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Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Takada, Hiroshi
Journal of Nuclear Science and Technology, 55(2), p.160 - 168, 2018/02
Times Cited Count：5 Percentile：45.59(Nuclear Science & Technology)The mercury target vessel used for the spallation neutron source in J-PARC has multi-walled structure made of stainless steel type 316L, which comprises a mercury vessel and a water shroud. In 2015, water leak incidents from the water shroud occurred while the mercury target was operated with a proton beam power of 500 kW. Several investigations were conducted to identify the cause of failure. The results of the visual inspections, mockup tests, and analytical evaluations suggested that the water leak was caused by the combination of two factors. One was the diffusion bonding failure due to the large thermal stress induced by welding of the bolt head, which fixes the mercury vessel and the water shroud, during the fabrication process. The other was the thermal fatigue failure of the seal weld due to the repetitive beam trip during the operating period. These target failures point to the importance of eliminating initial defects from welding lines and to secure the rigidity and reliability of welded structures. The next mercury target was fabricated with an improved design which adopted parts of monolithic structure machined by wire EDM to reduce welding lines, and intensified inspections to eliminate the initial defects. The operation with the improved target is planned to be started in October 2017.
Kai, Tetsuya; Harada, Masahide; Maekawa, Fujio; Teshigawara, Makoto; Konno, Chikara; Ikeda, Yujiro
Journal of Nuclear Science and Technology, 41(Suppl.4), p.172 - 175, 2004/03
In J-PARC neutron source, intense protons (3 GeV,1 MW) pass through a proton-beam window and bombard a Hg target in a target-moderator-reflector-assembly (TMRA). The SS316 target chamber is the most highly activated. Decouplers (Ag-In-Cd (AIC) alloy) are also highly activated. Some neutron extraction holes of Be and AL-coated iron reflector are lined with AIC alloy. A SS316 shield is located outer the TMRA. All these components are cooled by H
O or DO. We estimated the induced-radioactivity of the TMRA components and the cooling water using NMTC/JAM, MCNP4 and DCHAIN-SP. As results, the remote maintenance and massive shields were indispensable. For example, a 30 cm thick Fe cask for the reflector assembly was necessary to attenuate the radiation less than 1 mSv/h. The cask required a 130-ton crane. The AL-coated Fe of the reflector was adopted instead of SS316 resulting in eliminating the high activity of Ni in SS316 and reduction of the cask weight. Based on these results, shielding wall designs and maintenance scenarios of the highly activated components are developed.
Nakashima, Hiroshi; Takada, Hiroshi; Kasugai, Yoshimi; Meigo, Shinichiro; Maekawa, Fujio; Kai, Tetsuya; Konno, Chikara; Ikeda, Yujiro; Oyama, Yukio; Watanabe, Noboru; et al.
Journal of Nuclear Science and Technology, 39(Suppl.2), p.1155 - 1160, 2002/08
no abstracts in English
Haga, Katsuhiro; Terada, Atsuhiko*; Kaminaga, Masanori; Hino, Ryutaro
Nuclear Engineering and Design, 210(1-3), p.157 - 168, 2001/12
Times Cited Count：3 Percentile：27.07(Nuclear Science & Technology)The mercury target is used in the spallation neutron source driven by a high intensity proton accelerator. In this study the effectiveness of the cross-flow type mercury target structure was evaluated experimentally and analytically. Prior to the experiment, the mercury flow field and the temperature distribution in the target container were analyzed assuming the proton beam energy and power of 1.5GeV and 5MW. Then the average water flow velocity field in the target mock-up model, which was fabricated from plexiglass for a water experiment, was measured at room temperature using the PIV technique. Water flow analyses were also conducted. The experimental results showed that the cross-flow could be realized in most of the proton beam path area and the analytical result of the water flow velocity field showed good correspondence to the experimental result in the case of the Reynolds number of more than 4.83E5 at the model inlet. With these results, the effectiveness of the cross-flow type mercury target structure and the present analysis code system was demonstrated.
Kasugai, Yoshimi; Takada, Hiroshi; Meigo, Shinichiro; Maekawa, Fujio; Nakashima, Hiroshi; Ikeda, Yujiro; Ino, Takashi*; Sato, Setsuo*; Jerde, E.*; Glasgow, D.*
JAERI-Data/Code 2000-042, 62 Pages, 2001/02
JAERI-Data-Code-2000-042.pdf:1.96MB
no abstracts in English
particles by quantum molecular dynamics plus statistical decay modelMeigo, Shinichiro; Chiba, Satoshi; Shin, Kazuo*
Journal of Nuclear Science and Technology, 36(3), p.250 - 255, 1999/03
Times Cited Count：1 Percentile：13.15(Nuclear Science & Technology)no abstracts in English
Ito, Kazuhiro*; Tsuji, Yoshiyuki*; Nakamura, Hideo; Kukita, Yutaka*
9th Int. Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-9)(CD-ROM), 16 Pages, 1999/00
no abstracts in English
Nakamura, Hideo; Ito, Kazuhiro*; Kukita, Yutaka*; *; ; Maekawa, Hiroshi; Katsuta, Hiroji
Journal of Nuclear Materials, 258-263, p.440 - 445, 1998/00
Times Cited Count：7 Percentile：53.73(Materials Science, Multidisciplinary)no abstracts in English
; Nakamura, Hideo; *; Takeuchi, Hiroshi; S.Cevolani*; Martone, M.*; T.Hua*; D.Smith*; Katsuta, Hiroji
Proc. of 2nd Int. Topical Meeting on Nuclear Applications of Accelerator Technology (AccApp'98), p.541 - 547, 1998/00
no abstracts in English
Nakamura, Hideo; *; Kukita, Yutaka*; *; ; Maekawa, Hiroshi
Eighth Int. Topical Meeting on Nuclear Reactor Thermal-Hydraulics (NURETH-8), 3, p.1268 - 1275, 1997/00
no abstracts in English
H(d,n)
He neutron source by total absorption method using water bath; ; ;
Journal of Nuclear Science and Technology, 12(8), p.491 - 501, 1975/08
Times Cited Count：0no abstracts in English
Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Takada, Hiroshi
no journal, ,
The mercury target system in J-PARC is one of the most powerful neutron source in the world which operates with the pulsed proton beam of 3GeV at the pulse frequency of 25Hz. Twice in 2015, we experienced failures in the water shroud of the mercury target vessel while they were in operation with the proton beam power of 500 kW. The target vessel was made of stainless steel 316L. The first failure was the water leak out of the water shroud whose wall thickness was 3 mm, and we could find the leak location by visual inspection. Based on the cause analyses, it was assumed that part of the diffusion bonding failed due to thermal stress which was greater than the yield strength of 255 MPa by TIG welding during the fabrication process. The spare target was repaired to prevent the same trouble and installed to the target system. The second failure was the water leak into the helium layer, which was the intermediate space between the mercury vessel and the water shroud. Because the leak place was inside of the target vessel, the leak location has not identified yet. Overall, it could be said that the target failures had been resulted from conditions difficult to examine by analytical approaches at the stage of target design, e.g., those relating to the bonding/welding processes. In order to prevent such troubles, we decided the design strategies to minimize welding part in the next target design and to increase radiographic test during fabrication process.
