摘要
核素在基质中的运移主要受基质的孔隙度、渗透率和扩散系数的影响,其数值越大,核素运移速率越大。基质吸附对核素运移起到一定的阻滞作用,而核素238 U衰变系数对核素运移的影响不大。在其他条件相同的情况下,弥散度增大,核素会迁移得更远。基于这种原理,以四川某拟选核电站厂址所处水文地质环境为基础,以弥散度的差异为前提,运用弥散度分维方程的方法,并辅以Visual MODFLOW数值模拟的手段,对核素238 U在高透水带的冲积覆盖层中与低透水带的基岩中平面和垂向上迁移速率的差异性进行了研究。结果表明:在弥散度较大的孔隙介质中,核素在平面上迁移的速率快,污染面积较大;但在弥散度较小的裂隙较为不发育的基岩中,核素在垂向上的迁移表现较为明显。
The migration of nuclide in matrix is affected by the porosity, permeability and diffusion coeffi- cient of the matrix. The larger these parameters are, the faster the nuclide migration speed is. The nuclide migration is retarded by the matrix sorption to some extent but not much influenced by the decaying coeffi- cient of nuclide Uranium-238. Under the same conditions, the migration distance of nuclide is longer when the macrodispersivity coefficient increases. Based on this principle,this study explores the difference of mi- gration rate of nuclide Uranium-238 in horizontal and vertical direction in the alluvial layer of high permeable zone and the bedrock of low permeable zone. The research is based on the hydrogeological environment of the proposed site of a nuclear power station in Sichuan and on the premise of the difference of macrodisper- sivity coefficient using the method of macrodispersivity of fractal equations and Visual MODFLOW numeri- cal modelling. The results show that the nuclide migration rate in horizontal direction is faster and the pol- lution area of nuclide is larger in pore medium with larger macrodispersivity coefficient. But the nuclide mi- gration in vertical direction is obvious in bedrock with smaller macrodispersivity coefficient and less devel- opment fissures.
出处
《安全与环境工程》
CAS
2015年第6期57-61,66,共6页
Safety and Environmental Engineering
