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Research Papers: Design and Analysis

Welding Residual Stress Solutions for Dissimilar Metal Surge Line Nozzle Welds

[+] Author and Article Information
D. Rudland2

Office of Nuclear Regulatory Research, US Nuclear Regulatory Commission, Mail Stop: C-05C07M, Washington, DC 20555-0001david.rudland@nrc.gov

A. Csontos

Office of Nuclear Regulatory Research, US Nuclear Regulatory Commission, Mail Stop: C-05C07M, Washington, DC 20555-0001

T. Zhang, G. Wilkowski

 Engineering Mechanics Corporation of Columbus, 3518 Riverside Drive, Suite 202, Columbus, OH 43221

A step change annealing model was assumed.

The thermal sleeve was not included in the analyses.

The fill-in weld is used to seat the thermal sleeve in some surge nozzles.

The stress path used in Ref. 2 is a radial cut that runs through the butter 6.35 mm from the DM weld.

The yield strength of the weld was increased to match that which was used in Ref. 2.

2

Corresponding author.

J. Pressure Vessel Technol 132(2), 021208 (Mar 31, 2010) (7 pages) doi:10.1115/1.4000701 History: Received November 20, 2008; Revised November 16, 2009; Published March 31, 2010; Online March 31, 2010

At the end of 2006, defects were identified using ultrasonic testing in three of the pressurizer nozzle dissimilar metal (DM) welds at the Wolf Creek nuclear power plant. Understanding welding residual stress is important in the evaluation of why and how these defects occur, which in turn helps to determine the reliability of nuclear power plants. This paper presents analytical predictions of welding residual stress in the surge nozzle geometry identified at Wolf Creek. The analysis procedure in this paper includes not only the pass-by-pass welding steps, but also other essential fabrication steps of pressurizer surge nozzles. Detailed welding simulation analyses have been conducted to predict the magnitude of these stresses in the weld material. Case studies were carried out to investigate the change in the DM main weld stress fields resulting from different boundary conditions, material strength, weld sequencing, as well as simulation of the remaining piping system stiffness. A direct comparison of these analysis methodologies and results has been made in this paper. Weld residual stress results are compared directly to those calculated by the nuclear industry.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

True stress-strain curves for Alloy 182 weld metal

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Figure 2

Surge nozzle finite element model

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Figure 3

Surge nozzle weld details: (a) main dissimilar metal weld and (b) stainless steel safe-end weld

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Figure 4

Axial stress for the surge nozzle case without a stainless steel weld at 340°C(644°F) with left-to-right weld sequence and no repair. (Arrow indicates the straight-line path of maximum stress in the weld material.)

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Figure 5

Axial stress for the surge nozzle case without a stainless steel weld at 340°C(644°F) with right-to-left weld sequence and no repair. (Arrow indicates the straight-line path of maximum stress in the weld material.)

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Figure 6

Axial stress for the surge nozzle case with weld repair but without a stainless steel weld at 340°C(644°F). (Arrow indicates the straight-line path of maximum stress in the weld material.)

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Figure 7

Comparison of surge nozzle WRS (left-to-right weld sequence) with no repairs, and with and without a stainless steel safe-end weld at operating temperature (open symbols from Ref. 2)

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Figure 8

Comparison of surge nozzle WRS (left-to-right weld sequence) with repair, and with and without the stainless steel safe-end weld at operating temperature

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Figure 9

Effect of the fill-in weld sequence for surge nozzle WRS at operating temperature (square symbols from Ref. 2)

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Figure 10

Location of section for direct comparison of surge nozzle results

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Figure 11

Comparison of surge nozzle axial residual stresses before the fill-in weld

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Figure 12

Comparison of surge nozzle axial residual stress with no safe-end weld and no repair along the path described in Fig. 1 at operating temperature

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Figure 13

Change in axial stress as a stainless steel weld is added

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Figure 14

Axial stress in the DM weld with and without spring to model system compliance

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Figure 15

The stainless steel weld with (a) original and (b) lumped passes

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Figure 16

Axial stress (at 340°C(644°F)) in the center of the DM weld due to weld sequence of the SS weld. The DM weld not simulated in this case.

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Figure 17

Contours of axial stress (in MPa) in the DM weld from the welding of the stainless steel safe-end. The DM weld not simulated in this case.

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