碱性溶液对高庙子膨润土缓冲性能的影响  

Effect of Alkaline Solution on Buffering Properties of GMZ Bentonite

作　　者：童艳梅 张虎元[1,2] 李雪婷 李小雅 TONG Yanmei;ZHANG Huyuan;LI Xueting;LI Xiaoya(School of Civil Engineering and Mechanics,Lanzhou University,Lanzhou,Gansu 730000,China;Key Laboratory of Mechanics on Disaster and Environment in Western China,The Ministry of Education,Lanzhou University,Lanzhou,Gansu 730000,China)

机构地区：[1]兰州大学土木工程与力学学院,甘肃兰州730000 [2]兰州大学西部灾害与环境力学教育部重点实验室,甘肃兰州730000

出　　处：《世界核地质科学》2023年第S01期607-613,共7页World Nuclear Geoscience

基　　金：国家自然科学基金项目(编号:41972265)资助。

摘　　要：膨润土是高放废物地质处置库中重要的缓冲屏障。但在处置库运营过程中,地下水溶蚀衬砌混凝土产生的强碱性溶液会扩散进入膨润土缓冲屏障,使屏障性能发生退化。本研究设计了专门的接触扩散装置,模拟研究碱溶液在压实高庙子膨润土试样内的扩散过程及对膨润土矿物和微观结构的影响。试验发现随着反应时间增长,膨润土的缓冲能力会下降。膨润土中主要矿物蒙脱石的溶解与碱溶液pH值、温度、时间成正相关关系。相同pH值的KOH和NaOH溶液对膨润土具有相似的影响,从微观结构试验观察到蒙脱石的溶解使膨润土完整性丧失,产生大量的裂隙进而加速溶蚀进程。同时,与KOH溶液反应后观察到新生成的伊利石微晶,表明蒙脱石的溶解和相变是直接导致膨润土缓冲性能退化的主要原因。Bentonite is an important buffer barrier in deep geological repository of high-level radioactive waste.During the operation of repository,the highly alkaline solution generated by groundwater erosion of the lining concrete will diffuse into the bentonite buffer barrier,resulting in the degradation of barrier property.In this study,a special contact diffusion device was designed to simulate the diffusion process of alkaline solution in compacted GMZ bentonite and the changes of bentonite mineral and microstructure were analyzed.It was found that the buffering capacity of bentonite decreases as the reaction time increases.The dissolution of montmorillonite,the main mineral in bentonite,is positively correlated with the alkaline solution pH,temperature and time.The same pH of KOH and NaOH solutions have similar effects on bentonite,and it was observed from microstructure tests that the dissolution of montmorillonite causes the loss of bentonite integrity,generating a large number of fissures and thus accelerating the dissolution.In addition,newly generated illite microcrystals were observed after reaction with KOH solution,indicating that the dissolution and transformation of montmorillonite is the main reason for the degradation of bentonite buffering properties.

关 键 词：高放废物处置 膨润土 蒙脱石 碱溶液 溶解 

分 类 号：TL942[核科学技术—辐射防护及环境保护]