高温气冷堆金属堆内构件散体结构的抗震性能研究

Unlike the internals in traditional pressurized water reactor, the internals in high temperature gas-cooled reactor (HTR) are piled up by tens of thousands of ceramic components, which are supported and constrained by metal components. Due to the gap between various components, the friction and collision phenomena would occur under earthquake excitation. Dynamic response of multi-body metal internals under seismic loading is a complex nonlinear dynamical behavior, and it can be directly affected by the equivalent model and seismic excitation. In this program, we intend to design and simplify the equivalent model of multi-body structure of metal internals both experimentally and theoretically based on the nonlinear effects during collision process. The changes of stress and strain are calculated by using time history method, in order to evaluate the security and integrity and to obtain the correspondence between the excitation conditions and the dynamic response during running process. Based on the correspondence, rationally adjust and optimize the design configuration with the goal of operational safety of HTR. Then the optimal structure and the evaluation method of metal internals will be obtained. Through this research project, the evaluation criteria for running security of metal internals in HTR can be established. Furthermore, a suitable methodology for seismic research on metal internals can be established, which would provide theoretical support for the design and development of HTR.

与传统压水堆堆内构件不同，高温气冷堆堆内构件是由上万个陶瓷构件堆砌而成，并通过金属构件支撑和约束，各部件之间存在间隙，在地震激励下会出现摩擦和碰撞现象。散体金属堆内构件在地震条件下的动态响应是一复杂的非线性动力学行为，碰撞模型的等效和地震激励条件的变化将直接影响构件的动态响应。本项目拟从研究接触碰撞过程中的非线性效应出发，在此基础上采用实验测算和数值仿真相结合的方法设计及简化散体金属堆内构件的等效模型，运用时程分析法计算堆内构件应力和应变的时程变化，进而评价构件运行过程中的安全性和完整性，获得激励条件与动态响应的对应关系；在此对应关系下，以高温气冷堆的运行安全性为目标，合理调整及优化设计构型，获得散体金属堆内构件的最优结构和评价方法。通过本项目研究，可建立散体金属堆内构件运行安全性的评价准则，进而建立一套适用于散体金属堆内构件抗震研究的方法体系，为高温气冷堆的设计和研发提供理论支持。

近年来，清华大学核研院正在紧锣密鼓的往前推进高温气冷堆项目。高温气冷堆包含众多散体堆内构件，其安全性分析势在必行。压力容器和蒸汽发生器在各种工况下的应力强度、变形量、密封性和抗震性能的评价非常关键，它们与反应堆的安全性和稳定性息息相关。为了完成模块式高温气冷堆的安全评价，本项目结合ANSYS软件与ABAQUS软件，系统探讨了一系列与压力容器和蒸汽发生器相关结构的有限元分析。通过计算法兰密封环的回弹量，验证了蒸汽发生器风机壳和吸收球驱动壳的密封性符合规范要求。通过优化压力容器卸料管嘴的构型，大大提升了卸料管嘴的密封性能。利用弹性曲梁公式对球床模块式高温气冷堆堆芯壳吊耳危险截面的承压应力进行校核，结果显示，吊耳危险截面的应力小于材料的应力限值。同时采用有限元软件对该吊耳整体模型和局部模型均做了应力强度的评价，结果表明，保证堆芯壳安全竖直起吊和翻身起吊的必要条件分别是，两主吊耳的受力比例小于1.79和质心位置离支点小于堆芯壳长度的 61.2%。通过计算上支承板、下支承板和底板组件在地震工况下的响应，验证了其应力和变形均满足ASME规范要求，且安全裕度很大。分别采用接触碰撞法和弹簧连接器等效法，对蒸汽发生器传热管进行地震响应有限元分析。结果表明，弹簧连接器模型的地震响应结果与接触碰撞模型基本一致，但计算成本却得到了大幅度的提高。本项目对压力容器和蒸汽发生器的设计及实验验证提供了一定的理论支持，吊耳的应力分析为堆芯壳的安全起吊奠定了理论基础。搭建了石墨堆芯缩比模型的抗震试验台架，详细设计了抗震试验过程并仔细分析了观察到的试验现象，对模型拆除后各部件的形态进行了详细记录分析，并对模型构件的动态位移情况进行了一定深度的探讨。结果表明，模型各构件（石墨、防旋键、紧箍带等）均无明显破损，控制棒在强震下可以顺利下落。证明了HTR-PM石墨堆芯结构在地震激励下的可靠性。另外，还研究了辐照对SiC材料磁性的调控，以及轻水堆燃料包壳涂层的制备和表征。