Improvements in Article A-3000 of Appendix A for Calculation of Stress Intensity Factor in Section XI of the 2015 Edition of ASME Boiler and Pressure Vessel Code

Abstract

Analytical evaluation procedures for determining the acceptability of flaws detected during in-service inspection of nuclear power plant components are provided in Section XI of the ASME Boiler and Pressure Vessel Code. Linear elastic fracture mechanics based evaluation procedures in ASME Section XI require calculation of the stress intensity factor. Article A-3000 of Appendix A in ASME Section XI prescribes a method to calculate the stress intensity factor for a surface or subsurface flaw by making use of the flaw location stress distribution obtained in the absence of the flaw. The 2015 Edition of ASME Section XI implements a number of significant improvements in Article A-3000. Major improvements include the implementation of an alternate method for calculation of the stress intensity factor for a surface flaw that makes explicit use of the Universal Weight Function Method and does not require a polynomial fit to the actual stress distribution and the inclusion of closed-form equations for stress intensity factor influence coefficients for cylinder geometries. With the inclusion of the explicit weight function approach and the closed-form relations for influence coefficients, the procedures of Appendix A for the calculation of stress intensity factors can be used more efficiently. A review of improvements that have been implemented in Article A-3000 of Appendix A in the 2015 Edition of ASME Section XI is provided in this paper. Example calculations are provided for illustration purpose.

Progress on Grizzly Development for Reactor Pressure Vessels and Reinforced Concrete Structures

“…The function weights are determined by fitting a polynomial to the through wall stress in the RPV. FAVOR uses a 3rd order polynomial, although recently developed SIFICs [11,12] are based on the use of a 4th order polynomial to obtain a more accurate representation. The ASME Boiler & Pressure Vessel Code [13] provides closed-form expressions and tabular data for SIFICs for a variety of circumferential and axial elliptical and semi-elliptical flaws in thick-walled cylinders and plates in Section XI, Article A-3000.…”