The existence of a complex-crack in the US nuclear plant fleet was first discovered at the Duane Arnold BWR plant where large circumferential IGSCC cracks were found in several safe ends. In order to characterize the fracture behavior of these complex-cracks, several research projects were conducted which included full-scale pipe tests. Since then, little work has been conducted on this topic until recently. The occurrence of PWSCC in PWR plants raised the concern that a complex-crack could develop in dissimilar metal welds under certain conditions. This was demonstrated by using a detailed 3D finite element analyses that allowed a natural PWSCC crack growth. Thus, there is a need to further investigate the fracture behavior of a complex-crack in a pipe.

In this paper, lessons learned from the past complex-cracked pipe tests are summarized first. Then, based on the findings from the past work, a novel complex-cracked fracture specimen was proposed to characterize a complex-crack in a pipe. The typical C(T) and SEN(T) specimens were modified by inserting an additional notch only on one side of the specimen. These specimens were used to analyze the past complex-cracked pipe tests. The experimental results obtained from the modified SEN(T) specimen, namely complex-cracked tension [CC(T)-2] specimen, were able to reproduce the complex-crack fracture behavior observed in past pipe tests.

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