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Ariyoshi, Gen; Saruta, Koichi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Maeno, Koki*; Li, Y.*; Tsutsui, Kihei*
Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.1407 - 1420, 2023/08
Cavitation damage on a target vessel due to proton beam-induced pressure waves is one of the crucial issues for the pulsed neutron source using a mercury spallation target. As a mitigation technique for the damage, the helium microbubble injection into the mercury has been carried out by using a swirl bubbler in order to utilize compressibility of bubbles. Moreover, double-walled structure, which consists of an outer wall and an inner wall, has been applied as the target head structure. In this study, we aim to develop an abnormality diagnostic technology to detect the inner wall cracking, which is caused by such cavitation damage, from the outside of the target vessel. The mercury flow fields in the case with the cracking are evaluated by computational fluid dynamics analysis based on finite element method. And then, effect of the cracking on the flow field is discussed from the point of view of the flow-induced vibration and the acoustic vibration.
Naoe, Takashi; Kinoshita, Hidetaka; Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro
JAEA-Technology 2022-018, 43 Pages, 2022/08
JAEA-Technology-2022-018.pdf:7.84MB
In the liquid mercury target system for the pulsed spallation neutron source of Materials and Life science experimental Facility (MLF) at the Japan in the Japan Proton Accelerator Research Complex (J-PARC), cavitation that is generated by the high-energy proton beam-induced pressure waves, resulting severe erosion damage on the interior surface of the mercury target vessel. The erosion damage is increased with increasing the proton beam power, and has the possibility to cause the leakage of mercury by the penetrated damage and/or the fatigue failure originated from erosion pits during operation. To achieve the long term stable operation under high-power proton beam, the mitigation technologies for cavitation erosion consisting of surface modification on the vessel interior surface, helium gas microbubble injection, double-walled beam window structure has been applied. The damage on interior surface of the vessel is never observed during the beam operation. Therefore, after the target operation term ends, we have cut out specimen from the target nose of the target vessel to inspect damaged surface in detail for verification of the cavitation damage mitigation technologies and lifetime estimation. We have developed the techniques of specimen cutting out by remote handling under high-radiation environment. Cutting method was gradually updated based on experience in actual cutting for the used target vessel. In this report, techniques of specimen cutting out for the beam entrance portion of the target vessel in high-radiation environment and overview of the results of specimen cutting from actual target vessels are described.
Sasa, Toshinobu
Purazuma, Kaku Yugo Gakkai-Shi, 98(5), p.211 - 215, 2022/05
Lead-bismuth eutectic (LBE) alloy is promising as a spallation target for next-generation reactor coolants and accelerator drive systems (ADS) due to its nuclear and chemical properties. LBE is a heavy metal, and it has good properties both as a spallation target and as a coolant for nuclear transmutation systems of long-lived radioactive nuclei. On the other hand, to improve compatibility with structural materials is one of the major issues in its utilization. The latest research results such as high-temperature operation of LBE and oxygen concentration control to ensure corrosion resistance with the aim of early commercialization of nuclear conversion technology by ADS is introduced.
Obayashi, Hironari; Yamaki, Kenichi*; Yoshimoto, Hidemitsu*; Kita, Satoshi*; Wan, T.*; Sasa, Toshinobu
JAEA-Technology 2021-035, 66 Pages, 2022/03
JAEA-Technology-2021-035.pdf:4.26MB
Construction of Transmutation Experimental Facility (TEF) is under planning in Japan Proton Accelerator Research Complex (J-PARC) program to promote R&Ds on realization of transmutation technology by an accelerator driven system (ADS). As a facility of TEF, ADS Target Test Facility (TEF-T) will provide a spallation target to study target technology and perform post irradiation examination (PIE) of candidate materials of ADS. In ADS, lead-bismuth eutectic (LBE) alloy is used as a spallation target material and a core coolant. As is well known, LBE has corrosive to structural materials hence each component of the target system should provide compatibility with LBE. In addition, instrumentations for LBE are restricted by the target operation condition such as high temperature and irradiation environment. The devices for LBE have been developed individually to achieve the LBE target system. "Integrated Multi-functional MOckup for TEF-T Real-scale TArget Loop, IMMORTAL" was fabricated as a mock-up test loop of the target for the purpose of the integration testing of individually developed devices. This report describes an overview of IMMORTAL and the design of the installed devices.
Teshigawara, Makoto; Nakamura, Mitsutaka; Kinsho, Michikazu; Soyama, Kazuhiko
JAEA-Technology 2021-022, 208 Pages, 2022/02
JAEA-Technology-2021-022.pdf:14.28MB
The Materials and Life science experimental Facility (MLF) is an accelerator driven pulsed spallation neutron and muon source with a 1 MW proton beam. The construction began in 2004, and we started beam operation in 2008. Although problems such as exudation of cooling water from the target container have occurred, as of April 2021, the proton beam power has reached up to 700 kW gradually, and stable operation is being performed. In recent years, the operation experience of the rated 1 MW has been steadily accumulated. Several issues such as the durability of the target container have been revealed according to the increase in the operation time. Aiming at making a further improvement of MLF, we summarized the current status of achievements for the design values, such as accelerator technology (LINAC and RCS), neutron and muon source technology, beam transportation of these particles, detection technology, and neutron and muon instruments. Based on the analysis of the current status, we tried to extract improvement points for upgrade of MLF. Through these works, we will raise new proposals that promote the upgrade of MLF, attracting young people. We would like to lead to the further success of researchers and engineers who will lead the next generation.
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.
for a mercury target induced by 3-GeV protonsMatsuda, Hiroki; Iwamoto, Hiroki; Meigo, Shinichiro; Takeshita, Hayato*; Maekawa, Fujio
Nuclear Instruments and Methods in Physics Research B, 483, p.33 - 40, 2020/11
Times Cited Count：3 Percentile：36.4(Instruments & Instrumentation)A thick target neutron yield for a mercury target at an angle of 180 from the incident beam direction is measured with the time-of-flight method using a 3-GeV proton beam at the Japan Proton Accelerator Research Complex (J-PARC). Comparing the experimental result with a Monte Carlo particle transport simulation by the Particle and Heavy Ion Transport code System (PHITS) shows that there are apparent discrepancies. We find that this trend is consistent with an experimental result of neutron-induced re- action rates obtained using indium and niobium activation foils. Comparing proton-induced neutron-production double-differential cross-sections for a lead target at backward directions between the PHITS calculation and experimental data suggests that the dis- crepancies for our experiments would be linked to the neutron production calculation around 3 GeV by the PHITS spallation model and/or the calculation of nonelastic cross-sections around 3 GeV in the particle transport simulation.
Takada, Hiroshi; Haga, Katsuhiro
JPS Conference Proceedings (Internet), 28, p.081003_1 - 081003_7, 2020/02
At the Japan Proton Accelerator Research Complex (J-PARC), the pulsed spallation neutron source has been in operation with a redesigned mercury target vessel from October 2017 to July 2018, during which the operational beam power was restored to 500 kW and the operation with a 1-MW equivalent beam was demonstrated for one hour. The target vessel includes a gas-micro-bubbles injector and a 2-mm-wide narrow mercury flow channel at the front end as measures to suppress the cavitation damage. After the operating period, it was observed that the cavitation damage at the 3-mm-thick front end of the target vessel could be suppressed less than 17.5 
m.
Miyahara, Shinya*; Ohdaira, Naoya*; Arita, Yuji*; Maekawa, Fujio; Matsuda, Hiroki; Sasa, Toshinobu; Meigo, Shinichiro
Nuclear Engineering and Design, 352, p.110192_1 - 110192_8, 2019/10
Times Cited Count：5 Percentile：48.99(Nuclear Science & Technology)Lead-Bismuth Eutectic (LBE) is used as a spallation neutron target and coolant materials of Accelerator Driven System (ADS), and many kinds of elements are produced as spallation products. It is important to evaluate the release and transport behavior of the spallation products in the LBE. The inventories and the physicochemical composition of the spallation products produced in LBE have been investigated for an LBE loop in the ADS Target Test Facility (TEF-T) in J-PARC. The inventories of the spallation products in the LBE were estimated using the PHITS code. The physicochemical composition of the spallation products in the LBE was calculated using the Thermo-Calc code under the conditions of the operation temperatures of LBE from 350C to 500C and the oxygen concentrations in LBE from 10 ppb to 1 ppm. The calculation showed that the 5 elements of Rb, Tl, Tc, Os, Ir, Pt, Au and Hg were soluble in LBE under the all given conditions and any kinds of compound were not formed in LBE. It was suggested that the oxides of Ce, Sr, Zr and Y were stable as CeO
, SrO, ZrO and YO
in the LBE.
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：17.96(Materials Science, Multidisciplinary)The mercury target has large size as 1.3
1.32.5 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.
Wan, T.; Naoe, Takashi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Obayashi, Hironari; Sasa, Toshinobu
Materials, 12(4), p.681_1 - 681_15, 2019/02
Times Cited Count：3 Percentile：17.96(Chemistry, Physical)Wan, T.; Obayashi, Hironari; Sasa, Toshinobu
Nuclear Technology, 205(1-2), p.188 - 199, 2019/01
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)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：30.05(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.
Takada, Hiroshi
Plasma and Fusion Research (Internet), 13(Sp.1), p.2505013_1 - 2505013_8, 2018/03
The pulsed spallation neutron source of Japan Proton Accelerator Research Complex (J-PARC) has been supplying users with high intensity and sharp pulse cold neutrons using the moderators with following distinctive features; (1) 100% para-hydrogen for increasing pulse peak intensity with decreasing pulse tail, (2) cylindrical shape with 14 cm diam.12 cm long for providing high intensity neutrons to wide neutron extraction angles of 50.8, (3) neutron absorber made from Ag-In-Cd alloy to make pulse width narrower and pulse tails lower. Actually, it was measured at a low power operation that high neutron intensity of 4.510
n/cm
/s/sr could be emitted from the coupled moderator surface for 1-MW operation, and a superior resolution of 
d/d = 0.035% was achieved at a beamline (BL8) with a poisoned moderator, where d is the d-spacing of reflection. Towards the goal to achieve the target operation at 1-MW for 5000 h in a year, technical developments to mitigate cavitation damages on the target vessel with injecting gas micro-bubbles into mercury target and design improvement of target vessel structure to reducing welds and bolt connections as much as possible are under way.
Haga, Katsuhiro
Hamon, 27(4), p.155 - 158, 2017/11
The pulsed spallation neutron source driven by a high-power accelerator is one of the most powerful apparatus to provide high intensity and high quality neutrons with narrow pulse width for conducting cutting-edge researches in several domains of materials and life science. In this system, proton beams of several kW to MW order extracted from the high power accelerator is injected into a target, which is heavy metal, to generate vast amount of neutrons via the spallation reactions with the target nuclei, and slows down these neutrons to thermal to cold neutrons with a moderator and a reflector. Resultant neutron beams are then supplied to a suit of the state-of-the-art experimental devices. In this paper, mechanism to produce neutron beams and outline of the spallation neutron source, engineering design of a target system such as a mercury target, and technical topics to solve the pitting damage problem of the target vessel which is caused by the pressure wave of up to 40MPa at maximum generated in the mercury by the pulsed proton beam injection are reviewed by referring mainly to the mercury target system of the pulsed spallation neutron source at J-PARC.
Lerendegui-Marco, J.*; Cort
s-Giraldo, M. A.*; Guerrero, C.*; Harada, Hideo; Kimura, Atsushi; n_TOF Collaboration*; 114 of others*
EPJ Web of Conferences, 146, p.03030_1 - 03030_4, 2017/09
Times Cited Count：0 Percentile：0.08(Nuclear Science & Technology)Wan, T.; Obayashi, Hironari; Sasa, Toshinobu
Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 13 Pages, 2017/09
Takada, Hiroshi; Haga, Katsuhiro; Teshigawara, Makoto; Aso, Tomokazu; Meigo, Shinichiro; Kogawa, Hiroyuki; Naoe, Takashi; Wakui, Takashi; Oi, Motoki; Harada, Masahide; et al.
Quantum Beam Science (Internet), 1(2), p.8_1 - 8_26, 2017/09
At the Japan Proton Accelerator Research Complex (J-PARC), a pulsed spallation neutron source provides neutrons with high intensity and narrow pulse width to promote researches on a variety of science in the Materials and life science experimental facility. It was designed to be driven by the proton beam with an energy of 3 GeV, a power of 1 MW at a repetition rate of 25 Hz, that is world's highest power level. A mercury target and three types of liquid para-hydrogen moderators are core components of the spallation neutron source. It is still on the way towards the goal to accomplish the operation with a 1 MW proton beam. In this paper, distinctive features of the target-moderator-reflector system of the pulsed spallation neutron source are reviewed.
Sasa, Toshinobu; Saito, Shigeru; Obayashi, Hironari; Sugawara, Takanori; Wan, T.; Yamaguchi, Kazushi*; Yoshimoto, Hidemitsu
NEA/CSNI/R(2017)2 (Internet), p.111 - 116, 2017/06
Japan Atomic Energy Agency (JAEA) proposes to reduce the environmental impact caused from high-level radioactive waste by using Accelerator-driven system (ADS). To realize ADS, JAEA plans to build the Transmutation Experimental Facility (TEF) within the framework of J-PARC project. For the JAEA-proposed ADS, lead-bismuth eutectic alloy (LBE) is adopted as a coolant for subcritical core and spallation target. By using TEF in J-PARC, we are planning to solve technical difficulties for LBE utilization by completion of the data for the design of ADS. The 250kW LBE spallation target will be located in TEF facility to prepare material irradiation database. Various R&Ds for important technologies required to build the facilities are investigated such as oxygen content control, instruments development, remote handling techniques for target maintenance, and spallation target design. The large scale LBE loops for 250kW target mock up and material corrosion studies are also manufactured and ready for various experiments. The latest status of 250kW LBE spallation target optimization will be described in the presentation.
Nuclear Transmutation Division, J-PARC Center
JAEA-Technology 2017-003, 539 Pages, 2017/03
JAEA-Technology-2017-003.pdf:59.1MB
JAEA is pursuing R&D on volume reduction and mitigation of degree of harmfulness of high-level radioactive waste based on the "Strategic Energy Plan" issued in April 2014. Construction of Transmutation Experimental Facility is under planning as one of the second phase facilities in the J-PARC program to promote R&D on the transmutation technology with using accelerator driven systems (ADS). The TEF consists of two facilities: ADS Target Test Facility (TEF-T) and Transmutation Physics Experimental Facility (TEF-P). Development of spallation target technology and study on target materials are to be conducted in TEF-T with impinging a high intensity proton beam on a lead-bismuth eutectic target. Whereas in TEF-P, by introducing a proton beam to minor actinide loaded subcritical cores, physical properties of the cores are to be studied, and operation experiences are to be acquired. This report summarizes results of technical design for construction of one of two TEF facilities, TEF-T.
