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Research Papers: Fluid-Structure Interaction

Numerical Calculation of Shear Stress Distribution on the Inner Wall Surface of CANDU Reactor Feeder Pipe Conveying Two-Phase Coolant

[+] Author and Article Information
Jong Chull Jo1

 Korea Institute of Nuclear Safety, 19 Kusung-dong, Yusung-gu, Taejon 305-338, Koreajcjo@kins.re.kr

Dong Gu Kang, Kyung Wan Roh

 Korea Institute of Nuclear Safety, 19 Kusung-dong, Yusung-gu, Taejon 305-338, Korea

1

Corresponding author.

J. Pressure Vessel Technol 131(2), 021301 (Dec 10, 2008) (13 pages) doi:10.1115/1.3008038 History: Received August 14, 2007; Revised May 07, 2008; Published December 10, 2008

Two-phase flow fields inside feeder pipes of a CANada Deuterium Uranium (CANDU) reactor have been simulated numerically using a computational fluid dynamics (CFD) code to calculate the shear stress distribution, which is the most important factor to be considered in predicting the local areas of feeder pipes highly susceptible to flow-accelerated corrosion (FAC)-induced wall thinning. The CFD approach with schemes used in this study to simulate the turbulent flow situations inside the CANDU feeder pipes has been verified by showing a good agreement between the investigation results for the failed feedwater pipe at Surry Unit 2 plant in the U.S. and the CFD calculation. Sensitivity studies of the three geometrical parameters such as angle of the first and second bends, length of the first span between the grayloc hub and the first bend, and length of the second span between the first and second bends had already been performed. In this study, the effects of void fraction of the primary coolant coming out from the exit of pressure tubes containing nuclear fuel on the fluid shear stress distribution at the inner surface of the feeder pipe wall have been investigated to find out the local areas of feeder pipes conveying a two-phase coolant, which are highly susceptible to FAC-induced wall thinning. From the results of the CFD analysis, it is seen that the local regions of feeder pipes of the operating CANDU reactors in Korea, on which the wall thickness measurements have been performed so far, do not coincide with the worst regions predicted by the present CFD analysis, which is the connection region of straight and bend pipes near the inlet part of the bend intrados. Finally, based on the results of the present CFD analysis, a guide to the selection of the weakest local positions where the measurement of wall thickness should be performed with higher priority has been provided.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 5

(a) Comparison of wall shear distribution between a real feeder pipe model and its simplified model for type 4B feeder pipe (b) Comparison of wall shear distribution between a real feeder pipe model and its simplified model for type 5A feeder pipe (c) Comparison of wall shear distribution between a real feeder pipe model and its simplified model for type 10A feeder pipe (d) Comparison of wall shear distribution between a real feeder pipe model and its simplified model for type 11B feeder pipe

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Figure 6

Effects of the bend angle of type A feeder pipe on the pressure drop and maximum wall shear

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Figure 7

Effects of the bend angle of type A feeder pipe on the location subjected to the maximum wall shear

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Figure 8

Effects of the first straight span length of type A feeder pipe on the pressure drop and maximum wall shear

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Figure 9

Effects of the first straight span length of type A feeder pipe on the location subjected to the maximum wall shear

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Figure 10

Effects of the second straight span length of type A feeder pipe on the pressure drop and maximum wall shear

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Figure 11

Effects of the second straight span length of type A feeder pipe on the location subjected to the maximum wall shear

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Figure 12

Void fraction distributions on the symmetry plane Z=0 of the feeder pipe type A

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Figure 13

Void fraction distributions at the wall cross sections of the feeder pipe type A (α=0.1)

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Figure 14

Fluid shear stress distributions on the inner wall surface of the feeder pipe type A

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Figure 15

Effects of the void fraction on the local positions of the feeder pipe A inner wall surface subjected to the maximum fluid shear stress

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Figure 16

Effect of the void fraction of type A feeder pipe on the maximum wall shear

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Figure 17

Effects of the first straight span length of type B feeder pipe on the pressure drop and maximum wall shear

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Figure 18

Effects of the bend angle of type B feeder pipe on the location subjected to the maximum wall shear

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Figure 19

Effects of the first straight span length of type B feeder pipe on the pressure drop and maximum wall shear

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Figure 20

Effects of the first straight span length of type B feeder pipe on the location subjected to the maximum wall shear

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Figure 21

Void fraction distributions on the symmetry plane Z=0 of the feeder pipe type B

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Figure 22

Void fraction distributions at the wall cross sections of the feeder pipe type B (α=0.1)

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Figure 23

Fluid shear stress distributions on the inner wall surface of the feeder pipe type B

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Figure 24

Effects of the void fraction on the local positions of the feeder pipe B inner wall surface subjected to the maximum fluid shear stress

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Figure 25

Effect of the void fraction of type B feeder pipe on the maximum wall shear

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Figure 1

Schematic geometry and data of pressure tube and feeder pipe of type 1

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Figure 2

Present monitoring points of feeder pipes

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Figure 3

Two categories by the direction of the first bend outlet: (a) first bend winds in the upstream direction of the pressure tube, (b) first bend winds in the downstream direction of the pressure tube

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Figure 4

System models for selected feeder pipes: (a) type 4B, (b) type 5A, (c) type 10A, and (d) type 11B

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