摘要
简要介绍了人工喷淋条件下在非饱和黄土中进行的核素迁移实验。实验所用示踪剂为90Sr和237Np、238Pu、241Am等超铀核素,示踪源是上述示踪剂的硝酸盐溶液与石英砂的均匀混合物;石英砂的粒径在0.2～0.45mm之间;示踪源层尺寸为120cm×50cm,厚0.7cm,挖坑浅埋于地表下50cm深处;喷淋强度为5mm/h、3h/d;实验历时1078天;每半年在实验坑采集1个土芯样,经切割成样品后送实验室测量样品中核素的比活度,得到核素比活度的纵向分布。本文主要对90Sr的实验结果进行了数据处理,发现90Sr在双层孔隙介质中迁移时,比活度分布出现一“低谷”。文中以90Sr为例讨论了比活度分布“低谷”的成因和特征。由于石英砂层的存在,作为核素迁移载体的水的运移产生绕流,使得90Sr在石英砂层下方的迁移距离远小于85Sr在单一黄土介质中的迁移。
Radionuclide migration experiment in unsaturated loess under sprinkling condition is briefly introduced in this paper.The tracers used for the experiment are 90 Sr and some transuraniums ( 237 Np, 238 Pu, 241 Am ).Tracer source is mixture of nitrate solution of the above-mentioned tracers and quartz sand.Particle sizes of quartz sand range from 0.2 mm to 0.45 mm.Dimension of the tracer layer which was put 50 cm below ground is 120 cm×50 cm and thickness 0.7 cm.Sprinkling rate is 5 mm/h and 3 h/d.A column was collected from experiment pit per half year and cut into samples.Specific activities of radionuclides in samples were measured in laboratory in order to obtain their longitudinal specific activity distribution.The data processing on the results for 90 Sr is conducted in this paper.It is found from the results that lowest valley of specific activity distribution is appeared during radionuclides migration in two-layer porous media.Taking 90 Sr as an example,the forming and characteristics of lowest valley are discussed.Water,which acts as a carrier of radionuclides,formed detouring flow because there exist quartz sand and hence migration distance of 90 Sr below quartz sand layer is much less than that of 85 Sr in single loess medium.
出处
《辐射防护》
CAS
CSCD
北大核心
2005年第4期206-210,共5页
Radiation Protection
