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Design and Analysis

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

[+] Author and Article Information
Tao Zhang

e-mail: tzhang@emc-sq.com

Gery Wilkowski

3518 Riverside Drive, Suite 202,
Columbus, OH 43221

Ru-Feng Liu

Mechanical and System Engineering
Program (MSEP),
Institute of Nuclear Energy Research,
1000 Wenhua Road, Jiaan Village,
Longtan, Taoyuan 32546,
Taiwan (R.O.C)

Sam Ranganath

XGEN Engineering,
7173 Queensbridge Way,
San Jose, CA 95120-4081

Yao Long Tsai

Material and Chemical Research Laboratories,
Industrial Technology Research Institute,
Building 52, 195 Chung-Hsing Road, Section 4,
Chutung, Hsinchu 31040, Taiwan (R.O.C)

This series of analyses was conducted using ABAQUS 6.8. “(Avg. 75%)” in all contour plot legends is the threshold for averaging element output at nodes.

Axial stress in this paper defined in longitudinal direction while hoop stress is defined in circumferential direction, i.e., normal to finite element mesh. ID stands for inner diameter while OD where overlay was laid down stands for outer diameter of the pipe.

1Correspoding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNALOF PRESSURE VESSEL TECHNOLOGY. Manuscript received February 28, 2011; final manuscript received March 20, 2012; published online October 18, 2012. Assoc. Editor: Somnath Chattopdhyay.

J. Pressure Vessel Technol 134(6), 061205 (Oct 18, 2012) (14 pages) doi:10.1115/1.4006558 History: Received February 28, 2011; Revised March 20, 2012

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.

Copyright © 2012 by ASME
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References

Figures

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Fig. 1

Dimensional sketches and axisymmetric finite element model for surge nozzle

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Fig. 19

Dimensional sketches and axisymmetric finite element model for saftety/relief nozzle

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Fig. 18

Hoop plots of axial stresses in surge nozzle along i.d.

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Fig. 17

Line plots of hoop stresses in surge nozzle along thickness at weld center

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Fig. 16

Hoop stresses in surge nozzle at operating temperature 340 °C (644 °F) in MPa

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Fig. 15

Hoop stresses in surge nozzle after overlay in MPa

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Fig. 14

Hoop stresses in surge nozzle after stainless weld in MPa

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Fig. 13

Hoop stresses in surge nozzle after fill-in weld in MPa

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Fig. 12

Hoop stresses in surge nozzle after repair in MPa

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Fig. 11

Hoop stresses in surge nozzle after DMW in MPa

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Fig. 10

Line plots of axial stresses in surge nozzle along i.d.

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Fig. 9

Line plots of axial stresses in surge nozzle along thickness at weld center

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Fig. 8

Path definition of surge nozzle for line plots

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Fig. 7

Axial stresses in surge nozzle at operating temperature 340 °C (644 °F) in MPa

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Fig. 6

Axial stresses in surge nozzle after overlay in MPa

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Fig. 5

Axial stresses in surge nozzle after stainless weld in MPa

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Fig. 4

Axial stresses in surge nozzle after fill-in weld in MPa

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Fig. 3

Axial stresses in surge nozzle after repair in MPa

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Fig. 2

Axial stresses in surge nozzle after DMW in MPa

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Fig. 20

Axial stresses in safety/relief nozzle after DMW in MPa

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Fig. 21

Axial stresses in safety/relief nozzle after repair in MPa

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Fig. 22

Axial stresses in safety/relief nozzle after stainless weld in MPa

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Fig. 23

Axial stresses in safety/relief nozzle after overlay in MPa

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Fig. 24

Axial stresses in safety/relief nozzle at operating temperature 340 °C (644 °F) in MPa

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Fig. 25

Path definition of safety/relief nozzle for line plots

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Fig. 26

Line plots of axial stresses in safety/relief nozzle along thickness at weld center

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Fig. 27

Line plots of axial stresses in safety/relief nozzle along i.d.

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Fig. 28

Hoop stresses in safety/relief nozzle after repair in MPa

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Fig. 29

Hoop stresses in safety/relief nozzle after stainless weld in MPa

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Fig. 30

Hoop stresses in safety/relief nozzle after overlay in MPa

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Fig. 31

Hoop stresses in safety/relief nozzle at operating temperature 340 °C (644 °F) in MPa

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Fig. 32

Line plots of hoop stresses in safety/relief nozzle along thickness at weld center

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Fig. 33

Line plots of hoop stresses in safety/relief nozzle along i.d.

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Fig. 34

Geometric dimensions and axisymmetric finite element model for spray nozzle

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Fig. 36

Axial stresses in spray nozzle after stainless weld in MPa

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Fig. 37

Axial stresses in spray nozzle after overlay in MPa

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Fig. 38

Axial stresses in spray nozzle at operating temperature 340 °C (644 °F) in MPa

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Fig. 39

Path definition of spray nozzle for line plots

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Fig. 40

Line plots of axial stresses in spray nozzle along thickness at weld center

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Fig. 41

Line plots of axial stresses in spray nozzle along i.d.

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Fig. 42

Hoop stresses in spray nozzle after repair in MPa

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Fig. 43

Hoop stresses in spray nozzle after stainless weld in MPa

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Fig. 44

Hoop stresses in spray nozzle after overlay in MPa

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Fig. 45

Hoop stresses in spray nozzle at operating temperature 340 °C (644 °F) in MPa

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Fig. 46

Line plots of hoop stresses in spray nozzle along thickness at weld center

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Fig. 47

Line plots of hoop stresses in spray nozzle along i.d.

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Fig. 35

Axial stresses in spray nozzle after repair in MPa

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