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

Paper Number: 85151

85151 - Development of the Technical Basis for the New Code Case “Performance and Qualification Criteria for Mitigation of Stress Corrosion Cracking by Surface Stress Improvement” 

Stress corrosion cracking (SCC) of nuclear power plant components is a concern when designing new components or making repairs to material potentially susceptible to SCC.  Actions were taken within ASME Section III Task Group Weld Residual Stress to ensure mitigative actions (e.g., surface stress improvement) are taken when a repair is done on wetted surface of a component susceptible to SCC. The intent is to minimize in service stress corrosion cracking by mitigating during construction. However, the performance criteria for applying surface stress improvement such that the repaired area can be considered mitigated was not available for users of ASME Section III. A code case is needed to provide performance criteria for Section III applications and additional testing was undertaken to support the case.

Several organizations including DOOSAN and the Welding and Repair Technology Center (WRTC) and Advanced Nuclear Technology (ANT) programs of the Electric Power Research Institute (EPRI) jointly executed a three-year test program focused on evaluating the viability of novel to nuclear surface stress improvement techniques such as Ultrasonic Nanocrystal Surface Modification (UNSM) and Low Plasticity Burnishing (LPB) techniques. The program also included further demonstration of laser peening (LP) processes as a complement to the LP test data already captured by prior EPRI Materials Reliability Program (MRP) work (i.e., MRP-267 R2). This paper summarizes the results from the DOOSAN-WRTC-ANT test program that supports the SSI performance criteria for mitigation of SCC of ASME Section III components.

 

Presenting Author: Nicholas Mohr EPRI

Presenting Author Biography: Nick has a B.S. in Welding Engineering from The Ohio State University with a minor in Nuclear Engineering, Master of Engineering and Master of Business Administration from North Carolina State University. He is a registered Professional Engineer in the states of North and South Carolina. Nick started his career in 2005 working for Duke Energy as the nuclear Corporate Welding Engineer until 2012. He then worked at Structural Integrity Associates, Inc. as a consulting welding engineer until his arrival to Electric Power Research Institute (EPRI) Welding Repair and Technology Center (WRTC) in 2015. At EPRI he continued working with welding programs, assessments, and associated training in addition to research spanning from surface stress improvement techniques to various natural language processing projects.

Authors:

Nicholas Mohr EPRI
Stephen Tate EPRI
Marc Albert EPRI
Sungwoo Cho Doosan Heavy Industries & Construction
Won-Geun Yi Doosan Heavy Industries & Construction
Jean Collin Dominion Engineering, Inc.
Markus Burkardt Dominion Engineering, Inc.
John Broussard Dominion Engineering, Inc.
Young Sik Pyun Sun Moon University