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Research Papers: Design and Analysis

Investigation on Constraint Effect of a Reactor Pressure Vessel Subjected to Pressurized Thermal Shocks

[+] Author and Article Information
Guian Qian

Laboratory for Nuclear Materials,
Nuclear Energy and Safety Department,
Paul Scherrer Institute,
Villigen 5232, Switzerland
e-mail: guian.qian@psi.ch

Markus Niffenegger

Laboratory for Nuclear Materials,
Nuclear Energy and Safety Department,
Paul Scherrer Institute,
Villigen 5232, Switzerland

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received September 21, 2013; final manuscript received July 10, 2014; published online September 15, 2014. Assoc. Editor: Albert E. Segall.

J. Pressure Vessel Technol 137(1), 011204 (Sep 15, 2014) (7 pages) Paper No: PVT-13-1168; doi: 10.1115/1.4028017 History: Received September 21, 2013; Revised July 10, 2014

The integrity of a reactor pressure vessel (RPV) related to pressurized thermal shocks (PTSs) has been extensively studied. This paper introduces the method of using fracture mechanics for the integrity analysis of a RPV subjected to PTS transients. A 3-D finite element (FE) model is used to perform thermal and fracture mechanics analyses by considering both elastic and elastic–plastic material models. The results show that the linear elastic analysis leads to a more conservative result than the elastic–plastic analysis. The variation of the T-stress and Q-stress (crack tip constraint loss) of a surface crack in a RPV subjected to PTSs is studied. A shallow crack is assumed in the RPV and the corresponding constraint effect on fracture toughness of the material is quantified by the K–T method. The safety margin of the RPV is larger based on the K–T approach than based only on the K approach. The J–Q method with the modified boundary layer formulation (MBL) is used for the crack tip constraint analysis by considering elastic–plastic material properties. For all transient times, the real stress is lower than that calculated from small scale yielding (SSY) due to the loss of crack tip constraint.

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Figures

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Fig. 1

Physical model of a RPV with an axial crack

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Fig. 2

3-D model of the beltline region of the RPV for thermal analysis. Due to the symmetry conditions, only one quarter of the circumference is modeled.

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Fig. 3

MLOCA and SLOCA transients (a) water temperature history and (b) pressure and water heat transfer coefficient histories

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Fig. 4

Temperature distributions through the vessel wall (a) during the MLOCA transient and (b) during the SLOCA transient

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Fig. 5

(a) The relationship between the Q-stress and normalized T-stress (b) the normalized opening-mode stress versus Q-stress for different radial distances

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Fig. 6

Temperature distributions through the vessel wall (a) during the MLOCA transient and (b) during the SLOCA transient

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Fig. 7

SIF and T-stress distributions (a) during the MLOCA transient and (b) during the SLOCA transient

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Fig. 8

Comparison of KI and KIC during the MLOCA transient with and without considering the constraint effect, KIC is modeled by the Master curve method

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Fig. 9

Comparison of SIF during the MLOCA and SLOCA transients by considering elastic and elastic–plastic material properties

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Fig. 10

Opening-mode stress distribution near the crack tip at different transient times (a) during the MLOCA and (b) during the SLOCA

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