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Research Papers: Materials and Fabrication

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

[+] Author and Article Information
Akira Maekawa

Institute of Nuclear Safety System, Inc.,
64 Sata, Mihama-cho,
Mikata-gun, Fukui 919-1205, Japan
e-mail: maekawa@inss.co.jp

Atsushi Kawahara

Joining and Welding Research Institute,
Osaka University,
11-1 Mihogaoka,
Ibaraki, Osaka 567-0047, Japan
e-mail: Kawahara@jwri.osaka-u.ac.jp

Hisashi Serizawa

Joining and Welding Research Institute,
Osaka University,
11-1 Mihogaoka,
Ibaraki, Osaka 567-0047, Japan
e-mail: serizawa@jwri.osaka-u.ac.jp

Hidekazu Murakawa

Joining and Welding Research Institute,
Osaka University,
11-1 Mihogaoka,
Ibaraki, Osaka 567-0047, Japan
e-mail: murakawa@jwri.osaka-u.ac.jp

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received December 1, 2014; final manuscript received August 11, 2015; published online October 6, 2015. Assoc. Editor: Xian-Kui Zhu.

J. Pressure Vessel Technol 138(2), 021401 (Oct 06, 2015) (11 pages) Paper No: PVT-14-1196; doi: 10.1115/1.4031376 History: Received December 01, 2014; Revised August 11, 2015

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.

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References

Figures

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Fig. 3

Flow chart of iteration

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Fig. 2

Region division defined in the ISM for (a) estimating the stiffness and (b) calculating the stress: A, whole region and quasilinear property region; A-B, whole region and linear property region; B, local region and nonlinear property region; and Γ, boundary between A-B and B

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Fig. 1

Pressurizer and its surge nozzle

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Fig. 4

Sketch of pressurizer surge nozzle

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Fig. 6

Cross-sectional view of the model and materials used

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Fig. 7

Material constants: (a) thermal conductivity, (b) specific heat, (c) density, (d) thermal expansion coefficient, (e) Young's modulus, (f) Poisson's ratio, (g) initial yield stress, and (h) strain hardening modulus

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Fig. 8

Locations of thermocouples (TC1–TC6)

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Fig. 10

Time history of temperature calculated using fixed heat source model in the welding for SAFE END WELD and BACK WELD: (a) temperature on the outer surface and (b) temperature on the inner surface

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Fig. 9

Time history of temperature calculated using moving heat source model in the welding for SAFE END WELD and BACK WELD, (a) temperature on the outer surface and (b) temperature on the inner surface

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Fig. 11

Residual stress calculated using the moving heat source model (0 deg and 180 deg cross section): (a) hoop stress, (b) axial stress, and (c) radial stress

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Fig. 12

Residual stress calculated using the fixed heat source model (0 deg and 180 deg cross section): (a) hoop stress, (b)axial stress, and (c) radial stress

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Fig. 13

Residual stress in a circumferential cross section in the center of the weld part obtained using the moving heat source model: (a) hoop stress, (b) axial stress, and (c) radial stress

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Fig. 14

Residual stress in a circumferential cross section in the center of the weld part obtained using the fixed heat source model (0 deg and 180 deg cross section): (a) hoop stress, (b) axial stress, and (c) radial stress

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Fig. 15

Comparison between analysis and measurement for residual stress distribution in the through-thickness direction in the center of a dissimilar weld: (a) hoop stress and (b) axial stress

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Fig. 16

Comparison between heat source models for residual stress distribution in the through-thickness direction in the center of a dissimilar weld: (a) hoop stress, (b) axial stress, and (c) radial stress

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Fig. 17

Locations of weld distortion measurement

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Fig. 18

Comparison of weld distortion in point-to-point

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