极端条件下核电用法兰密封系统的完整性及其评价方法研究

Around the problems of the security design and reliable operation of the flange sealing systems in nuclear power under extreme conditions, such as high temperature and pressure, complex dynamic loading and radiation, with the goal of establishing the analysis and design approach of Metal to Metal Contact (MMC-type) flange sealing system's integrity (structure intergrity and sealing tightness) and the on-line evaluation method based on "Operational Modal", three key questions will be deeply studied in this research work. Firstly, to explore the mechanism of MMC-type flange sealing system under extreme conditions with the research of nonlinearity and hysteresis of gaskets, non-linear contact problem of flanges, screw loosening mechanism and radiation resistance performance of joints; Secondly, to study the systematic evolution of damage and failure mechanism, including destruction of structures and failure of sealing under extreme conditions, and coupling calculations among liquid-solid-gas. And then to establish the time-dependent structure and sealing failure modes of the flange sealing system. Thirdly, to study how to extract the correct dynamic parameters of nuclear pipeline system in service from a large number of complex signals with the use of advanced testing and analysis techniques (Operational Modal Analysis). And then to reveal the essential relationship between failure modes and modal parameters of flange sealing systems. To establish evaluation index of the state of flange sealing integrity, and to form evaluation method based on "Operational Modal". Through four years of study, try to get a breakthrough on the theory, design analysis and on-line evaluation of flange sealing systems' integrity under extreme conditions, and then to lay the foundation for the safe operation of pipeline systems in nuclear power.

围绕高温高压、复杂动载和辐射等极端条件下核电用法兰密封系统安全设计和可靠运行难题，以建立金属与金属接触（MMC）型法兰系统完整性（结构完整性和紧密性）的分析设计方法和基于工作模态的在线评价方法为目标，重点突破三个关键：通过对垫片的非线性和迟滞性、法兰接触非线性、螺纹松动机理、耐辐射性等的研究，探索MMC型法兰系统的密封机理；进行系统的损伤演化规律和失效机理研究，包括极端条件下结构破坏行为、密封失效机理及液固气多相耦合计算，建立与时间相关的结构失效和泄漏模型；利用先进测试和分析技术，研究在役条件下从大量错综复杂的信号中提取和识别核电密封系统模态参数的方法（工作模态分析），揭示模态参数与密封失效模式的内在联系，建立法兰系统完整性评价指数，形成基于工作模态的完整性评价方法。通过四年研究，争取在极端条件下法兰密封系统的理论研究、设计分析及在线评价方面取得突破，为核电管路安全运行奠定基础。

本课题以核电常用的金属与金属接触型(MMC)螺栓法兰接头为研究对象,针对其在高温高压和复杂动载条件下的安全设计和可靠运行难题，以建立基于“零泄漏”的设计方法和基于工作模态的工程评价方法为目标，重点解决了以下问题：通过对MMC型石墨密封垫的综合性能及其测试方法的研究以及MMC型法兰接头拧紧方法的优化设计，获得了MMC法兰系统密封机理，并揭示了其相比于浮动型法兰接头具有优异密封性能的内在原因；通过法兰密封系统在高温和温度谱、复杂外载荷作用下的损伤演化规律和失效机理研究，建立了法兰系统结构完整性和密封性能随时间的演化机理和失效机制；利用先进测试和分析技术，研究了在带法兰接头的管路中提取系统的动态特性参数的方法，并针对MMC型法兰密封系统建立了动态安全指标体系，探索了法兰密封系统完整性状态评价指数，形成基于工作模态的法兰密封系统完整性评价方法。通过本课题的研究，核电法兰密封系统在高温高压、复杂动载等条件下的理论研究、设计分析及工程评定方面都取得突破，为核电管路安全运行奠定基础。