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Research Papers: Fluid-Structure Interaction

Development of Boiling Water Reactor Steam Dryer Loading Evaluation Methods Through Scale Model Tests Under Actual Steam Conditions

[+] Author and Article Information
Shiro Takahashi

Hitachi Research Laboratory, Hitachi, Ltd.,
1-1 Omika, 7-chome,
Hitachi, Ibaraki 319-1292, Japan
e-mail: shiro.takahashi.fu@hitachi.com

Keita Okuyama

Hitachi Research Laboratory, Hitachi, Ltd.,
1-1 Omika, 7-chome,
Hitachi, Ibaraki 319-1292, Japan
e-mail: keita.okuyama.uu@hitachi.com

Akinori Tamura

Hitachi Research Laboratory, Hitachi, Ltd.,
1-1 Omika, 7-chome,
Hitachi, Ibaraki 319-1292, Japan
e-mail: akinori.tamura.mt@hitachi.com

Yasuhiro Mabuchi

Hitachi-GE Nuclear Energy, Ltd.,
1-1 Saiwai, 3-chome,
Hitachi, Ibaraki 317-8511, Japan
e-mail: yasuhiro.mabuchi.ep@hitachi.com

Teppei Kubota

Hitachi-GE Nuclear Energy, Ltd.,
1-1 Saiwai, 3-chome,
Hitachi, Ibaraki 317-8511, Japan
e-mail: teppei.kubota.cj@hitachi.com

Kazuhiro Yoshikawa

Hitachi-GE Nuclear Energy, Ltd.,
1-1 Saiwai, 3-chome,
Hitachi, Ibaraki 317-8511, Japan
e-mail: kazuhiro.yoshikawa.cv@hitachi.com

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received September 2, 2013; final manuscript received January 8, 2014; published online August 19, 2014. Assoc. Editor: Jong Chull Jo.

J. Pressure Vessel Technol 136(5), 051307 (Aug 19, 2014) (8 pages) Paper No: PVT-13-1151; doi: 10.1115/1.4026580 History: Received September 02, 2013; Revised January 08, 2014

Previous plant measurements and scale model tests have demonstrated that intense fluctuating pressure acted on the steam dryer in boiling water reactors (BWRs) at higher velocity flows than in normal operation. The cause of the dryer loading was considered as flow-induced acoustic resonance at the stub pipes of safety relief valves (SRVs) in the main steam lines (MSLs). Acoustic resonance was considered to be generated by the interaction between the sound field and the unstable shear layer across the opening of the side branches of the SRV stub pipes. Some air scale tests have been conducted and they are useful for evaluation of occurrence of acoustic resonance in SRV stub pipes and characteristics of fluctuating pressure in MSLs. However, it is possible that differences in pressure conditions and fluid properties may cause the dryer loading to be underestimated. In the present study, we conducted scale tests under actual steam conditions to evaluate the scale model test methods for BWR dryer loading estimation. The test apparatus consisted of a steam dryer, steam dome and 4 MSLs with 20 SRV stub pipes. We demonstrated that acoustic resonance occurred in the SRV stub pipes and the fluctuating pressure which propagated from the SRVs to the dryer caused fluctuating stress on the steam dryer at the SRV resonance frequency. Acoustic resonance started when Strouhal number decreased below 0.6 in both the scale model air and steam tests. The onset of resonance due to the single vortex mode was not influenced by pressure conditions and fluid properties. The increase of fluctuating pressure due to the double vortex mode which occurred at Strouhal number values from 0.8 to 0.9 could be clearly seen in the scale model steam tests unlike in the air tests. The results showed that the self-excited acoustic resonance was affected by the static pressure and fluid properties for the scale model air tests. However, no significant influence from steam pressure was seen at pressure higher than 3 MPa. Normalized fluctuating pressure was almost the same regardless of pressure. We verified that normalization by dynamic pressure in the main pipe was a reasonable approach for evaluation of fluctuating pressure in the SRV stub pipes. Increase of fluctuating pressure due to the double vortex mode was clearly distinguished in SRV stub pipes but not strong in the MSL pipes and had insignificant impact on the dryer loading.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

BWR steam dome, dryer, and MSLs. Dots in the upper view of the figure represent the locations of the SRVs.

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Fig. 2

Evaluation flow diagram

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Fig. 3

Flow-induced acoustic resonance at the SRV stub pipe

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Fig. 6

Schematic diagram of test loop

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Fig. 7

Schematic diagram of test apparatus

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Fig. 8

Evaluation locations

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Fig. 9

Influence of Re on fluctuating pressure for a single SRV stub pipe (CFD results)

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Fig. 10

Frequency spectra of fluctuating pressure and strain (St = 0.55, P = 7 MPa)

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Fig. 11

Influence of Strouhal number (P = 7 MPa)

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Fig. 12

Results of air tests [2] (P = 0.1 MPa)

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Fig. 13

Vortex modes in SRV stub pipes

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Fig. 14

Influence of pressure on fluctuating pressure in SRV stub pipes

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Fig. 15

Variation of frequency of fluctuating pressure (P = 7 MPa)

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