反应堆压力容器下封头内表面缺陷涡流检验技术研究及应用

Research and Application of Eddy Current Testing Technology for Defects on the Lower Head Surface of the Reactor Pressure Vessel

摘要: 反应堆压力容器是核电厂的关键核安全一级设备，其下封头内表面承受复杂工况环境和外来异物打击，容易形成凹坑和危害性缺陷。针对反应堆压力容器下封头堆焊层磨损区的缺陷检测难题，本文研究了一种基于弹性点式平面线圈探头的涡流检验方法。该方法采用弹簧支撑的单点式平面线圈探头设计，通过弹性机构实现探头与缺陷表面的充分耦合，有效减少提离效应对检测信号的影响。通过涡流渗透深度与激励频率的理论关系，优化设计了300 kHz主频涡流检测系统。工程应用表明，该技术能有效检出某核电站反应堆压力容器下封头内表面缺陷，为核电站压力容器在役检查提供了可靠的技术手段。

Abstract: The reactor pressure vessel is critical nuclear safety Class I equipment in nuclear power plants. Its lower head inner surface is subjected to complex operating environments and impacts from foreign objects, making it prone to forming pits and hazardous defects. To address the challenge of defect detection in the surfacing layer of the reactor pressure vessel lower head, this paper investigates an eddy current testing method based on an elastic point-type planar coil probe. The method employs a spring-supported single-point planar coil probe design, which achieves sufficient coupling between the probe and the defective surface through an elastic mechanism, effectively reducing the influence of the lift-off effect on the detection signal. Based on the theoretical relationship between eddy current penetration depth and excitation frequency, an eddy current testing system with a main frequency of 300 kHz was optimally designed. Engineering applications demonstrate that this technology can effectively detect defects on the inner surface of the lower head of a nuclear power plant’s reactor pressure vessel, providing a reliable technical means for the in-service inspection of nuclear power plant pressure vessels.