稳压器电加热元件泄漏分析和检测方案设计

Leak Problem Analysis and Detection Plan for Pressurizer Electric Heater

稳压器电加热元件包壳破损吸湿肿胀引起的开裂事故在国内外均有发生,这种事故均与电加热元件包壳存在泄漏有关。国内某核电项目热试期间发现部分电加热元件绝缘性能不符合设计要求,通过检测,发现与密封性相关的焊缝存在泄漏缺陷。为避免严重的由于泄漏引起的电加热元件肿胀开裂事故,对出现绝缘降质的电加热元件进行了详细的检查和分析。分析表明单纯进行表面检测是有风险的。为了保证电加热元件的密封性能,除了对包壳管材料进行氦检漏,端塞-包壳焊缝也需要进行氦检漏。结合电加热元件的结构和制造工艺特点,设计了专用的检测系统,并设计了一套完整检测方案。至此,稳压器电加热元件的密封完整性得到了全面的检测,排除了泄漏隐患。

Electric heater is one of the important functional unit~ of the pressurizer, and the electric heater sheath broken happened both in China and other countries. The broken is usually associated with leak. Leak will result in water penetration and electric heater will swell, thus the mechanical failure happens. It will cause the leak of the primary coolant circuit. A faulty insulation problem had been found during the hot functional test in a nuclear power project, and the leak flaw was found by test and analysis. In order to avoid the sheath broken, analysis and test have to be conducted to solve the problem. Researches show that only PT at welding is not enough, and it is risky. LT （He） is both important and RT is also needed at welding part. A new plan of none destructive test has been proposed. It will be favorable for the sealing performance of the pressurizer electric heater.