27 ASME Section XI Developments in Evaluation Procedures for Nuclear Piping Degraded by Flaws and Corrosion Processes in Response to Lessons Learned

This chapter summarizes past and ongoing developments in flaw Acceptance Standards and analytical evaluation procedures in Section XI of the ASME B&PV Code for nuclear piping degraded by flaws and corrosion processes that are in response to industry needs and lessons learned. A significant number of revisions have been made to address intergranular stress corrosion cracking in Boiling Water Reactor Class 1 austenitic piping, and primary water stress corrosion cracking in Alloys 82, 182, and 132 dissimilar metal welds in piping in Pressurized Water Reactors. More recent revisions to Section XI, as well as developments that are under review in Section XI, to address stress corrosion cracking are described in this chapter. A major revision to the flaw Acceptance Standards was to prohibit application to planar surface flaws that are detected in piping materials that are susceptible to stress corrosion cracking and are in contact with reactor coolant environments.