开挖损伤区(EDZ)对核素迁移的影响

Review on the Influence of Excavation Damage Zone(EDZ)on Nuclide Migration

随着核电的发展,核电站产生的乏燃料处理处置受到了大众的高度关注。通过对嬗变法、稀释法和隔离法等方法的综合对比,目前,高放废物深地质处置是国内外公认处理核废物的最佳办法。在处置库建造阶段,由于开挖使得围岩中应力重新分布,围岩发生扰动,岩体内部原生裂隙出现扩展、连通,产生新生的微裂隙,岩体的渗透系数变大,这种区域即为开挖损伤区(excavation damaged zone,EDZ)。EDZ位于高放废物处置库工程屏障和远场围岩中间,是放射性核素迁移的重要迁移通道。地下水流经深部围岩裂隙与扰动层破碎带发生水岩反应导致成分发生变化,进而影响高放废物中核素释出速率与迁移参数,需要在地下实验室开挖过程中获取大尺度裂隙围岩及扰动层破碎带,建立核素释出和迁移装置,获得地下水侵入深部围岩裂隙与扰动破碎带导致高放废物核素释出与迁移参数变化规律,对于整个地质处置场的安全评价具有重要意义。研究人员通过实验和计算机软件进行模拟分析发现,EDZ区的裂隙水、Eh-pH、裂隙充填物、裂隙中的胶体以及裂隙中的腐殖酸等,均会对核素迁移产生影响。开展EDZ对高放废物体核素源项释放的影响研究和深部围岩条件下核素迁移行为研究,掌握关键核素在深部地质条件下的释出规律及其在EDZ区域和裂隙中的迁移规律,优化迁移模型,将为地下实验室运行阶段开展核素迁移实验提供技术储备,为我国高放废物处置库场址比选、概念设计和安全评价提供技术支撑和科学依据。

With the development of nuclear power,the disposal and disposal of high-level waste generated by nuclear power plants have also received great attention from the public.After a comprehensive comparison of methods such as transmutation method,dilution method and isolation method,at present,deep geological disposal of high-level radioactive waste is recognized as the best method for nuclear waste at home and abroad.During the construction stage of the repository,due to excavation,the stress in the surrounding rock is redistributed and the surrounding rock is disturbed.The original fissures in the rock mass expand and connect,resulting in new micro-cracks,and the permeability coefficient of the rock mass becomes larger.It is the excavation damaged zone(EDZ).EDZ is located between the engineering barrier of the high-level radioactive waste repository and the remote surrounding rock,and is an important channel for the migration of radionuclides.Groundwater flowing through the deep surrounding rock fissures and the fracture zone of the disturbed layer cause water-rock reaction to change the composition,which affects the release rate and migration parameters of radionuclides in the high-level glass body.It is necessary to obtain large-scale fissures during excavation in the underground laboratory.Rock and disturbed layer fracture zone,establish nuclide release and migration devices,and obtain groundwater intrusion into deep surrounding rock fissures and disturbed fracture zones that lead to the release and migration parameters of high-level radioactive glass nuclide,which is useful for the safety evaluation of the entire geological disposal site.Researchers conducted simulation analysis through experiments and computer software and found that fissure water,Eh-pH,fissure fillings,colloids in the fissures,and humic acid in the fissures in the EDZ zone all affect the migration of nuclide.Carrying out research on the effect of EDZ on the release of nuclide source terms in high-level radioactive waste and studying on the migration behavior of nuclide under deep surrounding rock conditions,and grasping the release law of key nuclides under deep geological conditions and their migration in EDZ areas and fissuring laws and optimizing migration models will provide technical reserves for nuclear in situ migration experiments during the operation phase of underground laboratories,and provide technical support and scientific basis for the site selection,conceptual design and safety evaluation of my country’s high-level radioactive waste repository.