Optimization of steam generator performance

Corrosion related steam generator problems have occurred in various countries. The operating experience from steam generators constructed after the KWU concept has been excellent. Incoloy 800 has been exclusively used as tube material. In these steam generators, design such as fulldepth expansion of the U-tubes into the tubesheet and austenitic stainless steel tube spacers have avoided problems such as crevice corrosion and denting. A high pH value minimizes the ingress of impurities and corrosion products into the steam generators, thus eliminating the risk of pitting and caustic corrosion. Service machines such as robots were developed to improve tube inspection, maintenace and repair, aimed at the reduction of dead time and radiation exposure. One of the most important maintenance techniques is periodic cleaning by tubesheet lancing or by chemical cleaning of the bundle. (orig.)