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Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Hanano, Kohei*; Haga, Katsuhiro; Shimada, Tsubasa*; Kanomata, Kenichi*
Materials Science Forum, 1024, p.145 - 150, 2021/03
To realize a high beam power operation at the J-PARC, a mercury target vessel covered with water shroud was developed. In the first step, to realize an operation at 500 kW, the basic structure of the initial design was followed and the connection method between the mercury vessel and the water shroud was changed. Additionally, the operation at a beam power of 500 kW was realized in approximately eight months. In the second step, to realize the operation at 1 MW, the new structure in which only rear ends of vessels were connected was investigated. Cooling of the mercury vessel is used to reduce thermal stress and thick vessels of the water shroud are used to increase stiffness for the internal pressure; therefore, it was adopted. The stress in each vessel was lower than the allowable stress based on the pressure vessel code criteria prescribed in the Japan Industrial Standard, and confirmation was obtained that the operation with a beam power of 1 MW could be conducted.
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.
Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; Hanano, Kohei; Futakawa, Masatoshi
FAPIG, (177), p.12 - 17, 2008/07
The construction of the mercury target system which is the 1MW class spallation neutron source under the J-PARC project has been completed. The mercury target system consists of the mercury target vessel, the mercury circulation system and the target trolley. The outline of the spallation neutron source in the material and life science experimental facility, and the mercury target system is reported. Several topics appeared in the course of the system fabrication and assembling are also reported. For the target vessel, the residual stress at the beam window was evaluated, and it was confirmed that the stress level is low and no problem. For the mercury pump, the outer shape and the structure of the mechanical PM pump which was newly developed and its operational results are reported. For the target trolley, the characteristic structure where all of the mercury related devices are mounted on the single trolley is reported.
Wakui, Takashi; Hanano, Kohei; Kogawa, Hiroyuki; Haga, Katsuhiro; Futakawa, Masatoshi
no journal, ,
The high power mercury target for the spallation neutron source is being developed for JSNS. The pulsed proton beams create pressure waves by thermal shock in the mercury. The pressure waves cause stress transients in the mercury vessel and pitting damage on the contact surface with the mercury. The pitting damage on the surface of the mercury vessel influences the fatigue life. The lifetime estimation of the mercury target vessel that suffers pitting damage and repeated stress simultaneously is carried out taking account into account of fatigue crack propagation from multi pits. Probability of fatigue failure in JSNS mercury vessel increased with an increase of the operation time, and was estimated to be ca 0.999 for 2500 hours operation. When failure probability of 0.1 was assumed, the lifetime of the JSNS mercury target was about 270 hours at 1 MW.
-ray analysis and behavior of spallation products produced in mercury of the neutron source at J-PARCKai, Tetsuya; Kasugai, Yoshimi; Oi, Motoki; Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Hanano, Kohei
no journal, ,
The authors sampled mercury (
120 g) and the adhesive substances (black powder) from a mercury circulation system in MLF/J-PARC. Twelve nuclides, 
Hg, 
Pt, 
Ir, Ir, 
Os, 
Hf, 
Lu, 
Lu, 
Eu, 
Sn, 
Ag, 
Y, were identified in the mercury specimen. The amounts of radioactivity were in the range between several to around hundred percents relative to calculation. Only Ag was not found in the adhesive substances. It is expected that other elements than mercury take important role to behavior of the spallation products since the content ratios of the elements were calculated to be in the order of ppb, and the elements (tin and europium) having higher solubility than silver were found in both specimens. For example, iron, which is expected to be a dominant impurity (caused by erosion of stainless steel pipes), dose not react with silver. On the other hand, iron reacts with tin.
Haga, Katsuhiro; Wakui, Takashi; Naoe, Takashi; Kogawa, Hiroyuki; Kinoshita, Hidetaka; Teshigawara, Makoto; Kasugai, Yoshimi; Seki, Masakazu; Hanano, Kohei; Suzuki, Toru; et al.
no journal, ,
Pitting damage of the target vessel wall is the crucial issue for the development of the high power mercury target. The damage is affected by the target vessel structure and the proton beam condition. In order to improve the evaluation accuracy of the pitting depth, the data of the pitting damage in the J-PARC mercury target was indispensable. Because the first target vessel of J-PARC was damaged by the earthquake, the preparations for cutting out specimens were carried out in advance. The surface dose rate is more than 10micro Sv/h. Then, we developed the cutting machine using hole saw, and we succeeded in cutting out specimens of the outer diameter of 50 mm. A spot which seems the cavitation damage was found by visual observation. The target replacement was also successfully finished. The radioactive gas release was more than the expectation, and it roused the necessity of reconsider the off-gas treatment system.
Kogawa, Hiroyuki; Haga, Katsuhiro; Naoe, Takashi; Hanano, Kohei; Wakui, Takashi; Futakawa, Masatoshi; Takada, Hiroshi
no journal, ,
no abstracts in English
Wakai, Eiichi; Wakui, Takashi; Kogawa, Hiroyuki; Naoe, Takashi; Shoji, Masayuki; Ishikawa, Kazuyoshi; Yasu, Kazumi*; Teshigawara, Makoto; Hanano, Kohei; Narui, Norio; et al.
no journal, ,
no abstracts in English
Wakai, Eiichi; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Guan, W.; Hanano, Kohei*; Kinoshita, Hidetaka; Narui, Norio*; Haga, Katsuhiro; Teshigawara, Makoto; et al.
no journal, ,
no abstracts in English
