Welding Residual Stress in a Large Diameter Nuclear Reactor Pressure Vessel Nozzle

The Atucha II nuclear power plant is a pressurized heavy water reactor being constructed in Argentina. The original plant was designed by KWU in the 1970’s using the German methodology of break preclusion. The plant construction was halted for several decades, but a recent need for power was the driver for restarting the construction. Many times welding residual stresses in nuclear power plant can lead to cracking concerns. Hence, understanding the residual stress distribution is important to evaluate the reliability of pipe and nozzle joints with welds.In this paper, a large diameter Reactor Pressure Vessel (RPV) hot-leg nozzle was analyzed. This is a nozzle from Atucha II nuclear power plant in Argentina. The main weld material is 20MnMoNi55 and ID welded cladding is made of 309L. The special materials and weld geometry will lead to interesting welding residual stress field. In addition, post-weld heat treatment (PWHT) region and boundary conditions could also play an important role in determining welding residual stress fields. Sensitivity analyses were conducted and the technical observation and comments will conclude the paper.Copyright © 2012 by ASME