Welding residual stress analysis for weld overlay on a BWR feedwater nozzle

摘要

This paper is to perform the welding residual stress analysis for weld overlay on a dissimilar metal weld of feedwater nozzle at a Taiwan domestic boiling water reactor. To mitigate the degradation of nozzle weld, a weld overlay repair was implemented for assuring its structural integrity. Based upon ASME Code Case N-504, the weld overlay repair has to be analyzed to improve residual stress at the inside surface of original weld. Using ANSYS finite element analysis software, an axis-symmetric model is specifically developed for the feedwater nozzle in this work. Field welding procedures and detailed welding simulations are both taken into account to predict welding residual stress during weld overlay repair. The residual compressive stress can thus be obtained at the inside surface of original weld. The present numerical models are also compared with those in the public technical reports to show their accuracy. The computed welding compressive stress would be helpful for the resistance of degraded feedwater nozzle with overlay to stress corrosion cracking and further crack growth during subsequent operation.