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Naoe, Takashi; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Wakui, Takashi; Wakai, Eiichi; Haga, Katsuhiro; Takada, Hiroshi
Materials Science Forum, 1024, p.111 - 120, 2021/03
The mercury target vessel for the at the J-PARC neutron source is severely damaged by the cavitation caused by proton beam-induced pressure waves in mercury. To mitigate the cavitation damage, we adopted a double-walled structure with a narrow channel for the mercury at the beam window of the vessel. In addition, gas microbubbles were injected into the mercury to suppress the pressure waves. The front end of the vessel was cut out to inspect the effect of the damage mitigation technologies on the interior surface. The results showed that the double-walled target facing the mercury with gas microbubbles operating at 1812 MWh for an average power of 434 kW had equivalent damage to the single-walled target without microbubbles operating 1048 MWh for average power of 181 kW. The erosion depth due to cavitation in the narrow channel was clearly smaller than it was on the wall facing the bubbling mercury
Naoe, Takashi; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Wakui, Takashi; Wakai, Eiichi; Haga, Katsuhiro; Takada, Hiroshi
JPS Conference Proceedings (Internet), 28, p.081004_1 - 081004_6, 2020/02
The beam window of the mercury target vessel in J-PARC is severely damaged by the cavitation. The cavitation damage is a crucial factor to limit lifetime of the target because it increases with the beam power. Therefore, mitigating cavitation damage is an important issue to operate the target stably for long time at 1 MW. At J-PARC, to mitigate the cavitation damage: gas microbubbles are injected into mercury for suppressing pressure waves, and double-walled structure with a narrow channel of 2 mm in width to form high-speed mercury flow (4m/s) has been adopted. After operation, the beam window was cut to inspect the effect of the cavitation damage mitigation on inner wall. We optimized cutting conditions through the cold cutting tests, succeeding in cutting the target No.2 (without damage mitigation technologies) smoothly in 2017, and target No.8 with damage mitigation technologies. In the workshop, progress of cavitation damage observation for the target vessel will be presented.
Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Hanano, Kohei; Haga, Katsuhiro; Takada, Hiroshi; Shimada, Tsubasa*; Kanomata, Kenichi*
JPS Conference Proceedings (Internet), 28, p.081002_1 - 081002_6, 2020/02
A mercury target vessel of J-PRAC is designed with a triple-walled structure consisting of the mercury vessel and a double-walled water shroud with internal and external vessels. During the beam operation at 500 kW in 2015, small water leakages from a water shroud of the mercury target vessel occurred twice. Design, fabrication and inspection processes were improved based on the lessons learned from the target failures. The total length of welding lines at the front of the mercury target vessel decreases drastically to approximately 55% by adopting monolithic structure cut out from a block of stainless steel by the wire-electrical discharge machining. Thorough testing of welds by radiographic testing and ultrasonic testing was conducted. The fabrication of the mercury target vessel #8 was finished on September 2017 and the beam operation using it started. Stable beam operation at 500 kW has been achieved and it could experience the maximum beam power of 1 MW during a beam test.
Wakui, Takashi; Ishii, Hideaki*; Naoe, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Wakai, Eiichi; Takada, Hiroshi; Futakawa, Masatoshi
Materials Transactions, 60(6), p.1026 - 1033, 2019/06
Times Cited Count:3 Percentile:18.28(Materials Science, Multidisciplinary)The mercury target has large size as 1.31.32.5 m. In view of reducing the amount of wastes, we studied the structure so that the fore part could be separated. The flange is required to have high seal performance less than 110 Pa m/s. Invar with low thermal expansion is a candidate. Due to its low stiffness, however, the flange may deform when it is fastened by bolts. Practically invar is reinforced with stainless steel where all interface between them has to be bonded completely with the HIP bonding. In this study, we made specimens at four temperatures and conducted tensile tests. The specimen bonded at 973 K had little diffusion layer, and so fractured at the interface. The tensile strength reduced with increasing the temperature, and the reduced amount was about 10% at 1473 K. The analyzed residual stresses near the interface increased by 50% at maximum. Then, we concluded that the optimum temperature was 1173 K.
Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi; Shintaku, Yohei*; Li, T.*; Kanomata, Kenichi*
Choompa Techno, 30(5), p.16 - 20, 2018/10
A mercury target vessel has been used for the spallation neutron source at J-PARC. It has a complicated multi-layered structure composed of a mercury target and a surrounding double-walled water shroud, which is assembled with thin plates (minimum thickness of 3 mm) by welding. Thus, welding inspection during the manufacturing process is important. We investigated the applicability of new ultrasonic inspections using specimens (thickness of 3 mm) with defects to improve the accuracy of welding inspection for the mercury target vessel. Immersion ultrasonic testing using a probe (frequency of 50 MHz) could detect a spherical defect with a diameter of 0.2 mm. The size was smaller than target value of 0.4 mm. The length of unwelded region estimated using the phased array ultrasonic testing corresponded with the actual length (0.8 - 1.5 mm).
Naoe, Takashi; Wakui, Takashi; Kogawa, Hiroyuki; Wakai, Eiichi; Haga, Katsuhiro; Takada, Hiroshi
Advanced Experimental Mechanics, 3, p.123 - 128, 2018/08
A mercury target vessel, composed of SUS316L, is used for the pulsed neutron source and is assembled via TIG welding. While in operation, the target vessel suffers ca. 10 loading cycles with a high strain rate of ca. 50 s because of the proton-beam-induced pressure waves in mercury. The gigacycle fatigue strength for solution annealed SUS316L stainless steels and its welded specimens were investigated through ultrasonic fatigue tests. The experimental results showed that an obvious fatigue limit was not observed at fewer than 10 cycles for the base metal. In the case of no weld defects observed via penetration tests, the fatigue strength of the removed-weld-bead specimen, in which the weld lines were arranged at the center of the specimen, appeared to be slightly higher than that of the base metal. By contrast, as-welded specimens with the weld bead intact showed apparent degradation of the fatigue strength owing to the stress concentration around the weld toe.
Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Shintaku, Yohei*; Li, T.*; Murakami, Kazuya*; Kanomata, Kenichi*; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi; et al.
Journal of Nuclear Materials, 506, p.3 - 11, 2018/08
Times Cited Count:3 Percentile:30.45(Materials Science, Multidisciplinary)The mercury target vessel is designed as multi-walled structure with thin wall (min. 3 mm), and assembled by welding. In order to estimate the structural integrity of the vessel, it is important to measure the defects in welding accurately. For nondestructive tests of the welding, radiographic testing is applicable but it is difficult to detect for some defect shapes. Therefore it is effective to do ultrasonic testing together with it. Because ultrasonic methods prescribed in JIS inspect on the plate with more than 6 mm in thickness, these methods couldn't be applied as the inspection on the vessel with thin walls. In order to develop effective method, we carried out measurements using some testing method on samples with small defect whose size is specified. In the case of the latest phased array method, measured value agreed with actual size. It was found that this method was applicable to detect defects in the thin-walled structure for which accurate inspection was difficult so far.
Shigyo, Nobuhiro*; Uozumi, Yusuke*; Uehara, Haruhiko*; Nishizawa, Tomoya*; Hirabayashi, Keiichi*; Satoh, Daiki; Sanami, Toshiya*; Koba, Yusuke*; Takada, Masashi*; Matsufuji, Naruhiro*
Progress in Nuclear Science and Technology (Internet), 4, p.709 - 712, 2014/04
Heavy ion cancer therapy has been increased by reason of its clinical advantages. During the treatment, the secondary particles such as neutron and -ray are produced by nuclear reactions of a heavy ion incidence on a nucleus in a patient body. Estimation of the secondary neutrons yields data is essential for assessment of radiation safety on both of workers and public in treatment facilities. Neutron energy spectra from a water phantom simulating the patient body were obtained at GSI only for forward directions. We measured the neutron yields from carbon ion incident on a water phantom in wide angular range from 15 to 90 with the therapeutic ion energy.
Uozumi, Yusuke*; Shigyo, Nobuhiro*; Kajimoto, Tsuyoshi*; Hirabayashi, Keiichi*; Uehara, Haruhiko*; Nishizawa, Tomoya*; Satoh, Daiki; Sanami, Toshiya*; Koba, Yusuke*; Takada, Masashi*; et al.
HIMAC-138, p.237 - 238, 2012/08
In the heavy-ion radiotherapy, considerable discussion has been attracted regarding the potential for second cancer induction by secondary neutrons produced from the primary heavy-ion fragmentation. It is important to measure energy-angle double-differential cross sections (DDXs) of neutron- and photon-productions in heavy-ion nuclear reactions. Since it is notoriously hard to measure the spectral cross sections of neutrons in an energy range of around 1 MeV where the RBE value reaches at its maximum. In the project by last year, experiments were carried out at the synchrotron HIMAC of NIRS, Japan. The beams were C and O of 290 MeV/u and bombarded a carbon target. In measurements of neutrons and photons were used liquid scintillator detectors of 5" and 2". We have succeeded to lower the neutron energy threshold down to 0.6 MeV. The present results for neutron productions are in reasonable agreements with PHITS. Since our goal in technical aspects has been fulfilled, measurements will be continued for other reactions.
Wakai, Eiichi; Nogami, Shuhei*; Kasada, Ryuta*; Ito, Yuzuru*; Takada, Fumiki; 6 of others*
Journal of Nuclear Materials, 417, p.1325 - 1330, 2011/10
Times Cited Count:25 Percentile:86.63(Materials Science, Multidisciplinary)Takahashi, Eiichi*; Kato, Susumu*; Furutani, Hirohide*; Sasaki, Akira; Kishimoto, Yasuaki*; Takada, Kenji*; Matsumura, Satoshi*; Sasaki, Hiroyasu*
Journal of Physics D; Applied Physics, 44(30), p.302001_1 - 302001_4, 2011/08
Times Cited Count:7 Percentile:31.34(Physics, Applied)A recently developed ultrafast camera that can acquire frames per second was used to investigate positive streamer discharge. It enabled single-shot evaluation of streamer evolution without the need to consider shot-to-shot reproducibility. This camera was used to investigate streamers in argon. Growing branches, the transition when a streamer forms a return stroke, and related phenomena were clearly observed.
Wakai, Eiichi; Ando, Masami; Sawai, Tomotsugu; Tanigawa, Hiroyasu; Taguchi, Tomitsugu; Stroller, R. E.*; Yamamoto, Toshio; Kato, Yoshiaki; Takada, Fumiki
Journal of Nuclear Materials, 367-370(1), p.74 - 80, 2007/08
Times Cited Count:9 Percentile:58.28(Materials Science, Multidisciplinary)no abstracts in English
Wakai, Eiichi; Otsuka, Hideo*; Matsukawa, Shingo; Furuya, Kazuyuki*; Tanigawa, Hiroyasu; Oka, Keiichiro*; Onuki, Somei*; Yamamoto, Toshio*; Takada, Fumiki; Jitsukawa, Shiro
Fusion Engineering and Design, 81(8-14), p.1077 - 1084, 2006/02
Times Cited Count:11 Percentile:60.35(Nuclear Science & Technology)no abstracts in English
Wakai, Eiichi; Jitsukawa, Shiro; Tomita, Hideki*; Furuya, Kazuyuki; Sato, Michitaka*; Oka, Keiichiro*; Tanaka, Teruyuki*; Takada, Fumiki; Yamamoto, Toshio*; Kato, Yoshiaki; et al.
Journal of Nuclear Materials, 343(1-3), p.285 - 296, 2005/08
Times Cited Count:48 Percentile:93.9(Materials Science, Multidisciplinary)The dependence of helium production on radiation-hardening and -embrittlement has been examined in a reduced-activation martensitic F82H steel doped with B, B and B+B irradiated at 250C to 2.2 dpa. The total amounts of doping boron were about 60 massppm. The range of He concentration produced in the specimens was from about 5 to about 300 appm. Tensile and fracture toughness tests were performed after neutron irradiation. 50 MeV-He irradiation was also performed to implant about 85 appm He atoms at 120C by AVF cyclotron to 0.03 dpa, and small punch testing was performed to obtain DBTT. Radiation-hardening of the neutron-irradiated specimens increased slightly with increasing He production. The 100 MPam DBTT for the F82H+B, F82H+B+B, and F82H+B were 40, 110, and 155C, respectively. The shifts of DBTT due to He production were evaluated as about 70C by 150 appmHe and 115C by 300 appmHe. The DBTT shift in the small punch testing was evaluated as 50C.
Wakai, Eiichi; Taguchi, Tomitsugu; Yamamoto, Toshio*; Tomita, Hideki*; Takada, Fumiki; Jitsukawa, Shiro
Materials Transactions, 46(3), p.481 - 486, 2005/03
Times Cited Count:7 Percentile:51.72(Materials Science, Multidisciplinary)no abstracts in English
Wakai, Eiichi; Taguchi, Tomitsugu; Yamamoto, Toshio*; Kato, Yoshiaki; Takada, Fumiki
Materials Transactions, 45(8), p.2638 - 2640, 2004/08
Times Cited Count:1 Percentile:12.47(Materials Science, Multidisciplinary)no abstracts in English
Wakai, Eiichi; Matsukawa, Shingo; Yamamoto, Toshio*; Kato, Yoshiaki; Takada, Fumiki; Sugimoto, Masayoshi; Jitsukawa, Shiro
Materials Transactions, 45(8), p.2641 - 2643, 2004/08
Times Cited Count:6 Percentile:41.18(Materials Science, Multidisciplinary)no abstracts in English
Inoue, Tomio*; Hayakawa, Kazushige*; Shiotari, Harutaka*; Takada, Eiichi*; Torikoshi, Masami*; Nagasawa, Kiyoshi*; Hagiwara, Kazuo*; Yanagisawa, Kazuaki
Journal of Nuclear Science and Technology, 39(10), p.1114 - 1119, 2002/10
Times Cited Count:4 Percentile:29.29(Nuclear Science & Technology)no abstracts in English
Takehisa, Masaaki*; Tagawa, Seiichi*; Kashiwagi, Masayuki*; Tominaga, Hiroshi*; Ishikawa, Isamu*; Ooka, Norikazu; Kamada, Toshimitsu*; Hosobuchi, Kazunari*; Makuuchi, Keizo; Takeshita, Hidefumi; et al.
Genshiryoku Riyo No Keizai Kibo; NSA/Commentaries, No.9, 139 Pages, 2001/01
no abstracts in English
Takada, Junichi; Koike, Tadao; Tsukamoto, Michio; Nishio, Gunji; Kitani, Susumu*; Uno, Seiichiro; ; Watanabe, Hironori; Hashimoto, Kazuichiro
JAERI-M 92-048, 332 Pages, 1992/03
no abstracts in English