Fabrication of bubbler nozzle for micro-bubble injection in liquid mercury

Bucheeri, A.; Kurishita, Hiroaki*; Kato, Masahiro*; Naoe, Takashi   ; Kogawa, Hiroyuki  ; Futakawa, Masatoshi  ; Maekawa, Katsuhiro*

Mercury target system for high power spallation neutron sources is being developed. Proton beam will be injected into the target. Pressure waves will be generated and cavitation damage will be imposed on the target vessel. Injection of microbubbles may be effective to act as a cushion against pressure waves. Numerical simulations were carried out to investigate the optimum generation of microbubbles taking into account; wettability, bubbler size, gas flow rate, and liquid flowing velocity. It was found that orientation with respect to flowing liquid and bubbler geometry are essential parameters. The fabrication method uses Mo and 316L SS powders and glass fibers of 100 m in diameter. Sintering at a temperature between melting point causes glass to evaporate leaving a hole and densify the powder. Green compacts were prepared at various compressive loads and then subjected to sintering. The hole exhibited straightness and a circular cross-section, and was free from powder and glass.