放射性核素在饱和多孔介质原状土中运移机制研究  

Mechanism of Radionuclide Migration on Saturated and Undisturbed Soil Medium

作　　者：陈超[1,2] 谢添[2] 朱君 石云峰[2] 李婷[2] 杨松 张艾明 骆志平[1] CHEN Chao;XIE Tian;ZHU Jun;SHI Yunfeng;LI Ting;YANG Song;ZHANG Aiming;LUO Zhiping(Department of Radiation Safety,China Institute of Atomic Energy,Beijing 102413,China;China Institute for Radiation Protection,Taiyuan 030006,China)

机构地区：[1]中国原子能科学研究院辐射安全研究所,北京102413 [2]中国辐射防护研究院,山西太原030006

出　　处：《原子能科学技术》2022年第12期2625-2635,共11页Atomic Energy Science and Technology

摘　　要：为科学评估处置场及核设施退役治理过程中的长期风险,需了解放射性核素在含水层复杂地质环境中的反应机制和迁移行为。本文通过室内静态批式法及动态原状土柱实验,开展了^(90)Sr、^(137)Cs、^(238)Pu、^(241)Am在饱和多孔介质细砂中的动态迁移转化过程研究,构建了核素在土壤及地下水环境中迁移的理论模型,利用实验手段解析了核素微界面不可逆吸附反应过程,计算了核素迁移浓度分布曲线。结果表明:静态实验^(90)Sr吸附-解吸等温线并不完全重合,且二者之间存在一夹角φ(φ=32.38°),由亚平衡吸附理论可知,^(90)Sr的吸附-解吸过程具有明显的不可逆性,其吸附作用以离子交换反应为主;^(137)Cs、^(238)Pu、^(241)Am的吸附-解吸等温线近乎平行,表现出良好的吸附可逆性,3种核素以表面配合反应为主。对于^(90)Sr,动态柱法非平衡吸附模式考虑了溶解相与吸附相之间的一级速率系数β,计算所得浓度分布曲线与实测浓度分布曲线吻合较好,通过拟合得到^(90)Sr在含水层细砂介质中的分配系数为0.85 mL/g,β为0.16 h^(-1);^(137)Cs、^(238)Pu、^(241)Am在平衡吸附、非平衡吸附两种模式下所得核素浓度分布曲线与实测曲线吻合均较好,拟合分配系数K_(d)依次为4.9×10^(2)、2.1×10^(4)、6.0×10^(3) mL/g,表明核素在土壤介质中的吸附能力越强,其吸附-解吸速率越快,体系反应达到平衡的时间越短,平衡吸附模式与非平衡吸附模式拟合结果越接近。In order to provide technical support and evaluation basis for the development of remediation technology of radioactive contaminated sites and the site selection,design and construction of radioactive waste disposal facilities,the reliable long-term risk assessment for potential nuclear waste repositories and decommissioning of nuclear facilities requires detailed knowledge on the migration behavior of radionuclides in natural,it is necessary to understand the reaction mechanism of radionuclides in the complex geological environment of aquifers.The batch experiments and dynamic undisturbed soil column migration experiments of ^(90)Sr,^(137)Cs,^(238)Pu and ^(241)Am were carried out under saturated steady-state flow conditions in fine sand column,a theoretical model of nuclide migration in soil and groundwater environment was constructed,and the irreversible adsorption reaction mechanism of the micro-interface was studied through static adsorption-desorption and dynamic undisturbed soil column migration experiments,and the environmental migration flux of nuclides was calculated.The static adsorption and desorption experiments adopt batch method,and the test medium is fine sand with saturated porous media from an arid mining area in Gansu Province.The fine sand and soil samples according to the solid-liquid ratio of 1 g∶9 mL were added into the centrifuge tube,and the nuclide activity concentration was measured after adsorption and desorption equilibriums to obtain the adsorption and desorption isotherms.Dynamic column method used undisturbed soil to ensure the continuity of soil sample medium,original connectivity of void channels and authenticity of stratum.The design and advantages of dynamic column method is to take into account various physical,chemical and biogeochemical reaction processes and complex migration paths of tracers during migration in soil.And the dynamic migration and transformation process of ^(90)Sr,^(137)Cs,^(238)Pu and ^(241)Am were studied in saturated porous media with anisotropic time-va

关 键 词：放射性核素 不可逆吸附 运移 非平衡模式 

分 类 号：X52[环境科学与工程—环境工程]