This paper presents a finite element analysis (FEA) based approach to perform crack growth evaluation of remnant cracks in a mockup with a partial arc excavate and weld repair (EWR). The partial arc EWR is a mitigation option to address stress corrosion cracking (SCC) in nuclear power plant piping systems. The mockup is a dissimilar metal weld (DMW) consisting of an SA-508 Class 3 low alloy steel forging buttered with Alloy 182 welded to a Type 316L stainless steel plate with Alloy 82/182 weld metal. This material configuration represents a typical DMW of original construction in a pressurized water reactor (PWR). To create a representative partial arc EWR application, the outer half of the DMW is excavated and repaired with Alloy 52M weld metal. The crack growth evaluation process presented herein represents an advanced method to evaluate the Alloy 82/182 remnant crack growth as required by ASME Code Case N-847 for implementing a partial arc EWR, which is currently being considered via letter ballot at ASME BPV Standards Committee XI. After the repair, any crack that remains in the Alloy 82/182 remnant and underneath the EWR needs to be evaluated for stress corrosion cracking (SCC) to assess its potential to grow beyond the EWR coverage area. Conventional fracture mechanics approach may not be suitable to evaluate such a remnant crack because of its close proximity to multiple materials of different mechanical properties and unconventional crack shape. In the crack growth evaluation, a crack that is reminiscent of a circumferential crack in a pipe, and a crack that is reminiscent of a laminar crack in a pipe are evaluated to predict the time for each of them to grow beyond the partial arc EWR coverage arc length. It is expected that the approach, analysis steps, calculation procedures presented in this paper will be applicable to analyzing a pipe geometry using realistic residual stresses and operating stresses for an EWR.

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