Effect of Irradiation on Stress-Corrosion Cracking and Corrosion in Light Water Reactors

2006 ◽  
pp. 386-414 ◽  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Light Water Reactors ◽  
Light Water ◽  
Water Reactors

Understanding the Threshold Conditions for Stress Corrosion Cracking in Light Water Reactor Environments Based on the Deformation/Oxidation Mechanism

2007 ◽  
Author(s):  
Tetsuo Shoji ◽  
Zhanpeng Lu ◽  
Yoichi Takeda
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Oxidation Mechanism ◽  
Corrosion Cracking ◽  
Light Water ◽  
Threshold Conditions ◽  
Water Reactors

Stress corrosion cracking of structural materials is an important issue in light water reactors such as pressurized water reactors (PWR) and boiling water reactors (BWR). Proper disposition of the crack growth rate in terms of the engineering parameters is crucial for safe and economic long term operation. Threshold values of the stress intensity factor (K) have been used in some crack growth rate disposition guidelines such as JSME S NA1-2004 for austenitic stainless steels in BWR environments and flaw evaluation methodologies such as ASME XI Nonmandatory Appendix O-3230 for nickel-based Alloy 600 in PWR primary water environments. These threshold K values are based on the presently available experimental data that have been obtained mostly at relatively high K values. The threshold conditions for stress corrosion cracking in high temperature water are discussed more broadly for different cracking systems with various key-controlling parameters. The deformation/oxidation mechanism, which has been applied to quantification of the crack growth rate, is used here for analyzing the threshold conditions for stress corrosion cracking resulting from the interaction between the material and the environment under loading conditions.

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.

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