高放废物地质处置环境中膨润土胶体特性对铜点蚀生长/消亡的作用机制

在高放废物地质处置环境中，点蚀行为是威胁铜处置罐安全服役的重要形式，而点蚀坑的生长/消亡倾向是决定处置罐是否将快速穿孔失效的关键因素。铜点蚀的生长/消亡倾向主要决定于点蚀坑内/外腐蚀产物的性质，及其对腐蚀传质过程的影响。处置罐缓冲材料膨润土的离子吸附、离子交换、吸水膨胀和低渗透等特性,将极大地影响腐蚀产物的形成以及腐蚀传质的过程。本项目拟采用高庙子钠基膨润土和模拟北山地下水构成腐蚀环境体系，通过离子吸附和离子交换热力学方法、电化学恒电位极化、电化学阻抗谱等方法,研究膨润土胶体特性对铜点蚀传质过程及点蚀生长/消亡倾向的影响；采用XRD, SEM, EDS,红外分析方法分析腐蚀进程中膨润土、铜腐蚀产物的化学组成、形貌和结构变化，说明其与铜点蚀坑生长/消亡倾向的关系；提出高放废物处置环境下铜的点蚀生长/消亡机制。建立腐蚀模型，为我国高放废物处置容器的选材提供理论判据。

Pitting behavior is an important form of threat to the safe operation of copper disposal tanks in the high-level radioactive waste geological disposal environment. The growth and extinction tendency of pitting pits is the key factor to decide whether the disposal tank will be rapidly perforated. The growth and extinction tendency of copper pitting mainly depends on the properties of the pitting inner / external corrosion product and its influence on the mass transfer process. The features of ionic adsorption, ion exchange, expansion upon imbibing water and very low permeability of bentonite in the disposal of the buffer material will greatly affect the formation of corrosion products and the process of mass transfer. In this project, the effects of bentonite on the mass transfer process of copper pitting and the tendency of pitting growth / extinction will be studied by thermodynamics of ionic adsorption, ion exchange, electrochemical polarization and EIS monitoring methods. XRD, SEM, EDS and infrared analysis will be used for analyzing the evolution of the compositions and morphologies and structures of the bentonite and corrosion products of copper pitting. It will explain the correlations between the features of GMZ sodium bentonite and the tendency of growth/extinction of copper pitting in Beishan geological underground water, which is the scientific basis for determining the feasibility of manufactureing the HLW canister.