(FT/P5-35) Free-Surface Fluctuation at High Speed Lithium Flow for IFMIF

H. Horiike1), H. Kondo1), H. Nakamura2), S. Miyamoto1), N. Yamaoka1), I. Matsushita3), M. Ida2), K. Ara2), T. Muroga4), H. Matsui5)
1) Osaka Univ Grad School of Engineering, Osaka, Japan
2) Japan Atomic Energy Agency, Ibaraki, Japan
3) Shinryo High Technologies, Ltd., Hyogo, Japan
4) National Institute for Fusion Science, Gifu, Japan
5) Tohoku University, Miyagi, Japan

Abstract.  An intense neutron source like IFMIF, requires very high speed, and very stable free surface lithium flow as the beam target. The experimental study of the flow target was initiated in 2002 with installing the test section to the lithium loop facility at Osaka University. The free surface test section, which is stainless steel 304 made 70 mm-width flow channel, is aligned horizontally and produces Li jet flow of 10 mm-depth at temperature of 300oC. Flow characteristic of the present loop was tested, and velocity of 15 m/s was attained under 0.1 MPa of Ar cover gas. The flow velocity in lower pressure condition is limited to a half by cavitation at the pump. Surface fluctuations, mainly caused by the waves, were measured with using a high-dynamic range ccd cameras and with scanning by an electro-contact probe along the designed beam axis. It was scanned along the perpendicular direction to the flow for the velocity range of 1-15 m/s. Frequency of the contacts were measured. It was found that the contact frequency increased with decreasing the probe height, and reached maximum near the normal thickness of 10mm. And then the frequency decreased down to 0, i.e. full contact of the needle and the liquid. The average thickness was defined as the height that the contact frequency had the maximum, and the wave amplitude as the height difference between no-contact and full-contact. The amplitude was found to grow with an increase of the velocity, and reached 2.2 mm at 15 m/s. At this velocity, however, the histogram shows that waves with larger amplitude than 1mm, which is IFMIF specification, were limited less than 10% in probability. These surface wave property was compared with the linear stability theory on a shear layer underneath the surface, and shows good agreement. Variation of the average thickness to velocity is examined from the point of view of surface wakes generated at the corners between the nozzle edge and side walls. Considering these results, engineering design of the IFMIF Li target is in progress.

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