JOPSS - Search Results

Journal Articles

Development of the high-power spallation neutron target of J-PARC

Haga, Katsuhiro; Kogawa, Hiroyuki; Naoe, Takashi; Wakui, Takashi; Wakai, Eiichi; Futakawa, Masatoshi

Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 13 Pages, 2022/03

The cross-flow type target was developed as the basic design of mercury target in J-PARC, and the design has been improved to realize the MW-class pulsed spallation neutron source. When the high-power and short-pulsed proton beam is injected into the mercury target, pressure waves are generated in mercury by rapid heat generation. The pressure waves induce the cavitation damages on the target vessel. Two countermeasures were adopted, namely, the injection of microbubbles into mercury and the double walled structure at the beam window. The bubble generator was installed in the target vessel to absorb the volume inflation of mercury and mitigate the pressure waves. Also, the double walled target vessel was designed to suppress the cavitation damage by the large velocity gradient of rapid mercury flow in the narrow channel of double wall. Finally, we could attain 1 MW beam operation with the duration time of 36.5 hours in 2020, and achieved the long term stable operation with 740 kW from April in 2021. This report shows the technical development of the high-power mercury target vessel in view of thermal hydraulics to attain 1 MW operation.

Journal Articles

Effect of proton beam profile on stress in JSNS target vessel

Kogawa, Hiroyuki; Ishikura, Shuichi*; Sato, Hiroshi; Harada, Masahide; Takatama, Shunichi*; Futakawa, Masatoshi; Haga, Katsuhiro; Hino, Ryutaro; Meigo, Shinichiro; Maekawa, Fujio; et al.

Journal of Nuclear Materials, 343(1-3), p.178 - 183, 2005/08

https://doi.org/10.1016/j.jnucmat.2004.08.032

Times Cited Count：8 Percentile：49.16(Materials Science, Multidisciplinary)

A cross-flow type (CFT) mercury target with flow guide blades, which has been developed for JSNS, can suppress the generation of stagnant flow region especially near the beam window where the peak heat density is generated due to spallation reaction. Then, a flat type beam window has been applied to the CFT target from the viewpoint of suppressing dynamic stress caused by a pressure wave, which has been estimated with a mercury model of the linear equation of state. The recent experimental results obtained by using a proton beam incidents to mercury led that a cutoff pressure model in the equation of state of mercury caused a suitable dynamic stress with experimental results. Dynamic stress analyses were carried out with the cutoff pressure model, in which the negative pressure less than 0.15 MPa was not generated. The generated dynamic stress in the flat beam window became much larger than that in a semi-cylindrical type window. However, the generated stress in the semi-cylindrical type beam window was over the allowable stress of SS316L under the peak heat density of 668 W/cc. In order to decrease the dynamic stress in the semi-cylindrical beam window, the incident proton beam was defocused to decrease the peak heat density down to 218 W/cm $^{3}$ . As a result, the dynamic stress could be suppressed less than the allowable stress. On the other hand, due to defocus of the proton beam, high heat density was generated on the end of the flow guide blades, which caused high thermal stress exceeding the allowable stress. To decrease the thermal stress, several shapes of the blade ends were studied analytically, which were selected so as not to affect the mercury flow distribution. A simple thin-end blade showed low thermal stress below the allowable stress.

Journal Articles

Water flow experiments and analyses on the cross-flow type mercury target with perforated plates

Haga, Katsuhiro; Kinoshita, Hidetaka; Kaminaga, Masanori; Hino, Ryutaro; Tagawa, Hisato*; Kukita, Yutaka*

Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 8 Pages, 2003/04

The cross-flow type mercury target, in which mercury flows crossing the proton beam path, has been developed as the spallation target of the material and life science facility in the high intensity proton accelerator project. As a part of design optimization, we proposed a mercury target using perforated plates aiming to simplify the inner structure, to make the target assembling easier, and to decrease the assembling cost. Then, the effectiveness of the target structure was investigated by no-heat water experiments and computational analyses. A mockup model of the cross-flow type mercury target using perforated plates was fabricated with plexi-glass and the water flow field was measured using PIV technique and the results were compared with the analytical results. The cross-flow field was realized by perforated plates and the analytical results corresponded well with the experimental results in the proton beam path where the cooling of heat generation is important.

Journal Articles