A Calculation of Spatial Range of Colloidal Silicic Acid Deposited Downstream from the Alkali Front
A Calculation of Spatial Range of Colloidal Silicic Acid Deposited Downstream from the Alkali Front
复制标题
碱锋下游胶体硅酸沉积空间范围的计算
DOI：
10.1299/jpes.6.140
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
H. Mimura
中科院分区：
文献类型：
--
作者：
Y. Niibori;K. Iijima;N. Tamura;H. Mimura
由于放射性废物处置库的建造使用了水泥材料，高碱区域向外扩展。在该碱前沿pH值的突然变化除了在流动通道的断裂表面上沉积过饱和单体柠檬酸之外，还产生胶体柠檬酸（聚合柠檬酸）。胶体柠檬酸在固相共存下也以相对小的速率常数沉积。一旦流路表面被无定形二氧化硅覆盖，该表面严重降低放射性核素（RN）的吸附行为。因此，到目前为止，作者已经检查了过饱和柠檬酸的沉积速率。本文总结了在无定形二氧化硅粉共存的各种条件下，由一级反应方程定义的沉积速率常数。然后，使用最小的速率常数（1.0×10 - 5 m/s，在共存的钙离子的1 mM）和一个模拟程序，COLFRAC-MRL，胶体草酸沉积的碱锋下游的空间范围进行了估计。结果表明，胶态草酸在流路中的沉积是造成堵塞的主要原因，流路中裂缝的空间变化范围在30 m左右，岩石基质的空间变化范围在几cm以内。
A high alkali domain spreads out due to the use of cement materials for the construction of the repository of radioactive wastes. Sudden change of pH at this alkali front produces colloidal silicic acid (polymeric silicic acid) in addition to the deposition of supersaturated monomeric silicic acid onto the fracture surface of flow-pathway. The colloidal silicic acid also deposits with relatively small rate-constant in the co-presence of solid phase. Once the flow-path surface is covered with the amorphous silica, the surface seriously degrades the sorption behavior of radionuclides (RNs). Therefore, so far, the authors have examined the deposition rates of supersaturated silicic acid. This study summarized the deposition rate-constants defined by the first-order reaction equation under various conditions of co-presence of amorphous silica powder. Then, using the smallest rate-constant (1.0×10 m/s in the co-presence of calcium ions of 1 mM) and a simulation code, COLFRAC-MRL, the spatial range of colloidal silicic acid deposited downstream from the alkali front was estimated. The results suggested the clogging caused by the deposition of colloidal silicic acid in flow-path. The altered spatial range in the flow-path was limited to around 30 m in fracture and to several centimeters in rock matrix.