An Analytical Evaluation of the Effect of Weld Material Thickness on Residual Stresses Produced by Structural Weld Overlays on Pressurized Water Reactor Primary Cooling Piping

2009 ◽  
Author(s):  
L. F. Fredette ◽  
Paul M. Scott ◽  
F. W. Brust ◽  
A. Csontos
Keyword(s):  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Intergranular Stress Corrosion ◽  
Pressurized Water ◽  
Weld Overlay ◽  
Water Reactor ◽  
Dissimilar Metal ◽  
Structural Reinforcement

Full Structural Weld Overlay (FSWOL) has been used successfully to mitigate intergranular stress corrosion cracking in boiling water reactor (BWR) welded stainless steel piping for many years. The FSWOL technique adds structural reinforcement, can add crack resistant material, and can create compressive residual stresses at the inside surface of the welded joint which reduces the possibility of further stress corrosion cracking. Recently, the FSWOL has been applied as a preemptive measure to prevent primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWR) on susceptible welded pipes with dissimilar metal welds common to PWR primary cooling piping. This study uses finite element models to evaluate the likely residual and operating stress profiles remaining after FSWOL and describes the results of sensitivity studies which were performed to examine the effect of weld overlay thickness on the residual stresses for typical dissimilar metal weld configurations.

An Analytical Evaluation of the Effect of Weld Sequencing on Residual Stresses Produced by Full Structural Weld Overlays on Pressurized Water Reactor Primary Cooling Piping

2009 ◽  
Author(s):  
L. F. Fredette ◽  
Paul M. Scott ◽  
F. W. Brust ◽  
A. Csontos
Keyword(s):  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Cooling System ◽  
Corrosion Cracking ◽  
Intergranular Stress Corrosion ◽  
Pressurized Water ◽  
Water Reactor ◽  
Dissimilar Metal ◽  
Structural Reinforcement

Full Structural Weld Overlay (FSWOL) has been used successfully to mitigate intergranular stress corrosion cracking in boiling water reactor (BWR) welded stainless steel piping for many years. The FSWOL technique adds structural reinforcement, can add crack resistant material, and can create compressive residual stresses at the inside surface of the welded joint which reduces the possibility of further stress corrosion cracking. Recently, the FSWOL has been applied as a preemptive measure to prevent primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWR) on susceptible welded pipes with dissimilar metal welds common to PWR primary cooling piping. This study uses finite element models to evaluate the likely residual and operating stress profiles remaining after FSWOL for typical dissimilar metal weld configurations and describes the results of sensitivity studies which were performed to examine the effect of weld sequencing on the residual stresses produced in common configurations of PWR primary cooling system piping.

Effects of Weld Overlays on Leak-Before-Break Margins

2011 ◽  
Author(s):  
G. Angah Miessi ◽  
Peter C. Riccardella ◽  
Peihua Jing
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Operating Conditions ◽  
Intergranular Stress Corrosion ◽  
Pressurized Water ◽  
Weld Overlay ◽  
Water Reactors ◽  
Weld Overlays ◽  
Leak Before Break

Weld overlays have been used to remedy intergranular stress corrosion cracking (IGSCC) in boiling water reactors (BWRs) since the 1980s. Overlays have also been applied in the last few years in pressurized water reactors (PWRs) where primary water stress corrosion cracking (PWSCC) has developed. The weld overlay provides a structural reinforcement with SCC resistant material and favorable residual stresses at the ID of the overlaid component. Leak-before-break (LBB) had been applied to several piping systems in PWRs prior to recognizing the PWSCC susceptibility of Alloy 82/182 welds. The application of the weld overlay changes the geometric configuration of the component and as such, the original LBB evaluation is updated to reflect the new configuration at the susceptible weld. This paper describes a generic leak-before-break (LBB) analysis program which demonstrates that the application of weld overlays always improves LBB margins, relative to un-overlaid, PWSCC susceptible welds when all the other parameters or variables of the analyses (loads, geometry, operating conditions, analysis method, etc…) are kept equal. Analyses are performed using LBB methodology previously approved by the US NRC for weld overlaid components. The analyses are performed for a range of nozzle sizes (from 6″ to 34″) spanning the nominal pipe sizes to which LBB has been commonly applied, using associated representative loads and operating conditions. The analyses are performed for both overlaid and un-overlaid configurations of the same nozzles, and using both fatigue and PWSCC crack morphologies in the leakage rate calculations and the LBB margins are compared to show the benefit of the weld overlays.

Preemptive Weld Overlays to Mitigate PWSCC Concerns in PWR Piping System Dissimilar Metal Butt Welds

2005 ◽  
Author(s):  
Peter C. Riccardella ◽  
Marcos L. Herrera ◽  
Arthur F. Deardorff ◽  
Shu S. Tang ◽  
Anthony J. Giannuzzi
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Piping System ◽  
Primary System ◽  
Pressurized Water ◽  
Butt Welds ◽  
Dissimilar Metal ◽  
Structural Reinforcement ◽  
Weld Overlays

Primary water stress corrosion cracking (PWSCC) continues to be a concern in nickel-based alloys (Alloy 600 and the associated weld metals, Alloys 82 and 182) in pressurized water reactors (PWRs). It has caused cracking and leakage in a number of components, including steam generator tubes, vessel head penetrations, and most recently, the dissimilar metal butt welds (DMWs) commonly used to connect vessel nozzles to PWR primary system piping. Weld overlays (WOLs) have been used extensively in the past twenty years to repair nuclear plant piping that has been found to be cracked or leaking due to stress corrosion cracking [1]. This paper summarizes the advantages of and technical justification for applying preemptive weld overlays (PWOLs) before cracking or leakage is observed, to mitigate PWSCC in Alloy 82/182 butt welds. PWOL design is governed by a number of considerations. The PWOL must supply sufficient thickness of resistant material (Alloy 52 weld metal) to provide new structural reinforcement of the original pipe weld sufficient to sustain design basis loads within ASME Code margins. Structural reinforcement calculations are presented demonstrating the achievement of this capability in accordance with ASME Section XI rules for evaluation of flaws in austenitic piping. The PWOL must supply sufficient thickness to effectively reverse the highly tensile residual stresses from the original DMW, including the potential detrimental effects of an in-process repair weld. Residual stress evaluations using elastic-plastic finite element models are presented that demonstrate the achievement of this objective for several typical nozzle geometries. Finally, analyses are presented to demonstrate that a dissimilar metal weld, with PWOL applied, meets the Nuclear Regulatory Commission (NRC) criteria for leak-before-break (LBB).

An Analytical Evaluation of the Full Structural Weld Overlay as a Stress Improving Mitigation Strategy to Prevent Primary Water Stress Corrosion Cracking in Pressurized Water Reactor Piping

2009 ◽  
Author(s):  
L. F. Fredette ◽  
Paul M. Scott ◽  
F. W. Brust ◽  
A. Csontos
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Pressurized Water ◽  
Weld Overlay ◽  
Dissimilar Metal ◽  
Before And After ◽  
Primary Water ◽  
Water Reactors ◽  
Metal Weld

Full Structural Weld Overlay (FSWOL) has been used successfully to mitigate intergranular stress corrosion cracking in boiling water reactor (BWR) welded stainless steel piping for many years. The FSWOL technique adds structural reinforcement, can add crack resistant material, and can create compressive residual stresses at the inside surface of the welded joint which reduces the possibility of further stress corrosion cracking. Recently, the FSWOL has been applied as a preemptive measure to prevent primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWR) on susceptible welded pipes with dissimilar metal welds common to PWR primary cooling piping. This study uses finite element models to evaluate the likely residual and operating stress profiles remaining after FSWOL for typical dissimilar metal weld configurations, some of which are approved for leak-before-break (LBB) applications in pressurized water reactors. Circumferential cracks were modeled in the dissimilar metal weld area and forced to grow in order to evaluate their crack opening displacements and stress intensity factors vs. depth before and after weld overlay and before and after application of operating pressure and temperature.

An Analytical Evaluation of the Efficacy of the Mechanical Stress Improvement Process in Pressurized Water Reactor Primary Cooling Piping

2008 ◽  
Author(s):  
L. F. Fredette ◽  
Paul M. Scott ◽  
F. W. Brust
Keyword(s):  
Stress Corrosion ◽  
Mechanical Stress ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Pressurized Water Reactors ◽  
Pressurized Water ◽  
Water Reactor ◽  
Dissimilar Metal ◽  
Improvement Process ◽  
Water Reactors

The Mechanical Stress Improvement Process (MSIP) has been used successfully to mitigate intergranular stress corrosion cracking in boiling water reactor (BWR) welded stainless steel piping for many years. The MSIP technique creates compressive residual stresses at the inside surface of the welded joint while producing a slight permanent deformation of the pipe on one side of the weld. A prerequisite for use of MSIP on welded pipes susceptible to primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWR) is knowledge of the efficacy of the process when applied to dissimilar metal welds common to PWR primary cooling piping. This study uses two and three dimensional finite element models to evaluate the likely residual and operating stress profiles remaining after MSIP for typical dissimilar metal weld configurations, some of which are approved for leak-before-break (LBB) applications in pressurized water reactors.

Stress Corrosion Cracking (SCC) of Nickel-Base Weld Metals in PWR Primary Water

2013 ◽  
Vol 747-748 ◽  
pp. 723-732 ◽  
Author(s):  
Ru Xiong ◽  
Ying Jie Qiao ◽  
Gui Liang Liu
Keyword(s):  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Surface Condition ◽  
Cold Work ◽  
Corrosion Cracking ◽  
Pressurized Water ◽  
Weld Metals ◽  
Surface Residual Stresses ◽  
Primary Water

This discussion reviewed the occurrence of stress corrosion cracking (SCC) of alloys 182 and 82 weld metals in primary water (PWSCC) of pressurized water reactors (PWR) from both operating plants and laboratory experiments. Results from in-service experience showed that more than 340 Alloy 182/82 welds have sustained PWSCC. Most of these cases have been attributed to the presence of high residual stresses produced during the manufacture aside from the inherent tendency for Alloy 182/82 to sustain SCC. The affected welds were not subjected to a stress relief heat treatment with adjacent low alloy steel components. Results from laboratory studies indicated that time-to-cracking of Alloy 82 was a factor of 4 to 10 longer than that for Alloy 182. PWSCC depended strongly on the surface condition, surface residual stresses and surface cold work, which were consistent with the results of in-service failures. Improvements in the resistance of advanced weld metals, Alloys 152 and 52, to PWSCC were discussed.

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