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