某核电机组疏冷器失效原因分析及改进措施

Analysis on Failure Reasons and Improvement Measures of the Drain Coolerin a Nuclear Power Unit

某核电机组常规岛热力系统设置外置式疏冷器,机组首次大修时发现疏冷器部分换热管及栅架板断裂、部分换热管存在磨损及泄漏现象。断口形貌显示换热管及栅架板为振动损坏。应用换热器相关的国内外准则进行分析,明确该疏冷器换热管损坏的根本原因为壳程凝结水流速过快,流体弹性失稳、旋涡脱落诱发管束振动,造成尾部换热管及栅架损坏。针对这种状况,采取控制流速、加装防振栅架等措施,确保不会发生流致振动问题,从而保证疏冷器安全运行。

An external drain cooler is introduced into the thermal system for the conventional island of a nuclear power unit.It is found that some heat exchange tubes are fractured,some grille plates are broken,and some heat exchange tubes are worn and leaking of the external drain cooler when the unit is overhauled.The fracture morphology shows that the heat exchange tubes and the grille plates are damaged by vibration.The criteria of heat exchange at home and abroad are used for analysis in this paper,it is determined that the root reason for the damage of the heat exchange tubes is that the condensation water velocity in the shell side is too fast,the fluid elasticity is unstable,and the vortex separation induces the vibration of the tube bundle,damage to the heat exchange tubes and the grille plates at the U-bend.In view of this situation,measures are taken to control the flow rate and install anti vibration grille plates.Ensure that no flow induced vibration problems occur,so as to ensure the safe operation of drain cooler.