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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; 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).
Haga, Katsuhiro; Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Takada, Hiroshi
no journal, ,
In 2015, we experienced failure in the water shroud of the mercury target vessel while they were in operation with the proton beam power of 500 kW, and since then investigations for the failure cause were carried out. As a result, it revealed that the target failures had been resulted from conditions which were 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 and to improve the reliability and soundness of the target vessel, we decided the design strategies to minimize welding part by using wire EDM and to increase radiographic and ultrasonic test during fabrication process. For the front part of the target vessel where the heat density by proton injection is high, the mercury vessel and the water shroud will be cut out from a block of stainless steel. The components of the rear part will also be decreased and total welding length will be reduced by 70 %.
Harada, Masahide; Uchida, Toshitsugu; Sekijima, Mitsuaki; Haga, Katsuhiro; Kogawa, Hiroyuki; Kinoshita, Hidetaka; Takada, Hiroshi; Sato, Koichi; Masuyama, Koichi
no journal, ,
no abstracts in English
Wakai, Eiichi; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Haga, Katsuhiro; Guan, W.; Takada, Hiroshi; Futakawa, Masatoshi
no journal, ,
no abstracts in English
Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Haga, Katsuhiro; Takada, Hiroshi
no journal, ,
The mercury target vessel at J-PARC is designed as multi-walled structure with thin wall (min. 3 mm), and assembled by welding. To prevent recurrence of the leakage of a small amount of coolant water from the weld of the water shroud during the proton beam operation at ca. 500 kW in 2015, improvements to reduce the number of the weld in the front part and strengthen the weld inspection were conducted in the new vessel. The mercury vessel and water shroud were cut out from a block using wire discharge machining to achieve the monolithic structure and the total length of the welding line is reduced by half. The welding procedure was reconsidered to reduce the welding deformation. Radiographic and ultrasonic tests were added to the weld inspection. In particular, immersion ultrasonic was applied and the defect detection accuracy was raised to 0.2mm to improve the accuracy of the inspection of the thin wall part. The integrity of the new vessel was confirmed by its weld inspection.
Wakai, Eiichi; Naoe, Takashi; Wakui, Takashi; Harada, Masahide; Kogawa, Hiroyuki; Guan, W.; Haga, Katsuhiro; Takada, Hiroshi
no journal, ,
no abstracts in English
Harada, Masahide; Kogawa, Hiroyuki; Naoe, Takashi; Wakui, Takashi; Haga, Katsuhiro; Meigo, Shinichiro; Oi, Motoki; Takada, Hiroshi
no journal, ,
no abstracts in English
Kogawa, Hiroyuki; Naoe, Takashi; Wakui, Takashi; Haga, Katsuhiro; Harada, Masahide; Meigo, Shinichiro; Oi, Motoki; Takada, Hiroshi
no journal, ,
In the Material and Life science Facility (MLF) at J-PARC, proton beams (3 GeV, 1 MW) are injected into mercury target to generate neutron beams which are produced to the neutron experiment apparatus. Variation of shape and/or injection position of the proton beam affects structural integrity of a mercury target vessel and amount of generated neutrons. Therefore, effects of shape and injection position of the proton beam on the structural integrity and the amount of generated neutrons were investigated by both of measurement and numerical simulation. In this study, temperatures were measured on the real mercury target vessels, the heat deposition obtained in the simulation were validated and thermal stress generated in the mercury target vessel due to the heat deposition were simulated from the viewpoint of structural integrity of the mercury target vessel. Since the injected position of proton beam to the center of mercury target vessel is restricted within 6 mm in design, thermal stress simulation in this case was carried out and the maximum thermal stress became 10% larger than that in the case that proton beam injects into the center of the target. This result supports that margin of 20% in the stress assessment is suitable.
Wakui, Takashi; Saito, Shigeru; Yamasaki, Kazuhiko*; Sakai, Tomoki*; Mori, Kotaro*; Futakawa, Masatoshi
no journal, ,
Irradiation damage due to protons and neutrons reduces ductility in the mercury target vessel of J-PARC. The radiation damage is one of the factors that determine the lifetime. The evaluation of the irradiation damage is extremely important for long-term operation at high beam power. A simple and rapid indentation technique is investigated in order to evaluate mechanical properties. Ion irradiation is a technique for simulating radiation damage, but the damage area is limited to the very surface layer. Therefore, we propose a mechanical property evaluation technique using an inverse analysis combining a Kalman filter and numerical experiments to the load-depth curve. As a result, changes in the mechanical properties due to ion irradiation were detected and it was confirmed that this evaluation technique was very effectiveness. In addition, the technique was applied to lead glass, and it was clarified that the microplastic behavior of glasses can be evaluated quantitatively.
猿田 晃一; 直江 崇; 勅使河原 誠; 二川 正敏; 梁 輝
Erkan Nejdet*
JP, 2021-188317 
Patent licensing information
【課題】加工により発生するヒュームの大気中への拡散防止およご前記ヒュームを回収可能な加工装置を提供すること。 【解決手段】 加工対象物10の局所部16を溶融するために、前記局所部16を加熱する加熱ヘッド122を備えた加熱装置120と、前記局所部16と前記加熱ヘッド122とを繋ぐ加熱エリア20の外側にミストカバー層40を形成するミスト層形成装置140と、液体からミスト41を生成して前記ミスト層形成装置140に供給するミスト生成装置130と、前記加熱ヘッド122により加熱されて溶融する前記局所部16を前記加工対象物10の加工場所12に沿って移動させる加工位置移動機構30と、を備え、前記ミスト層形成装置140から噴霧された前記ミスト41により、前記加熱エリア20の外周を覆う前記ミストカバー層40を形成した、ことを特徴とする加工装置。
