Session: MF-03-01 Weld Residual Stress and Distortion

Paper Number: 125081

125081 - Full Scale Three-Dimensional Moving Arc Weld Analyses of Control Rod Drive Mechanism J-Groove Welds and Implications on Cracking 

Flaw indications have been found in some nozzle to stainless steel piping dissimilar metal (DM) welds and reactor pressure vessel heads (RPVH) in pressurized water reactors (PWR) throughout the world. The nozzle and J-groove welds usually involve welding ferritic (often A508) nozzles using Alloy 182/82 weld metal. The welds may become susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually >300C) and the water chemistry in the PWR is typical of operating plants. The weld residual stresses (WRS) induced by the welds are a main driver of PWSCC. Crack growth in the J-groove welds of the vessel heads remains a major concern for the integrity of the heads.

Computational weld analyses were performed for nozzles of different angles including 0-degree (top dead center), 25-degree, and 53-degree nozzles. In the past simplified weld analyses of the J-groove welds using a ‘lump pass’ analysis procedure and simple geometric symmetry assumptions of the welds.  Here full moving arc solutions of the full J-groove welds are made without the simplified geometric assumptions made in the past.  Here FE models were used in this project to perform analyses of a 25-degree and a 53-degree nozzle and compared to WRS measurements as several locations in head nozzles. Comparisons between full moving arc solutions with the prior lump pass solutions were made indicating that the lump pass solutions produce incorrect results for some J-groove welds.

This paper summarizes WRS fields that are developed in the J-groove welds and ramifications on crack growth in the welds.  An example of crack growth in these WRS fields is also shown.

Presenting Author: Frederick (bud) Brust Engineering Mechanics Corporation of Columbus

Presenting Author Biography: F. W. (Bud Brust) works at Engineering Mechanics Corporation of Columbus (EMC2).

Authors:

Frederick (bud) Brust Engineering Mechanics Corporation of Columbus
Ed Punch Engineering Mechanics Corporation of Columbus
Elizabeth Twombly Engineering Mechanics Corporation of Columbus