Seminar: The Use of Weld Overlay Technology to Extend the Lifetime of Commercial Nuclear Reactors

Abstract:

Weld overlay technology has been widely used in the nuclear power industry to extend the lifetime and insure the safety of operating reactors.  The motivation for the use of weld overlay was largely driven by the discovery that primary water stress corrosion cracking (PWSCC) was compromising the integrity of critical reactor components constructed from INCONEL Alloy 600 or transition joints made with INCONEL 82 filler metal. Unbeknownst at the time of construction, the low chromium content of these materials led to degradation by PWSCC after extended service exposure.  The mitigation strategy used in the nuclear power industry is to simply replace components with higher chromium alloys, such as INCONEL Alloy 690, or to overlay the susceptible regions with a high chromium, Ni-base filler metal. The latter strategy has been adopted worldwide to restore the integrity of “safe end” welds that connect the reactor pressure vessel to stainless steel piping.  This presentation will discuss the weld overlay strategy that has been successfully implemented at many power plants. The selection of materials and some of the weldability issues that have been encountered will also be discussed.

About the Speaker:

Dr. Lippold is a Professor in the Welding Engineering Program and Head of the Welding and Joining Metallurgy Group at The Ohio State University. He is also a College of Engineering Distinguished Faculty at OSU.  He received his B.S., M.S. and Ph.D. degrees in Materials Engineering from Rensselaer Polytechnic Institute where he was a student of Dr. Warren F. Savage.  Upon completion of his formal education, he worked for seven years at Sandia National Laboratories, Livermore, CA as a member of the technical staff, specializing in the area of stainless steel and high alloy weldability. From 1985 to 1995, Dr. Lippold worked for Edison Welding Institute.  In 1995, he joined the faculty of the Welding Engineering Program at OSU. Over the past 35 years, Dr. Lippold has been involved in research activities designed to gain a better understanding of the welding metallurgy and properties of engineering materials.  He has been actively involved in the evaluation of weldability test techniques and the development of testing approaches that provide useful engineering information.  Based on this research, Dr. Lippold has published over 300 technical papers and reports. He is recognized internationally in the field of stainless steel and high alloy welding metallurgy, and weldability testing.  Since joining OSU in 1995 he has advised over 60 graduate students.  He has published three textbooks, Welding Metallurgy and Weldability of Stainless Steels (2005), Welding Metallurgy and Weldability of Nickel-base Alloys (2009), and Welding Metallurgy and Weldability (2014).  Dr. Lippold is a Fellow of both ASM International (1994) and the American Welding Society (1996). He is currently co-editor of the international journal Welding in the World published by IIW.