This paper discusses the comprehensive integrity assessment of feeders fabricated from normalized pipe and elbow piping items subject to Flow Accelerated Corrosion (FAC) during in-service conditions. The arguments are based on the improved mechanistic understanding of FAC; review of international piping rupture events; examinations of removed feeders; burst-pressure tests of prototypical and ex-service feeder piping sections, the minimum acceptable wall thickness for feeder piping; and station feeder life cycle management plans. It is concluded that rupture of feeder pipe due to FAC is a very low probability event.

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Aging steam generator tubes have been experiencing a variety of degradations such as pitting, fretting wear, erosion-corrosion, thinning, cracking, and denting. To assist with steam generator life cycle management, some defect-specific flaw models have been developed from burst pressure testing results. In this work, an alternative approach; heterogeneous finite element model (HFEM), is explored. The HFEM is first validated by comparing the predicted failure modes and failure pressure with experimental measurements of several tubes. Several issues related to the finite element analyses such as temporal convergence, mesh size effect, and the determination of critical failure parameters are detailed. The HFEM is then applied to predict the failure pressure for use in a fitness-for-service condition monitoring assessment of one removed steam generator tube. HFEM not only calculates the correct failure pressure for a variety of defects, but also predicts the correct change of failure mode. The Taguchi experimental design method is also applied to prioritize the flaw dimensions that affect the integrity of degraded steam generator tubes such as the defect length, depth, and width. It has been shown that the defect depth is the dominant parameter controlling the failure pressure. The failure pressure varies almost linearly with defect depth when the defect length is greater than two times the tube diameter. An axial slot specific flaw model is finally developed.

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