BLOCK MONITORING METHOD OF SG TUBE SUPPORT PLATE WITH INTELLIGENT ECT FOR MAINTENANCE WORK

摘要

Intelligent ECT (Eddy Current Testing) probe (I-Probe) has a capability to inspect tubes more productively and more accurately than conventional probes for Steam Generators (SG) as shown in Fig. 1. And I-Probe provides effective "One-Pass" solution by combination with MHI (Mitsubishi Heavy Industries, Ltd.) Intelligent Data Analysis System (MIDAS). It has been applied to full length tube inspection in Japan since 2003 and there is much field experience to date. On the other hand, a phenomenon in SG secondary side is known that scale deposits clog holes of quatrefoil type tube support plate (TSP). Water level oscillation of secondary side caused by excessive blockage of scale deposits may decrease operation efficiency and it can be a cause of unintended troubles. Therefore, periodical monitoring of blockage condition and applying countermeasures like secondary side cleaning are very important. A new method has been developed to evaluate blockage condition of every TSP around all tubes automatically using I-Probe data. Also, a new software has been developed to visualize the evaluation results as color maps. This new method may contribute to increase the reliability of SG maintenance like cleaning, because the new method makes it possible to monitor a whole SG condition more precisely.