锆合金钝化膜的形成及其失效的电化学基因研究

That how to improve the safety of nuclear fuel cladding is the most urgent engineering problems to be solved in current nuclear industry. Irradiation corrosion, with the electrochemical process in essence, is the main failure form of zirconium alloys. The scarce knowledge on the failure of the electrode reaction kinetics at micro levels, however, seriously restricted the development of new alloys and the evaluation of their lifespan. The key technical issue involved is the lack of effective corrosion characterization methods with trans-scale and multi-parameter, which brought huge difficulties to establish a quantitative structure-activity relationship. In this project, a new technique based on the scanning needlepoint Raman - electrochemical high-throughput characterization at nano-scale is put forward for the first time to investigate the passive formation and failure of zirconium alloys, and a new viewpoint of conjugate cathodic hydrogen reduction system using electrons as reactant for the search of corrosion genes is also suggested. In the upcoming project, we will first understand the potential distribution, the polarity changes of the phase, crystal plane and grain boundary as well as the initial corrosion mechanism of zirconium alloys before and after charge particle irradiation; Secondly, analysis will be conducted on the electrochemical difference of the grains and grain boundaries, defect characteristics and phase evolution of passivation film under growth stress; Finally, the relationship between conductivity, defect concentration and ionic diffusion was established on the basis of the carrier transport characteristics of the Schottky junction located at the interface of passivation membrane. And on the basis of the cask effect for the failure of passivation film will be summarized and the electrochemical corrosion defect genome system will be established. The research results will lay a solid theoretical foundation for the design of new zirconium alloys with excellent radiation-tolerant corrosion and for lifetime management as well as provide important technical support for the safe operation of nuclear power plants.

提高核燃料包壳的寿命和安全性是核电工业亟待解决的工程问题。辐照腐蚀是锆合金失效的主要形式，本质属于电化学过程，但对其失效的微观电极反应动力学基本科学问题认识的不足严重制约了新合金的研发及寿命评价。涉及的关键技术问题是缺乏跨尺度多参数的表征手段，难以建立量化的腐蚀构效关系。本申请首次提出基于纳米针尖拉曼-电化学扫描高通量表征锆合金钝化膜的形成及其失效的新方法，并从电子作为反应剂的阴极还原共轭体系新角度寻找腐蚀基因。首先比较锆合金的晶相、晶面及晶界在粒子辐照前后的电位分布、极性变化及初始腐蚀机理；其次研究应力作用下钝化膜的物相演变、缺陷特征及极化差异；最后基于肖特基结特性阐明钝化膜的载流子输运行为，建立电导、缺陷及离子扩散的关联，揭示钝化膜失效的短板效应，获得缺陷电化学腐蚀基因的系统认识。研究结果将为抗辐照腐蚀新锆合金的设计和寿期管理奠定坚实的理论基础，并为核电站的安全运行提供重要的技术支撑。

提高核燃料包壳的寿命和安全性是核电工业亟待解决的工程问题。辐照腐蚀是锆合金失效的主要形式，本质属于电化学过程，但对其失效的微观电极反应动力学基本科学问题认识的不足严重制约了新合金的研发及寿命评价。本项目通过高温高压水原位电化学及显微拉曼为主的研究手段对我国自主开发的新锆合金进行了研究和评价，考察辐照对锆合金钝化膜氢渗透的影响，以及对钝化膜失效的缺陷进行溯源。取得了以下研究结果：（1）研建了具备水化学监控功能的高通量原位电化学测量装置，为反应堆运行工况下燃料元件包壳腐蚀行为的在线监控和腐蚀机理研究提供了新研究平台。（2）建立了基于μ-Raman光谱仪-LCSM（激光共聚焦显微镜）-SEM（扫描电镜）联动分析技术的锆合金氧化膜研究方法，基于该方法在首次实现了腐蚀氧化膜中四方相等效厚度、微区应力-物相耦合分布等分析。（3）获得了合金长达350天的原位电化学监控结果，包括腐蚀电位、电化学阻抗谱，得到了氧化膜的原位物理性质演变规律，包括氧化膜电阻率、氧离子扩散系数，初步阐明了腐蚀反应动力学机制。（4）通过纳米探针示踪方法，基本建立了腐蚀缺陷的定位方法，为腐蚀基因的溯源提供了新手段。研究结果为抗辐照腐蚀新锆合金的设计和寿期管理奠定坚实的理论基础，并为核电站的安全运行提供重要的技术支撑。项目研究发表 SCI 收录论文 22 篇，EI 论文 1 篇，申请发明专利 3 项。培养研究生4名, 毕业研究生2名。