Thermal, Hydraulic, and Corrosion Aspects of PWR Steam Generator Problems

Abstract

Two types of PWR steam generators are in use: recirculating steam generators (RSGs) and once-through steam generators (OTSGs). Most of the units and vertical and this review will be limited to vertical units. Some of these steam generators have operated with a minimum of problems while other steam generator designs have experienced a variety of corrosion and mechanically induced problems. The discussion will focus more on the designs that have experienced problems and the effort expended to correct them. Corrosion problems include denting, wastage, intergranular attack, stress corrosion cracking, corrosion fatigue, pitting on the outside surfaces of the tubes, and stress corrosion cracking the inner surfaces of the tubes. Mechanical concerns have included water hammer, thermal stratification in feed-water pipes, fretting and wear of the tubes caused by excessive tube vibration, and erosion-corrosion. These problems have caused unscheduled outages and expensive repairs.