真空环境下燃料组件压紧弹簧疲劳应力松弛研究

Study on Fatigue Stress Relaxation of Compression Spring for Fuel Assembly in Vacuum

反应堆燃料组件压紧弹簧需要长期在高温和压应力下服役,其材料的正确选型对燃料组件的设计具有重要意义。针对反应堆运行过程中可能因机械振动和流致振动等引起的压紧弹簧疲劳破坏现象,本文对三种备选奥氏体不锈钢压紧弹簧(GH 2132、632和GH4169)在450℃条件下进行了10万次疲劳循环的真空疲劳试验。试验结果表明:所有弹簧均保持形态完整,没有出现断裂失效现象。GH4169弹簧在试验后没有发现明显的析出物。同时其处于低层错能状态,位错运动形式更多的是单滑移,变形过程中塑性的累积困难,表现出较好的抗应力松弛性能。最终优选GH4169作为反应堆组件压紧弹簧备选材料,为反应堆燃料组件设计与制造提供一定参考。

Fuel assembly compression spring in reactors need performance condition under high temperature and pressure for a long period.The correct selection of springs has great significance to the design of fuel assemblies.Aiming at the fatigue failure problems,such as mechanical vibration and induced vibration,three kinds of austenitic stainless-steel compression springs(GH 2132,632 and GH4169)tests in vacuum with 100,000 cycles were carried out at 450℃.The results showed that all the springs were in complete shape and no fracture failure occurs.No obvious precipitates were found in GH4169 spring after fatigue test in vacuum and the type of dislocation slip dominated by planar slip because of the low stacking fault energy state.It is difficult to accumulate plasticity in the process of deformation,which shows better stress relaxation resistance.Finally,GH4169 was selected as an alternative material for the compression spring of the reactor assembly,which provides a reference for the design and manufacture of the reactor fuel assembly.