Transport simulation of Pu through fractured media based on continuous time random walk model
HUANG Shi-qi1, HU Li-tang1, LIU Dong-xu2, LIN Jian-feng2, TIAN Lei1, WANG Dao1
1. College of Water Sciences, Beijing Normal University, Engineering Research Center of Groundwater Pollution Control and Remediation of Ministry of Education, Beijing 100875, China; 2. Northwest Institute of Nuclear Technology, Xi'an 710024, China
Abstract：Non-Fickian dispersion occurs in the migration of nuclides in groundwater, which is influenced by geological media heterogeneity and physicochemical processes. To improve the accuracy of the simulation of this phenomenon, an alternative model is required. To analyze Pu (plutonium) migration in one-dimensional fractured rock columns, we employed the continuous time random walk (CTRW) model together with the traditional advection-dispersion equation (ADE) to effectively represent Pu breakthrough curves (BTCs). The goodness of fit and feasibility of the ADE, CTRW-TPL, CTRW-TPLA, and CTRW-ETA models were later compared to identify the superior model for simulating Pu transport in fractured media with varying colloidal concentrations. The results indicated that the CTRW-TPL model, which incorporated adsorption, outperformed the traditional ADE in describing non-Fickian migration characteristics. Although the CTRW-ETA model lacked comprehensive migration characterization, its inversion process was more feasible. Furthermore, the migration capacity of Pu in fractured media was significantly enhanced due to colloidal effects. However, beyond a certain concentration threshold, the migration capacity of Pu decreased with increasing colloidal concentrations. Regarding the theoretical framework of the CTRW model, our analysis showed that the generalized transport velocity and dispersion coefficient first increased and then decreased, while the average adsorption rate of solute particles first decreased and then increased. These findings serve as a valuable reference for future research on the parameters of the CTRW model in fractured media.
黄诗棋, 胡立堂, 刘东旭, 林剑锋, 田蕾, 王道. 裂隙介质中Pu迁移的连续时间随机游走模拟[J]. 中国环境科学, 2023, 43(12): 6321-6328.
HUANG Shi-qi, HU Li-tang, LIU Dong-xu, LIN Jian-feng, TIAN Lei, WANG Dao. Transport simulation of Pu through fractured media based on continuous time random walk model. CHINA ENVIRONMENTAL SCIENCECE, 2023, 43(12): 6321-6328.
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