A new feedwater control/isolation scheme to reduce steam generator thermal transients

Con Edison has recently implemented a design modification for its Indian Point 2 (IP2) Westinghouse four-loop pressurized water reactor that delays feedwater isolation following a reactor trip and low T average. The purpose of the change is to reduce thermal transients to the steam generators by maintaining a flow of relatively hot main feedwater, rather than only cold auxiliary feedwater, until the steam generator levels recover. The goal is to reduce thermal stresses in the steam generator girth weld region. An additional benefit is reduction of thermal stresses to other components such as the feedwater nozzles. Based on engineering, operations, and safety considerations, this method was chosen over other potential solutions such as heating the auxiliary feedwater before it enters the steam generators. The project utilized a multidisciplinary approach and involved extensive design and analysis, testing, and operator training on the IP2 simulator