Speaker
Sachiko Yoshihashi
(Department of Applied Nuclear Technology)
Description
In the international fusion materials irradiation facility (IFMIF), 14 MeV neutrons are generated by 40 MeV deuteron beam injection into a high-speed liquid lithium (Li) plane jet, flowing along a vertical concave wall in vacuum. Measurement of a free surface flow and fluctuation of the thickness are required to produce a stable neutron field and maintain the safety of Li target system.In previous study, we proposed laser reflection method as new non-contact measurement of the Li surface fluctuation. The method is a technique to measure fluctuation of jet thickness from a reflection point of laser beam which represents a slope angle of fluid surface. The method can get the time variation of Li surface fluctuation in contrast to the contact probe method. The present work is intended to provide new insight into characteristics of Li surface wave from the time variation of surface fluctuation which obtained from the method.
Experiment is performed using the Li circulation loop at Osaka University. Wave characteristics are investigated from the surface fluctuation by the crest-to-trough method. The wave height and a half wave period is defined as the height and time interval between crest and trough, respectively. First, probability distribution of wave period of each Li flow velocity is calculated. As the result, it is found that short period wave increase with increasing velocity. In addition, the distribution has log-normality. It is similar to the characteristics of the previous study using the contact probe. Next, it is known that waves break when their steepness (height per wavelength) exceeds the critical steepness. The critical steepness of regular water wave is 0.14107. As the result of investigation of the relation between wave height and wavelength of this experiment, the critical steepness of Li wave is smaller than that of water wave.
Co-authors
Eiji Hoashi
(Osaka University, Osaka, Japan)
Hiroo Kondo
(Japan Atomic Energy Agency, Ibaraki, Japan)
Hiroshi Horiike
(Department of Applied Nuclear Technology, Fukui University of Technology, Fukui, Japan)
Kei Higashi
(Mitsubishi Heavy Industry, Hyogo, Japan)
Nobuo Yamaoka
(Osaka University, Osaka, Japan)
Sachiko Yoshihashi
(Department of Applied Nuclear Technology, Fukui University of Technology, Fukui, Japan)
Takafumi Okita
(Osaka University, Osaka, Japan)
Takuji Kanemura
(Japan Atomic Energy Agency, Ibaraki, Japan)
