consists of two major tasks: (1) the development. of fracture mechanics models for assessing the piping reliability in light water reactor plants; and (2) the validation of the models developed in task (1) by comparing the results with real piping failure data observed. The results of task (2) impact the confidence level for the models developed in task (1). This report is only concerned with task (1). Task (2) results are reported in another NUREG report, 11 Piping Reliability Model Validation and Potential Use for Licensing Regulation Development ... The ultimate objective of this pnoject is to provide guidance for nuclear powe.r plant piping design so that high-reliability piping systems can result. The piping reliability model presented in this report covers two major failure modes, namely, fatigue failure ~nd stress corrosion cracking failure. Both have been observed in the piping systems of light water reactor plants~ Various failure mechanisms such as vibratory stresses, residual stresses, seismic stresses, assembly stresses, and operating stresses, attributed to these two failure modes are considered in the model. Initial interior surface flaws are assumed to exist along either the pipe circumferential direction or the longitudinal direction. In-service inspection is also included in the model. In summary_,. this piping reliability model has wide application to piping 5y5tems in nuclea~ powet• plants .
Approximate influence functions are presented for a part-circumferential semielliptical interior surface crack in a circular pipe. The influence functions are derived from the crack surface opening displacements obtained by the use of boundary integral equation techniques. Such functions are useful in evaluating stress-intensity factors for cracks in bodies subjected to complex stress conditions, and convenient curve fits suitable for numerical calculations are provided. The stress intensities are obtainable for arbitrary stresses by numerical integration techniques. Comparisons with existing solutions indicate that the influence functions provide results of suitable accuracy for engineering purposes. The results indicate that the stress-intensity factor is not strongly dependent on the parameter Ri/h or on whether the crack is longitudinal or circumferential. Details of the variation of K along the crack front are not obtainable from the influence functions, only “root-mean-square (RMS)-averaged” values are generated. However, such values are useful in the analysis of the growth of semielliptical cracks, and the results presented should be of wide use in the analysis of such cracks under complex stress conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.