Research Papers

Experimental Study on Cavitation of a Liquid Lithium Jet for International Fusion Materials Irradiation Facility

[+] Author and Article Information
Hiroo Kondo

National Institutes for Quantum and
Radiological Science and Technology,
801-1 Mukoyama,
Naka, Ibaraki 311-0193, Japan
e-mail: kondo.hiroo@qst.go.jp

Takuji Kanemura

National Institutes for Quantum and Radiological
Science and Technology,
801-1 Mukoyama,
Naka, Ibaraki 311-0193, Japan
e-mail: kanemura.takuji@qst.go.jp

Tomohiro Furukawa

Japan Atomic Energy Agency,
4002 Narita,
Oarai, Ibaraki 311-1393, Japan
e-mail: furukawa.tomohiro@jaea.go.jp

Yasushi Hirakawa

Japan Atomic Energy Agency,
4002 Narita,
Oarai, Ibaraki 311-1393, Japan
e-mail: hirakawa.yasushi@jaea.go.jp

Eiichi Wakai

Japan Atomic Energy Agency,
765-1 Funaishikawa,
Tokai, Ibaraki 319-1184, Japan
e-mail: wakai.eiichi@jaea.go.jp

Juan Knaster

Project Team,
2-166 Omotedate, Obuchi, Rokkasho-mura,
Kamikita-gun, Aomori 039-3212, Japan
e-mail: Juan.Knaster@ifmif.org

1Corresponding author.

2Present address: Michigan State University, East Lansing, Michigan.

Manuscript received April 26, 2016; final manuscript received April 4, 2017; published online July 31, 2017. Assoc. Editor: Lin-wen Hu.

ASME J of Nuclear Rad Sci 3(4), 041005 (Jul 31, 2017) (11 pages) Paper No: NERS-16-1045; doi: 10.1115/1.4036513 History: Received April 26, 2016; Revised April 04, 2017

A liquid Li jet flowing at 15 m/s under a high vacuum of 10−3 Pa is intended to serve as a beam target (Li target) in the planned International Fusion Materials Irradiation Facility (IFMIF). The engineering validation and engineering design activities (EVEDA) for the IFMIF are being implemented under the broader approach (BA) agreement. As a major activity of the Li target facility, the EVEDA Li test loop (ELTL) was constructed by the Japan Atomic Energy Agency. A stable Li target under the IFMIF conditions (Li temperature: 523.15 K, velocity: 15 m/s, and vacuum pressure: 10−3 Pa) was demonstrated using ELTL. This study focuses on a cavitationlike acoustic noise detected in a downstream conduit where the Li target flowed under vacuum conditions. This noise was investigated using acoustic-emission (AE) sensors installed at eight locations via acoustic wave guides. The sound intensity of the acoustic noise was examined against the cavitation number of the Li target. In addition, two types of frequency analysis, namely, fast Fourier transform (FFT) and continuous wavelet transform (CWT), were performed to characterize the acoustic noise. Owing to the acoustic noise's intermittency, high frequency, and the dependence on cavitation number, we conclude that this acoustic noise is generated when cavitation bubbles collapse and/or the structural material of the pipe is cracked because of the collapse of cavitation bubbles (cavitation pitting). The location of the cavitation was fundamental for presuming the mechanism. In this study, the propagation of acoustic waves among AE sensors placed at three locations was used to localize the cavitation and a method to determine the location of cavitation was formulated. As a result, we found that cavitation occurred only in a narrow area where the Li target impinged on the downstream conduit; therefore, we concluded that this cavitation was induced by the impingement. The design of the downstream conduit of the IFMIF Li target facility should be tackled in future based on information obtained in this study.

Copyright © 2017 by ASME
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Fig. 1

EVEDA Li test loop: (a) overall picture and (b) outlined P&ID of main Li loop

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Fig. 2

Configuration of target assembly (right) and picture of Li target (left)

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Fig. 3

Frequency sensitivity of an AE sensor

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Fig. 4

Configuration of downstream pipe, and location and configuration of transmission bars

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Fig. 5

Voltage signal of AE sensors at 15 m/s: (a) V = 15 m/s, P = 83 kPa and (b) V = 15 m/s, P = 81 Pa

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Fig. 6

Sound intensity against pressure at 15 m/s

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Fig. 7

Frequency spectrum at 15 m/s and 10−3 Pa

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Fig. 8

Time-frequency analysis of acoustic noise at V = 15 m/s: (a) pressure: 40 kPa and (b) pressure: 81 Pa

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Fig. 9

Sound intensity against cavitation number

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Fig. 10

Configuration of downstream conduit and location of transmission bars

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Fig. 11

Calibration points of downstream conduit

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Fig. 12

Contour maps of τ34 and τ35 (in μs): (a) τ34 and (b) τ35

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Fig. 13

Typical acoustic waves and propagation at V = 15 m/s, P = 40 kPa, σ = 0.69

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Fig. 14

Typical case of AE location calculated

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Fig. 15

Locations of AEs due to cavitation: (a) 12 m/s, (b) 15 m/s, and (c) 17 m/s




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