90Sr在微风化二长花岗岩中迁移实验及模拟研究  

Experiment and Simulation Study on Migration of 90Sr in Weakly Weathered Granite

作　　者：王瑞青 陈超[1] 谢添 陈文杰 朱君[1] WANG Rui-qing;CHEN Chao;XIE Tian;CHEN Wen-jie;ZHU Jun(Department of Nuclear Environmental Science,China Institute for Radiation Protection,Taiyuan 030006,China)

机构地区：[1]中国辐射防护研究院核环境科学研究所,山西太原030006

出　　处：《核化学与放射化学》2024年第3期258-263,I0003,共7页Journal of Nuclear and Radiochemistry

基　　金：国家重点研发计划项目(2020YFC1806604)。

摘　　要：采用加压的方式,利用动态柱实验方法,通过3H、90Sr在微风化二长花岗岩中的穿透曲线,研究了90Sr在微风化二长花岗岩中的迁移规律,获得90Sr在微风化二长花岗岩中的迁移参数。实验中控制流速为1 mL/h,3H总活度为10^(4)Bq,迁移实验进行了120 h,3H浓度峰值出现在8.0 h,活度浓度峰值为213.4 kBq/L,穿透曲线无明显拖尾现象;90Sr总活度为5×10^(4)Bq,迁移实验进行了132 d,90Sr浓度峰值出现在27.4 d,活度浓度峰值为46.26 kBq/L,浓度下降阶段呈现明显的拖尾现象。利用数值模拟方法,基于3H的穿透曲线计算得到微风化二长花岗岩的垂向弥散度为3.03 cm;对比了平衡模型、双点吸附模型、两区模型、双点吸附两区模型四种模型下90Sr在微风化二长花岗岩中的迁移拟合结果,发现四种模型拟合结果相差较大,其中双点吸附两区模型通过引入非流动区含水量、溶质交换一级速率系数、非平衡吸附一级速率系数等参数能够更好地描述核素在微风化二长花岗岩介质迁移过程中的拖尾现象。结果表明:90Sr在微风化二长花岗岩中的吸附分配系数为1.23 mL/g,溶质交换一级速率系数为0.227/d,非平衡吸附一级速率系数为0.118/d。In this experiment,the migration of 90Sr in the weakly weathered granite was studied by using the penetration curve of 3H and 90Sr with the method of dynamic column experiment.The migration parameters of 90Sr in the weakly weathered granite were obtained.The flow rate was set at 1 mL/h during the test.With 104 Bq 3H,the migration test has been carried out for 120 h.The peak activity concentration appeares at 8.0 hour,with the peak activity concentration of 213.4 kBq/L,and the penetration curve of 3H has no obvious tailing phenomenon.With 5×10^(4)Bq 90Sr,the migration test has been carried out for 132 d.The peak activity concentration appeares on 27.4 day,with the peak activity concentration of 46.26 kBq/L,and the concentration of 90Sr shows an obvious tailing phenomenon in the decreasing stage.By means of numerical simulation,the vertical dispersion of weakly weathered granite is 3.03 cm.By comparing the fitting results of 90Sr in weakly weathered granite under the following four models:equilibrium model,two-site sorption model,dual-porosity model,and dual-porosity model with two-site sorption,it is found that the fitting results of the four models are quite different.Dual-porosity model with two-site sorption can better explain the non-equilibrium adsorption phenomenon during the migration of nuclides in the weakly weathered granite by introducing the water content in the non-moving region,the first-order rate coefficient of solute exchange and the first order rate coefficient of non-equilibrium adsorption.The results show that distribution coefficient of 90Sr in weakly weathered granite is 1.23 mL/g,the first order rate coefficient of solute exchange is 0.227/d,and the first order rate coefficient of non-equilibrium adsorption is 0.118/d.

关 键 词：核素迁移 花岗岩 非平衡吸附 双点吸附两区模型 一级速率系数 90Sr 

分 类 号：X591[环境科学与工程—环境工程]