Assessments of Residual Stress Due to Weld-Overlay Cladding and Structural Integrity of Reactor Pressure Vessel

2010 ◽  
Author(s):  
Jinya Katsuyama ◽  
Hiroyuki Nishikawa ◽  
Makoto Udagawa ◽  
Mitsuyuki Nakamura ◽  
Kunio Onizawa
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Stress Distribution ◽  
Structural Integrity ◽  
Base Material ◽  
Pressure Vessels ◽  
Residual Stress Distribution ◽  
Weld Overlay ◽  
Weld Residual Stress ◽  
Reactor Pressure

Austenitic stainless steel is cladded on the inner surface of ferritic low alloy steel of reactor pressure vessels (RPVs) for protecting the vessel walls against the corrosion. After the manufacturing process of the RPVs including weld-overlay cladding and post-weld heat treatments (PWHT), the residual stress still remain in such dissimilar welds. The residual stresses generated within the cladding and base material were measured as-welded and PWHT conditions using the sectioning and deep-hole-drilling (DHD) techniques. Thermal-elastic-plastic-creep analyses considering the phase transformation in heat affected zone using finite element method were also performed to evaluate the weld residual stress produced by weld overlay cladding and PWHT. By comparing analytical results with those measured ones, it was shown that there was a good agreement of residual stress distribution within the cladding and base material. Tensile residual stress in cladding is mostly due to the difference between the thermal expansions of cladding and base materials. It was also shown that taking the phase transformation during welding into account is important to improve the accuracy of weld residual stress analysis. Using the calculated residual stress distribution, fracture mechanics analysis for a postulated flaw during pressurized thermal shock (PTS) events have been performed. The effect of weld residual stress on the structural integrity of RPV was evaluated through some case studies. The result indicates that consideration of weld residual stress produced by weld-overlay cladding and PWHT is important for assessing the structural integrity of RPVs.

Assessment of Residual Stress Due to Overlay-Welded Cladding and Structural Integrity of a Reactor Pressure Vessel

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Jinya Katsuyama ◽  
Hiroyuki Nishikawa ◽  
Makoto Udagawa ◽  
Mitsuyuki Nakamura ◽  
Kunio Onizawa
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Stress Distribution ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Base Material ◽  
Residual Stress Distribution ◽  
Weld Residual Stress ◽  
Overlay Welding ◽  
Reactor Pressure

In this study, the residual stresses generated within the overlay-welded cladding and base material of reactor pressure vessel (RPV) steel were measured for as-welded and postwelded heat-treated conditions using the sectioning and deep-hole-drilling (DHD) techniques. In addition, thermo–elastic–plastic creep analyses considering the phase transformation in the heat-affected zone using the finite element method (FEM) were performed to evaluate the weld residual stress produced by overlay-welding and postweld heat treatment (PWHT). By comparing the analytical results with the experimentally determined values, we found a good agreement for the residual stress distribution within the cladding and the base material. The tensile residual stress in the cladding is largely due to the difference in the thermal expansion of the cladding and the base material. It was also shown that considering phase transformation during welding was important for improving the accuracy of the weld residual stress analysis. Using the calculated residual stress distribution, we performed fracture mechanics analyses for a vessel model with a postulated flaw during pressurized thermal shock (PTS) events. The effect of the weld residual stress on the structural integrity of RPVs was evaluated through some case studies. The results indicated that consideration of the weld residual stress produced by overlay-welding and PWHT is important for assessing the structural integrity of RPVs.

Investigation of Residual Stresses Caused by Welding, Cladding and Tempering of Reactor Pressure Vessels

2003 ◽  
Author(s):  
V. I. Kostylev ◽  
B. Z. Margolin ◽  
A. Y. Varovin ◽  
E. Keim
Keyword(s):  
Finite Element Method ◽  
Residual Stress ◽  
Finite Element ◽  
Stress Distribution ◽  
Weld Metal ◽  
Pressure Vessels ◽  
Residual Stress Distribution ◽  
Stress Fields ◽  
The Finite Element Method ◽  
Reactor Pressure

Calculations of residual stress fields, which arise after welding, cladding and tempering, were performed as applied to reactor pressure vessels (RPVs) of WWER types. These calculations are based on a procedure, which takes into account Feα↔Feγ transformation happening in base and weld metal under welding and cladding, and also creep during tempering. The procedure is based on solutions of the temperature and non-isothermal elasto-plastic problem with and without creep by the finite element method. On the basis of the performed investigation it is shown that Feα↔Feγ transformation may affect the residual stress distribution. An analysis of cases has been performed for which the above effect is strong and for which this effect may be ignored. On the basis of the calculation performed, an engineering procedure is proposed that allows to determine the residual stress fields in welds of the WWER-440 and WWER-1000 for various durations of post-weld tempering.

scholarly journals Residual Stress Distribution in Feal Weld Overlay on Steel

1994 ◽  
Vol 364 ◽  
Author(s):  
X.-L. Wang ◽  
S. Spooner ◽  
C. R. Hubbard ◽  
P. J. Maziasz ◽  
G. M. Goodwin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Residual Stress ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Post Weld Heat Treatment ◽  
Residual Stress Distribution ◽  
Element Analysis ◽  
Weld Overlay

AbstractNeutron diffraction was used to measure the residual stress distribution in an FeAl weld overlay on steel. It was found that the residual stresses accumulated during welding were essentially removed by the post-weld heat treatment that was applied to the specimen; most residual stresses in the specimen developed during cooling following the post-weld heat treatment. The experimental data were compared with a plasto-elastic finite element analysis. While some disagreement exists in absolute strain values, there is satisfactory agreement in strain spatial distribution between the experimental data and the finite element analysis.

Important Residual Stress Features in Reactor Nozzle Dissimilar Metal Welds

2011 ◽  
Author(s):  
Jinmiao Zhang ◽  
Shaopin Song ◽  
Pingsha Dong
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Nuclear Reactor ◽  
Residual Stress Distribution ◽  
Stress Distributions ◽  
Weld Overlay ◽  
Dissimilar Metal ◽  
Nozzle Length ◽  
Dissimilar Metal Weld ◽  
Metal Weld

This paper is focused on the study of residual stress distribution at a dissimilar metal weld (DMW) of nuclear reactor nozzle. The paper extends some of the recent research on this subject by investigating the effect of weld sequence and nozzle length design on the residual stress distributions. It also investigates the effect of a partial excavation repair and a weld overlay on the residual stress distribution. As a result, some of the important residual stress features at DMW are revealed and these features are discussed and summarized in the paper.

Residual Stress Assessment for Pressure Vessel Subject to Thermal Shock

2017 ◽  
Author(s):  
Jushin Hsiao ◽  
Haiyang Qian ◽  
Christopher Brunner ◽  
Thomas R. Bober ◽  
Lynn D’Amico ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Pressure Vessels ◽  
Residual Stress Distribution ◽  
Life Assessment ◽  
Systematic Analysis ◽  
Maximum Residual Stress ◽  
Film Coefficient ◽  
Assessment Procedures ◽  
Thermal Shocks

API 579-1/ASME FFS-1 Part 9 provides assessment procedures for evaluating crack-like flaws in components to determine if it is fit for continued service. Although residual stress distribution is required as an input to perform a fatigue life assessment, no procedure or guideline is available for evaluating this crack driving force resulting from thermal shocks. Through a systematic analysis, a conservative residual stress distribution can be obtained for pressure vessels subject to thermal shocks. For the two thick-walled vessels considered, the maximum residual stress occurs when the vessel is half filled with water. The conservative residual stress provides the needed input when using API 579-1/ASME FFS-1 for evaluating crack-like flaws in components. Dependence of the residual stress on film coefficient, temperature difference between water and metal surface, and water level inside the vessel is also presented so that refinement can be made on life assessment when additional field data becomes available.

scholarly journals Residual stress distribution in FeAl weld overlay on steel

10.2172/46697 ◽  
1994 ◽  
Author(s):  
X.L. Wang ◽  
S. Spooner ◽  
C.R. Hubbard ◽  
P.J. Maziasz ◽  
G.M. Goodwin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stress Distribution ◽  
Weld Overlay

Weld Residual Stress Analysis and the Effects of Structural Overlay on Various Nuclear Power Plant Nozzles

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Tao Zhang ◽  
Frederick W. Brust ◽  
Gery Wilkowski ◽  
Chin-Cheng Huang ◽  
Ru-Feng Liu ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Weld Overlay ◽  
Dissimilar Metal ◽  
Weld Residual Stress ◽  
Weld Material ◽  
Pipe Joints

Welding is a commonly used and one of the most important material-joining processes in industry. The incidences of defects had been located by ultrasonic testing in various pressurizer nozzle dissimilar metal welds (DMW) at nuclear power plants. In order to evaluate the crack propagation, it is required to calculate the stress distribution including weld residual stress and operational stress through the wall thickness in the weld region. The analysis procedure in this paper included not only the pass-by-pass welding steps but also other essential fabrication steps of surge, safety/relief, and spray nozzles. In this paper, detailed welding simulation analyses have been conducted to predict the magnitude of these stresses in the weld material. To prevent primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWR) on susceptible welded pipes with dissimilar metal welds, the weld overlay process has been applied to repair nuclear reactor pipe joints in plants. The objectives of such repairs are to induce compressive axial residual stresses on the pipe inside surface, as well as increase the pipe thickness with a weld material that is not susceptible to stress corrosion cracking. Hence, understanding the residual stress distribution is important to evaluate the reliability of pipe joints with weld overlay repairs. The finite element results in this paper showed that, after deposition of the DMW nozzle and stainless steel welds, tensile weld residual stresses still exist at regions of the DMW through the thickness. This tensile weld residual stress region was significantly reduced after welding the overlay. The overlay weld also provides a more uniform and large compressive region through the thickness, which has a beneficial effect on the structural integrity of the DMW in the plant.

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