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Tanaka, Masaaki; Ono, Ayako; Hamase, Erina; Ezure, Toshiki; Miyake, Yasuhiro*
Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai 2018 Koen Rombunshu (CD-ROM), 4 Pages, 2018/08
Decay heat removal system (DHRS) by using the natural circulation without depending on the pump as the mechanical equipment is recognized as one of the most effective methodologies for the sodium-cooled fast reactor from the viewpoint of the safety enhancement. The numerical estimation method which can predict thermal hydraulic phenomena in the natural circulation under the plant cooling process by operating the various DHRSs including the severe accident is necessarily required. In this paper, the numerical results of the preliminary analysis for the sodium experiment condition with the apparatus of PLANDTL-2, in which the core and the upper plenum with a dipped-type direct heat exchanger (DHX) were modeled, were discussed, in order to establish an appropriate numerical models for the direct heat exchanger (DHX).
Kawamura, Shunsuke; Naoe, Takashi; Ikeda, Tsubasa; Tanaka, Nobuatsu*; Futakawa, Masatoshi
no journal, ,
A target vessel enclosing mercury made of stainless steel is used for the J-PARC spallation neutron source. It is severely damaged by the pressure-wave-induced cavitation with injecting intense proton beam. The front end of the target vessel has a double-walled structure with a narrow channel was adopted to the vessel for expecting to reduce cavitation damage. Effect of cavitation damage mitigation in narrow channel has been experimentally demonstrated. However, damage mitigation mechanism is not clarified yet. As a first step of studies to understand the mechanism of cavitation damage mitigation in narrow channel, growth and collapse behaviors of the spark-induced cavitation bubbles under flow condition were observed by using a high-speed video camera. Furthermore, the wall vibration by cavitation bubble collapse was measured by parametrically changing the flow velocity. The experimental results showed that the ejection angle of the microjet ejected by bubble collapsing leaned towards flowing direction as the flow velocity increases. The wall vibration was reduced with increasing flow velocity.
Ikeda, Tsubasa; Kogawa, Hiroyuki; Naoe, Takashi; Kawamura, Shunsuke; Tanaka, Nobuatsu*; Futakawa, Masatoshi
no journal, ,
In a mercury target used for the pulsed spallation neutron source at J-PARC, pressure waves are generated by the rapid thermal expansion of mercury due to the high-intensity pulsed-proton beam bombardment. They induces cavitation, causing severe erosion damage on the mercury enclosure vessel made of stainless steel. Gas microbubbles injection into mercury is one of effective techniques to suppress the pressure. At J-PARC, a swirl-flow bubble-generator has been developed and installed in the mercury target. Increasing the gas void fraction is effective to enhance the suppression effect. In this study, dependencies of the vane angle and reduction rate of the Venturi were parametrically investigated through a water experiment in order to optimize the swirl-flow bubble-generator for decreasing the aspiration pressure without increasing pressure drop. The result showed that the gas aspiration rate of the swirl-flow bubble-generator increased as the reduction rate at the Venturi increased.
Nishimura, Satoshi*; Satake, Masaaki*; Nishi, Yoshihisa*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki; Nagatake, Taku
no journal, ,
In order to validate a spray cooling model for spent fuel pool (SFP) in the severe accident code "MAAP", benchmark analysis of SFP spray cooling tests was conducted with MAAP ver. 5.04. In a current spray cooling model in MAAP code, spray water entered into a fuel assembly flows down uniformly on the surface of fuel pins and fuel racks in the form of liquid film and cools the fuel pin from its top to the bottom. As a result, the current MAAP model causes effective cooling and leads to the tendency of overestimation of spray cooling rate comparing to the measured data.