The ASME Section XI Task Group on Fatigue in Operating Plants presents their report on metal fatigue in operating nuclear power plants in this WRC Bulletin. A review of the status of fatigue design, inspection and monitoring practices in U.S. nuclear power plants and summarizes the occurrence of fatigue related failures in plant components are included.

The document was prepared by the ASME Section XI Task Group on Fatigue in Operating Plants and other interested individuals from Structural Integrity Associates. The objectives are to review the status of fatigue design, inspection and monitoring practices in operating U.S. nuclear power plants as well as to summarize the occurrences of fatigue related failures in plant components. Failures that have occurred in operation frequently were in locations that were overlooked during design. The Task Group concludes that, while metal fatigue is not a major operating concern in nuclear power plants, there have been sufficient instances of fatigue related concerns in plants that the ASME Section XI should provide more specific guidance to address fatigue concerns in operating plants. Although providing guidance for cracks, the ASME Boiler Code provides no similar guidance for a fatigue concern. Recommendations based on the review are directed to newly identified fatigue concerns, such as those unrelated to welds, where additional work by the Task Group will result in proposed additions to the ASME Code to provide guidance for utilities to minimize fatigue related concerns.