Advanced Finite Element Analysis (AFEA) Evaluation for Circumferential and Axial PWSCC Defects

Abstract

The Advanced Finite Element Analysis (AFEA) methodology has been developed by the US NRC and the nuclear industry to evaluate the natural crack growth of primary water stress corrosion cracking (PWSCC) in nickel-based alloy materials. The AFEA methodology allows the progression of a planar crack subjected to typical SCC-type growth laws by calculating stress intensity factors at every nodal point along the crack front, and incrementally advancing the crack front in a more natural manner. This paper describes the enhancements that have been made to the existing AFEA methodology. The most significant enhancement was the feature to evaluate axial crack growth where the crack was contained within the susceptible material. In this paper, this methodology was validated by performing an AFEA evaluation for the axial crack that was found in the V.C. Summer hot leg dissimilar metal weld. Other enhancements to the AFEA methodology include; upgrade to the PipeFracCAE© software developed by Engineering Mechanics Corporation of Columbus, feature to handle non-idealized circumferential through-wall cracks, mapping of weld residual stress for crack growth, and determination of limiting crack size using elastic-plastic J-integral analysis that included secondary stress (weld residual stress and thermal transient stress) effects.

The Huge Missing Factor in Leak-Before-Break Analysis: How a Circumferential Through-Wall-Crack in a Pipe System Changes the Flexibility and Reduces the Applied Moments

“…In doing so, an iterative FE analysis was conducted with the worst-case SCC crack growth rate observed in any nuclear plant (even though those materials were not used in the Argentina plant). The iterative FE approach crack shape modelling and some validations are described in detail in References [Shim et al 2012 andShim et al 2010]. The high crack growth rate was used since the design was for 80 years of life.…”

Determination of residual stresses in welded components by finite element analysis

“…The standard of validation required depends on the sensitivity of subsequent structural integrity assessments to the presence of residual stress. Thus, high levels of validation may be required for assessments of safety-critical plant with the potential for brittle fast fracture, or where stress corrosion cracking is a concern (for example, see 30,47,[55][56][57][58][59] ). Three validation standards are defined:…”