Analysis of Residual Stresses in a Pressurizer Surge–Nozzle Weldment

2011 ◽  
Author(s):  
Florian Obermeier ◽  
Tomas Nicak ◽  
Gottfried Meier ◽  
Elisabeth Keim
Keyword(s):  
Residual Stresses ◽  
Material Model ◽  
Round Robin ◽  
Pressurized Water Reactor ◽  
Element Analysis ◽  
Pressurized Water ◽  
Piping Systems ◽  
Primary Water ◽  
Abaqus Code ◽  
Transient Thermal

Residual stresses and distortion of welded structures have a significant influence on their functionality and their lifetime. In Pressurized Water Reactor (PWR) piping systems, residual stresses in dissimilar metal welds extensively increase their susceptibility to primary water stress corrosion cracking (PWSCC). An accurate crack initiation and growth assessment is essential to assure that no severe component failure will occur due to SCC or any other stress induced mechanism. Therefore it is necessary to develop methods for a proper residual stress and distortion prediction. Numerical welding simulations have developed fast during the recent years but no universally accepted guidelines for a reliable prediction of residual stresses have been established so far. In order to support further validation of developed methods the U.S. NRC launched an international round robin program. Its main intention is to benchmark different numerical approaches by direct comparison with experimental data obtained from a provided mock-up. This paper shows the contribution of AREVA NP Germany to this round robin. A two dimensional axis-symmetric analysis of a pressurizer surge nozzle – safe end – pipe weldment will be presented. The residual stresses are calculated by means of an uncoupled transient thermal and mechanical finite element analysis using the ABAQUS Code. In addition some comments on the selection of the material model and its effect on the resulting residual stresses will be given.

3D Residual Stress Simulation of an Excavate and Weld Repair Mockup

2016 ◽  
Author(s):  
Francis H. Ku ◽  
Pete C. Riccardella ◽  
Steven L. McCracken
Keyword(s):  
Residual Stresses ◽  
Weld Metal ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Weld Repair ◽  
Element Analysis ◽  
Pressurized Water ◽  
Piping Systems ◽  
Asme Code ◽  
Original Construction

This paper presents predictions of weld residual stresses in a mockup with a partial arc excavate and weld repair (EWR) utilizing finite element analysis (FEA). The partial arc EWR is a mitigation option to address stress corrosion cracking (SCC) in nuclear power plant piping systems. The mockup is a dissimilar metal weld (DMW) consisting of an SA-508 Class 3 low alloy steel forging buttered with Alloy 182 welded to a Type 316L stainless steel plate with Alloy 82/182 weld metal. This material configuration represents a typical DMW of original construction in a pressurized water reactor (PWR). After simulating the original construction piping joint, the outer half of the DMW is excavated and repaired with Alloy 52M weld metal to simulate a partial arc EWR. The FEA performed simulates the EWR weld bead sequence and applies three-dimensional (3D) modeling to evaluate the weld residual stresses. Bi-directional weld residual stresses are also assessed for impacts on the original construction DMW. The FEA predicted residual stresses follow expected trends and compare favorably to the results of experimental measurements performed on the mockup. The 3D FEA process presented herein represents a validated method to evaluate weld residual stresses as required by ASME Code Case N-847 for implementing a partial arc EWR, which is currently being considered via letter ballot at ASME BPV Standards Committee XI.

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.

Numerical Modeling and Analytical Investigation of Autofrettage Process on the Fluid End Module of Fracture Pumps

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Mahdi Kiani ◽  
Roger Walker ◽  
Saman Babaeidarabad
Keyword(s):  
Residual Stresses ◽  
Kinematic Hardening ◽  
Analytical Formula ◽  
Strain Analysis ◽  
Material Model ◽  
Analytical Investigation ◽  
Stress Strain ◽  
Element Analysis ◽  
Hardening Material ◽  
Strain Evolution

One of the most important components in the hydraulic fracturing is a type of positive-displacement-reciprocating-pumps known as a fracture pump. The fluid end module of the pump is prone to failure due to unconventional drilling impacts of the fracking. The basis of the fluid end module can be attributed to cross bores. Stress concentration locations appear at the bores intersections and as a result of cyclic pressures failures occur. Autofrettage is one of the common technologies to enhance the fatigue resistance of the fluid end module through imposing the compressive residual stresses. However, evaluating the stress–strain evolution during the autofrettage and approximating the residual stresses are vital factors. Fluid end module geometry is complex and there is no straightforward analytical solution for prediction of the residual stresses induced by autofrettage. Finite element analysis (FEA) can be applied to simulate the autofrettage and investigate the stress–strain evolution and residual stress fields. Therefore, a nonlinear kinematic hardening material model was developed and calibrated to simulate the autofrettage process on a typical commercial triplex fluid end module. Moreover, the results were compared to a linear kinematic hardening model and a 6–12% difference between two models was observed for compressive residual hoop stress at different cross bore corners. However, implementing nonlinear FEA for solving the complicated problems is computationally expensive and time-consuming. Thus, the comparison between nonlinear FEA and a proposed analytical formula based on the notch strain analysis for a cross bore was performed and the accuracy of the analytical model was evaluated.

Prediction of Weld Residual Stress in a Pressurized Water Reactor Pressurizer Surge Nozzle

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Akira Maekawa ◽  
Atsushi Kawahara ◽  
Hisashi Serizawa ◽  
Hidekazu Murakawa
Keyword(s):  
Residual Stress ◽  
Heat Source ◽  
High Speed ◽  
Nuclear Regulatory Commission ◽  
Round Robin ◽  
Welding Residual Stress ◽  
3D Analysis ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor

Primary water stress corrosion cracking (PWSCC) phenomenon in dissimilar metal welds is one of the safety issues in ageing pressurized water reactor (PWR) piping systems. It is well known that analysis accuracy of cracking propagation due to PWSCC depends on welding residual stress conditions. The U.S. Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) carried out an international round robin validation program to evaluate and quantify welding residual stress analysis accuracy and uncertainty. In this paper, participation results of the authors in the round robin program were reported. The three-dimensional (3D) analysis based on a fast weld simulation using an iterative substructure method (ISM), was shown to provide accurate results in a high-speed computation. Furthermore, the influence of different heat source models on analysis results was investigated. It was demonstrated that the residual stress and distortion calculated using the moving heat source model were more accurate.

Cyclic Ramberg-Osgood Parameters of 316SS Weld Metal Under In-Air and PWR-Water Environments

2021 ◽  
Author(s):  
Jae Phil Park ◽  
Subhasish Mohanty ◽  
Chi Bum Bahn
Keyword(s):  
Room Temperature ◽  
Cyclic Plasticity ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Shakedown Analysis ◽  
Life Estimation ◽  
Fatigue Life Estimation ◽  
Tensile Curve ◽  
Asme Code ◽  
Primary Water

Abstract At present the available Ramberg-Osgood (R-O) parameters for different metals (e.g. in ASME code and other literature) are static (generally based on a tensile curve). These static R-O parameters cannot accurately model the cyclic plasticity behavior. This work presents the cyclic R-O material hardening parameters for 316 stainless steel similar metal welds. The parameters were estimated under various conditions (in-air at room temperature, 300°C in-air, and in-air at primary water conditions for a pressurized water reactor (PWR)). It is anticipated that the reported results would be useful for computational mechanics based shakedown analysis and fatigue life estimation of PWR components.

Examinations of Oxidation and Sulfidation of Grain Boundaries in Alloy 600 Exposed to Simulated Pressurized Water Reactor Primary Water

2013 ◽  
Vol 19 (3) ◽  
pp. 676-687 ◽  
Author(s):  
D.K. Schreiber ◽  
M.J. Olszta ◽  
D.W. Saxey ◽  
K. Kruska ◽  
K.L. Moore ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Atom Probe Tomography ◽  
Atom Probe ◽  
Alloy 600 ◽  
Pressurized Water Reactor ◽  
Intergranular Attack ◽  
Pressurized Water ◽  
Primary Water

AbstractHigh-resolution characterizations of intergranular attack in alloy 600 (Ni-17Cr-9Fe) exposed to 325°C simulated pressurized water reactor primary water have been conducted using a combination of scanning electron microscopy, NanoSIMS, analytical transmission electron microscopy, and atom probe tomography. The intergranular attack exhibited a two-stage microstructure that consisted of continuous corrosion/oxidation to a depth of ~200 nm from the surface followed by discrete Cr-rich sulfides to a further depth of ~500 nm. The continuous oxidation region contained primarily nanocrystalline MO-structure oxide particles and ended at Ni-rich, Cr-depleted grain boundaries with spaced CrS precipitates. Three-dimensional characterization of the sulfidized region using site-specific atom probe tomography revealed extraordinary grain boundary composition changes, including total depletion of Cr across a several nm wide dealloyed zone as a result of grain boundary migration.

Advanced Inlay System for Inlet/Outlet Nozzles of RV for Preventive Maintenance Against Alloy 600 PWSCC in Japanese PWR Plants

2013 ◽  
Author(s):  
Kazuhide Yamamoto ◽  
Masahiko Kizawa ◽  
Hiroki Kawazoe ◽  
Yuki Kobayashi ◽  
Ken Onishi ◽  
...  
Keyword(s):  
Preventive Maintenance ◽  
Heat Treatments ◽  
Residual Tensile Stress ◽  
Alloy 600 ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Loss Of Coolant Accident ◽  
Nuclear Plants ◽  
Alloy 690 ◽  
Primary Water

Because many nuclear plants have been in operation for ages, the importance of preventive maintenance technologies is getting higher. One conspicuous problem found in pressurized water reactor (PWR) plants is the primary water stress corrosion cracking (PWSCC) observed in Alloy 600 (a kind of high nickel based alloy) parts. Alloy 600 was used for butt welds between low alloy steel and stainless steel of nozzles of Reactor Vessel (RV), Steam Generator (SG), and Pressurizer (Pz). As PWSCC occurred at these parts may cause Loss of Coolant Accident (LOCA), preventive maintenance is necessary. PWSCC is considered to be caused by a mixture of three elements: high residual tensile stress on surface, material (Alloy 600) and environment. PWSCC can be prevented by improving one of the elements. MHI has been developing stress improvement methods, for example, Water Jet Peening (WJP), Shot Peening by Ultrasonic vibration (USP), and Laser Stress Improvement Process (L-SIP). According to the situation, appropriate method is applied for each part. WJP has been applied for RV nozzles of a lot of plants in Japan. However PWSCC was observed in RV nozzles during the inspection before WJP in recent years, MHI developed the Advanced INLAY system to improve the material from Alloy 600 to Alloy 690. Alloy 600 on the inner surface of the nozzles is removed and welding with Alloy 690 is performed. In addition, heat treatments for the nozzles are difficult for its structural situation, so ambient temperature temper bead welding technique for RV nozzles was developed to make the heat treatments unnecessary. This paper describes the specifications of the advanced INLAY system and introduces the maintenance activities which MHI has applied for three plants in Japan by March 2012.

SCC Propagation Analyses in a Welded Joint Under Various Assumed Residual Stresses and Anisotropic SCC Propagation Law

2018 ◽  
Author(s):  
Hiroshi Okada ◽  
Manabu Kikuchi ◽  
Masahiro Ono ◽  
Yasunori Yusa ◽  
Masayuki Kamaya
Keyword(s):  
Residual Stresses ◽  
Weld Metal ◽  
Welded Joint ◽  
Stress Distributions ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Young’S Moduli ◽  
Propagation Law ◽  
Cracked Structures ◽  
Automatic Mesh

In this paper, the results of evaluations of the stress intensity factor and of natural SCC (stress corrosion cracking) growth simulations under weld residual stresses are presented. The results reveal some characteristic SCC propagation behaviors. A surface crack is assumed at the welded joint of a mock-up of a pressurized water reactor (PWR) pressurizer nozzle. SCC propagation law for the weld metal is assumed to be anisotropic. SCC propagation in the surface direction is assumed to be 10 times slower than that in the thickness direction of the welded joint. The anisotropy is caused by different solidification rates of the weld metal in these directions. The material in terms of mechanical properties is set to be homogeneous as differences in the Young’s moduli and the Poisson’s ratios are not large between the weld and the mother metal. The analytical procedures based on the finite element method with an automatic mesh generation scheme for cracked structures, the results of analyses under a various residual stress distributions and some discussions are presented in this paper.

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