Session: CS-14-01: Repair, Replacement and Mitigation for Fitness-for-Service Rules

Paper Number: 83798

83798 - Revision of Case N-666-1 to Permit Overlay Repair of Dissimilar Metal Socket Welds and to Allow Higher Carbon Content in the Pipe and Socket Fitting 

ASME Section XI Case N-666, Weld Overlay of Class 1, 2, and 3 Socket Welded Connections, was developed for weld overlay repair of non-isolable leaking socket welds where the mode of failure is determined to be fatigue cracking attributed to mechanical vibration. The case was approved by ASME on April 18, 2006 and first published in Code Case Supplement 9 to the 2004 Edition of ASME Section XI.

Case N-666 and N-666-1 have served the industry well, allowing repair of leaking socket welds where the system cannot be readily drained and isolated for cutout and full pipe replacement. This has provided significant benefit to the nuclear industry by allowing the repair to be performed on-line without the need to shut the plant down, avoiding significant loss in power generation.

This paper provides the technical basis for proposed changes to Case N-666-1 that will expand the scope of socket welds that can be repair by weld overlay. The revision will expand the case to include overlay repair of dissimilar metal socket welded joints.  The revision will also remove the 0.30 wt% maximum carbon content limitation when the overlay repair is installed with water backing.  Finally, the revision will also address the conditions imposed by the NRC in Regulatory Guide 1.147 Revision 19.

Presenting Author: Steven McCracken EPRI

Presenting Author Biography: Work Experience: - Steve has worked in the nuclear industry for over 44 years and is a registered Professional Engineer in the state of Missouri. - Steve has worked for EPRI since May 2007 and is currently a Technical Executive in the Welding & Repair Technology Center located in Charlotte, North Carolina. - Prior to EPRI Steve was a Consulting Welding Engineer and ASME R&R Engineer at the Callaway Nuclear plant in Missouri. - Before his Engineering career Steve was a certified pipe-fitter welder and worked at Callaway and Wolf Creek nuclear power plants during construction. - Steve is active in the ASME Codes and works in the area of materials, welding, and repair/replacement activities. Education: - BS in Mechanical Engineering from the University of Missouri, USA - MS in Welding Engineering from The Ohio State University, USA

Authors:

Steven McCracken EPRI
Christopher Lohse Gateway for Accelerated Innovation in Nuclear (GAIN)