述为：磁铁矿→cronstedtite→ berthiorite →磁铁矿。使用合理的估计矿物-流体界面自由能，直到5000年的模拟时间，才实现了碳纤维的增长。这一建模工作的结果表明，应通过实验室实验和自然模拟研究的专门方案，加大努力提供铁硅酸盐的关键数据（例如动力学数据、溶解度和矿物-流体界面自由能）。
The presence of both iron canisters and bentonitic clay in some engineered barrier system (EBS) designs for the geological disposal of high-level radioactive waste (HLW) creates the potential for chemical interactions which may impact upon the long-term performance of the clay as a barrier to radionuclide migration. Natural systems evidence suggests that the sequence of alteration of clay by Fe-rich fluids may proceed via an Ostwald step sequence. The computer code QPAC has been modified to incorporate processes of nucleation, growth, precursor cannibalisation, and Ostwald ripening to address the issues of the slow growth of bentonite alteration products. This, together with inclusion of processes of iron corrosion and diffusion, has enabled investigation of a representative model of the alteration of bentonite in a typical EBS environment. Simulations with fixed mineral surface areas show that berthierine dominates the solid product assemblage, with siderite replacing it at simulation times greater than 10,000 years. Simulations with time-dependent mineral surface areas show a sequence of solid alteration products, described by: magnetite→cronstedtite→berthierine→chlorite. Using plausible estimates of mineral-fluid interfacial free energies, chlorite growth is not achieved until 5000 years of simulation time. The results of this modelling work suggest that greater effort should be placed upon providing key data for iron silicates (e.g. kinetic data, solubilities, and mineral-fluid interfacial free energies), through a dedicated programme of laboratory experimental and natural analogue research.