^(239)Pu(Ⅳ)在花岗岩裂隙介质中迁移的数值模拟

Numerical Simulation of ^(239)Pu(Ⅳ) Transport in Granite Fissure

基于双重连续介质模型,根据单裂隙岩体核素迁移规律,推导了核素在平行板单裂隙岩体裂隙域和基质域中的迁移方程,并得出了核素在基质域和裂隙域中的相对浓度。模拟过程中选择239 Pu(Ⅳ)作为分析对象,结合研究区渗透系数和分配系数等参数值,分析了研究区花岗岩岩体裂隙域和基质域中相对浓度的分布情况,预测了239Pu(Ⅳ)在裂隙域和基质域中的发展趋势和迁移情况。模拟表明239 Pu(Ⅳ)在基质域内的扩散非常缓慢,经过0.5×105 a,扩散范围仅在毫米量级,而在裂隙域中大约迁移3m,模拟结果表明该花岗岩区域具备处置含239Pu(Ⅳ)等放射性废物的条件。同时讨论了裂隙域水的平均速度、隙宽、渗透系数、基质域和裂隙域内阻滞系数等参数的变化对放射性核素裂隙域迁移情况的影响。

According to the dual continuous medium model, the nuclide transport equations of fissure and matrix are derived in parallel plate single fractured granite based on the nuclide migration rule in this paper, the relative concentrations of nuclide are obtained in fissure and matrix. The ^239Pu（Ⅳ） is selected as the simulation subject, the distributions of relative concentration are analyzed in granite fissure and matrix of the study region, combined with the permeability coefficient, the partition coefficient and other parameters of the study region, and the developing trend and migration of ^239 Pu（Ⅳ） are predicted in fissure and matrix. The simulation shows that this diffusion velocity of ^239Pu（Ⅳ） is very slow, the range of diffusion is only millimeter level after 0. 5 × 10^5 a in matrix, but it is 3 m in fissure. The result shows that this area of the granite meets the condition of radioactive waste disposal containing ^239Pu（Ⅳ） etc. At the same time, the rule of the nuclides migration is discussed due to the variation of some parameters in the fissure, including the average speed of fissure water, gap width, permeability coefficient, radionuclide half-life, retardation factor in matrix and fissure etc.