ICONE23-1110 MEASUREMENT OF CAVITATION IN A DOWNSTREAM CONDUIT OF THE LIQUID LITHIUM TARGET FOR INTERNATIONAL FUSION MATERIALS IRRADIATION FACILITY

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A liquid-Li free-surface stream flowing at 15 m/s under a high vacuum of 10^<-3> Pa serves as a beam target (Li target) for the planned International Fusion Materials Irradiation Facility (IFMIF). The Engineering Validation and Engineering Design Activities (EVEDA) for the IFMIF are implemented under the Broader Approach Agreement. As a major activity of the Li target facility, the EVEDA Li test loop (ELTL) was constructed by the Japan Atomic Energy Agency. The stable Li target under the IFMIF conditions (Li temperature: 250 °C, velocity: 15 m/s, vacuum pressure: 10^<-3> Pa) has been demonstrated so far by using the ELTL. This study focuses on a cavitation-like acoustic noise that was detected in a downstream conduit where the Li target flowed under vacuum conditions. This noise was investigated using acoustic-emission 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 by the fast Fourier transform (FFT) and the continuous wavelet transform (CWT) were performed to characterize the acoustic noise. The results are as follows: 1) the acoustic noise was intermittent and consisted of multiple acoustic emissions whose time-width and frequency were 0.2 ms and less than 350 kHz respectively, and 2) the development of the acoustic noise was distinguished by four stages with regards to the change of sound intensity by using the cavitation number. From these results, we concluded that acoustic noise was generated from cavitation occurring in the downstream conduit.

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