Examples of high cycle thermal fatigue (HCTF) damage cases onPWR austenitic stainless steel components are reported. High cyclethermal fatigue risk is primarily due to mixing of cold and hot water,unexpected leaks of cold water through check valves or to turbulentpenetration of hot water running in a main pipe into a connected line.When such thermal fatigue issues are identified in PWR powerplants, manufacturing improvement such as inner surface polishingof austenitic stainless steel parts can be performed to increase thefatigue resistance of the components.