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Journal Articles

Behavior of tritium release from a stainless vessel of the mercury target as a spallation neutron source

Kasugai, Yoshimi; Sato, Koichi; Takahashi, Kazutoshi*; Miyamoto, Yukihiro; Kai, Tetsuya; Harada, Masahide; Haga, Katsuhiro; Takada, Hiroshi

JPS Conference Proceedings (Internet), 33, p.011144_1 - 011144_6, 2021/03

A spallation neutron source with a mercury target has been in operation at the Materials and Life Science Experimental Facility of J-PARC since 2008. The target vessel made of stainless steel is required to be exchanged periodically due to radiation damage etc. In this presentation, tritium gas release observed in the first series of exchange work in 2011 and the analytical results will be shown.

Journal Articles

Unified mercury radioactivity monitoring system at J-PARC and its operation experiences

Harada, Masahide; Sekijima, Mitsuaki*; Morikawa, Noriyuki*; Masuda, Shiho; Kinoshita, Hidetaka; Sakai, Kenji; Kai, Tetsuya; Kasugai, Yoshimi; Muto, Giichi*; Suzuki, Akio*; et al.

JPS Conference Proceedings (Internet), 33, p.011099_1 - 011099_6, 2021/03

In MLF at J-PARC, a unified mercury radioactivity monitor (UHAM) is installed to find an indication of failure of the mercury target and loop system by detecting radioactive materials leaked from the system with a $$gamma$$-ray energy analysis with Germanium semi-conductor detectors (Ge detectors). It is composed of three units of sampling port and radiation monitors: (1) HAM for interstitial helium gas layer between the mercury vessel and surrounding water shroud of the mercury target, (2) CAM for atmosphere in the hot cell where the target loop is operated and (3) VAM for helium gas in the helium vessel where the target vessel is installed. Once any leakages of radioactive materials are detected, an alarm signal is issued immediately to the accelerator control system to stop beam operation. Software and hardware have been upgraded yearly. For example, two Ge detectors are used for HAM for redundancy, NaI Scintillation detectors are also used as supplemental for the Ge detector to keep availability of the system for high counting rate event. In April 2015, the UHAM activated when a small water coolant leakage from the water shroud of the mercury target occurred. VAM detected an abnormal increase of the counting rate in the helium vessel. It was also indicated that the measured radioactive nuclides were generated from the activation of the coolant (water) in the water shroud and not from the mercury.

Journal Articles

Off-gas processing system operations for mercury target vessel replacement at J-PARC

Kai, Tetsuya; Uchida, Toshitsugu; Kinoshita, Hidetaka; Seki, Masakazu; Oi, Motoki; Wakui, Takashi; Haga, Katsuhiro; Kasugai, Yoshimi; Takada, Hiroshi

Journal of Physics; Conference Series, 1021(1), p.012042_1 - 012042_4, 2018/06

 Times Cited Count:0 Percentile:0.11

JAEA Reports

Measurement of high-energy neutron fluxes and spectra around the J-PARC mercury spallation neutron target using multi-foil activation method

Kasugai, Yoshimi; Harada, Masahide; Kai, Tetsuya; Oi, Motoki; Meigo, Shinichiro; Maekawa, Fujio

JAEA-Data/Code 2015-033, 28 Pages, 2016/03

JAEA-Data-Code-2015-033.pdf:1.78MB

The high-energy neutron fluxes and spectra around the mercury spallation neutron source at MLF of J-PARC were measured by the multi-foil activation method. The threshold energies of neutron reactions utilized in this experiment covered from 0.1 to 50 MeV. The foil irradiation was carried out on the first beam-run of MLF from May 30th to 31th, 2008. After the irradiation, the induced radioactivity of each foil was measured using an HPGe detector, and the neutron-induced reaction-rate distribution around the mercury target was determined. Using these data, the high-energy neutron fluxes and spectra were deduced with unfolding method in which the neutron spectra calculated with PHITS code were used as the initial-guess spectra. By comparison between the initial and the unfolded spectra, it was shown that most of the calculation results, which had been the basis of the neutronics design of the MLF target assembly, were consistent with the experimental data within $$pm$$30%.

Journal Articles

R&D of invar duct for fabrication of 2nd JSNS moderators

Harada, Masahide; Teshigawara, Makoto; Maekawa, Fujio; Oi, Motoki; Kasugai, Yoshimi; Takada, Hiroshi

Journal of Nuclear Materials, 450(1-3), p.104 - 109, 2014/07

 Times Cited Count:1 Percentile:8.95(Materials Science, Multidisciplinary)

Japan Spallation Neutron Source (JSNS) in Japan Proton Accelerator Research Complex (J-PARC) has three super-critical hydrogen moderators. The moderator piping has a multilayer structure; a cryogenic layer, a vacuum layer, a helium layer and a cooling water layer. Through the fabrication of the current (1st) moderators, we learned that thermal shrinkage between room temperature (R.T.) and cryogenic temperature at the cryogenic layer made the fabrication process very difficult. Therefore, for the spare (2nd) moderators, we proposed to use a low thermal shrinkage material, Invar, as a piping material. However, there were items to be solved for realizing the Invar duct inview of the fabrication. In this presentation, we report results of (1) Bending test, (2) Welding test and (3) Dissimilar joint test on the Invar duct. (1) In the bending test, the Invar ducts of 22 mm in diameter and 1.5 mm in thickness were tried to be bent into an elbow with 40 mm in radius. By pre-cooling the duct in the liquid nitrogen followed by the bending with slow speed (1 minute), the duct could be bent without any cracks. (2) Through some welding testes by TIG-welding, the proper groove geometry was determined. (3) For the dissimilar joint test, tensile specimens including a bonding region having size of 4 or 6 mm in diameter at the smallest part and 60 mm in length were cut from three rods made by Invar-A6061 and Invar-SS316L, respectively. Those rods were bonded by the friction welding. All specimens were examined at two temperatures, R.T. and 77 K (liquid nitrogen temperature), resulting that 0.2% proof stresses corresponding to the bonding strengths were larger than those of base materials for both the Invar-A6061 and the Invar-SS316L cases. The present result indicates that the Invar duct is available for the 2nd moderators.

Journal Articles

Development of Au-In-Cd decoupler by a Hot Isostatic Pressing (HIP) technique for short pulsed spallation neutron source

Oi, Motoki; Teshigawara, Makoto; Harada, Masahide; Naoe, Takashi; Maekawa, Fujio; Kasugai, Yoshimi

Journal of Nuclear Materials, 450(1-3), p.117 - 122, 2014/07

 Times Cited Count:3 Percentile:24.02(Materials Science, Multidisciplinary)

In order to utilize Au-In-Cd alloy as a decoupler, it is required to bond between the Au-In-Cd alloy and aluminum alloy with enough bonding strength (more than 30 MPa). We adopted a Hot Isostatic Pressing (HIP) technique to realize bonding between Au-In-Cd and aluminum alloy, because it is available for curved shape of moderator vessel. As a HIP conditions of the temperature of 535 $$^{circ}$$C, pressure of 100 MPa and holding time of 1 hour, we got enough tensile strength of the bonding surface (86.6 MPa). It is larger than the required strength of 30 MPa.

Journal Articles

Recent progress of pulsed spallation neutron source in J-PARC

Takada, Hiroshi; Haga, Katsuhiro; Meigo, Shinichiro; Tatsumoto, Hideki; Kasugai, Yoshimi; Futakawa, Masatoshi

Proceedings of 11th International Topical Meeting on Nuclear Applications of Accelerators (AccApp '13), p.154 - 158, 2014/05

Remarkable progresses were achieved at a pulsed spallation neutron source in J-PARC. One is to mitigate high-pressure waves which are generated in a mercury target and a source of serious damage on the wall of target vessel by injecting gas micro-bubbles into mercury. It was confirmed with a novel in-situ diagnostic system using a laser Doppler vibrometer that the pressure waves were certainly attenuated with the gas micro-bubbles. Secondly, the supercritical cryogenic hydrogen system has been improved to remove impurity remained in the helium circulation loop by installing a purification system. As a result, the pressure drop at the heat exchanger was suppressed successfully down to several kPa even after operating for 95 days. Furthermore, we have succeeded in sampling hydrogen gas from the cryogenic hydrogen loop during operation and verified with a Raman spectroscopy that the para-hydrogen fraction was 100%, proving the neutronic performance at the moderator is kept unchanged.

Journal Articles

Experiences on radioactivity handling for mercury target system in MLF/J-PARC

Kai, Tetsuya; Kasugai, Yoshimi; Oi, Motoki; Kogawa, Hiroyuki; Haga, Katsuhiro; Kinoshita, Hidetaka; Seki, Masakazu; Harada, Masahide

Progress in Nuclear Science and Technology (Internet), 4, p.380 - 383, 2014/04

Neutrons are produced by an intense proton beam (1 MW) irradiation on a mercury target in the Material and Life science experimental Facility of J-PARC. The proton beam irradiation produces various kinds of radioactivity via the spallation reaction of mercury. Design of radioactivity treatment was carried out based on estimation by using particle transport calculation codes NMTC/JAM, MCNP/4C and an induced radioactivity calculation code DCHAIN-SP 2001. This presentation shows how the estimation being utilized in design of a mercury circulation system and an off-gas processing system as specific examples. In addition the authors report some knowledge mainly about behavior of xenon and tritium obtained in operation. This presentation includes important lessons about treatment of spallation products. Thus the lessons are expected to be fully utilized in discussions of future accelerator driven neutron sources and transmutation systems using liquid metal as target material.

Journal Articles

Activation detector measurements at the hadron absorber of the NuMI neutrino beamline at Fermilab

Matsuda, Norihiro; Kasugai, Yoshimi; Matsumura, Hiroshi*; Iwase, Hiroshi*; Toyoda, Akihiro*; Yashima, Hiroshi*; Sekimoto, Shun*; Oishi, Koji*; Sakamoto, Yukio*; Nakashima, Hiroshi; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.337 - 340, 2014/04

The Neutrinos at the Main Injector (NuMI) at Fermilab produces intense neutrino beam to investigate the phenomena of the neutrino mixing and oscillation. The Hadron Absorber, consists of thick blocks of aluminum, iron and concrete, is placed at the end of decay volume as a dump for primary proton and secondary particles generated in NuMI. In order to estimate the shielding effect, the reaction rate measurements with activation detector were carried out on the back surface of the absorber. The induced activities in the detectors were measured by analyzing their $$gamma$$-ray spectra using HPGe detectors. Two kind of peak was showed on two-dimensional distributions of obtained reaction rates at right angle to the beam direction. One was strong peaks at the both horizontal side. And, another smaller was at the top. It was concluded that these peaks were the results of particles streaming through the gaps in the Hadron Absorber shielding.

Journal Articles

Fitting method for spectrum deduction in high-energy neutron field induced by GeV-protons using experimental reaction-rate data

Kasugai, Yoshimi; Matsuda, Norihiro; Sakamoto, Yukio; Nakashima, Hiroshi; Yashima, Hiroshi*; Matsumura, Hiroshi*; Iwase, Hiroshi*; Hirayama, Hideo*; Mokhov, N.*; Leveling, A.*; et al.

Reactor Dosimetry; 14th International Symposium (ASTM STP 1550), p.675 - 689, 2012/08

Under the collaborative study project of JASMIN, shielding experiments has been carried out using the anti-proton target station (Pbar) of Fermilab. In the experiment, the multi-foil activation technique was utilized, and the neutron spectra in high-energy region between 1 and 100 MeV were deduced by using the "fitting method", which is newly developed. In this method, we made an assumption that neutron energy spectra could be expressed with a simple function. The validity of the fitting method was confirmed by comparison with the results of the unfolding method and the theoretical calculations. Finally, it was found that there are simple correlations between reaction rates and the adjusting parameters in the fitting function. The correlations are useful for estimating the adjusting parameters easily, and a neutron spectrum in the high-energy region can be deduced from a set of reaction-rate data without the complicated calculations of unfolding.

JAEA Reports

Result of study on storage plan for irradiated components generated at MLF in J-PARC

Kinoshita, Hidetaka; Wakui, Takashi; Matsui, Hiroki; Maekawa, Fujio; Kasugai, Yoshimi; Haga, Katsuhiro; Teshigawara, Makoto; Meigo, Shinichiro; Seki, Masakazu; Sakamoto, Shinichi; et al.

JAEA-Technology 2011-040, 154 Pages, 2012/03

JAEA-Technology-2011-040.pdf:8.08MB

In the MLF, relatively high level irradiated components will be generated. Therefore, these components can not be kept in standard facilities. For the irradiated components at the MLF, the storage plan using the facilities in the Nuclear Science Research Institute has been studied, but the concrete plan is not decided yet. In this report, outline of the components, prehistory of the studying for storage, schedule of the component generation and status of the possible facility, which is a hot laboratory, are described. Resulting from the comparison between the generation schedule and the plan of the hot laboratory, the difference is very large. Present status of the hot laboratory and the cost estimation of the modification to use for storage of the MLF components were studied. Using the hot laboratory seems not to have advantage from the view point of cost and modification method. Therefore, the study on a new storage facility construction will be started as soon as possible.

JAEA Reports

Influence of Great East Japan Earthquake on neutron source station in J-PARC

Sakai, Kenji; Sakamoto, Shinichi; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Kasugai, Yoshimi; Tatsumoto, Hideki; et al.

JAEA-Technology 2011-039, 121 Pages, 2012/03

JAEA-Technology-2011-039.pdf:10.87MB

This report investigates the behavior, damage and restoration of a neutron source station of the MLF at the Great East Japan Earthquake and verified the safety design for emergency accidents in the neutron source station. In the MLF, after an occurrence of the Earthquake, strong quakes were detected at the instruments, the external power supply was lost, all of the circulators shut down automatically, and the hydrogen gas was released. The leakages of mercury, hydrogen and radio-activation gases did not occur. While, the quakes made gaps between the shield blocks and ruptured external pipe lines by subsidence around the building. But significant damages to the components were not found though the pressure drop of compressed air lines influenced on a target trolley lock system and so on. These results substantiated the validity of the safety design for emergency accidents in the source station, and suggested several points of improvement.

Journal Articles

Influence of Great East Japan Earthquake on neutron target station in J-PARC

Sakai, Kenji; Futakawa, Masatoshi; Takada, Hiroshi; Sakamoto, Shinichi; Maekawa, Fujio; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; et al.

Proceedings of 20th Meeting of the International Collaboration on Advanced Neutron Sources (ICANS-20) (USB Flash Drive), 6 Pages, 2012/03

This report investigates behaviors and damages of each component in a neutron target station of the MLF at the J-PARC at the time of the Great East Japan Earthquake (GEJE). At the date of the GEJE, in the MLF, strong quakes were detected at several instruments, an external power supply were lost, all of the circulation systems were shut down automatically, and a hydrogen gas was released as planned. Leakage of activation liquids and gases did not occur. While, the quakes made gaps between shield blocks and ruptured external pipe lines for air and water by subsidence. But significant damages on the components of the target station were not found though a loss of compressed air supply affected lock systems with air cylinders and pneumatic operation values. These results substantiated a validity of safety design on the target station for emergency accidents.

Journal Articles

Shielding experiments under JASMIN collaboration at Fermilab, 4; Measurement and analyses of high-energy neutron spectra in the anti-proton target station

Matsuda, Norihiro; Kasugai, Yoshimi; Sakamoto, Yukio; Nakashima, Hiroshi; Matsumura, Hiroshi*; Iwase, Hiroshi*; Kinoshita, Norikazu*; Hirayama, Hideo*; Yashima, Hiroshi*; Mokhov, N.*; et al.

Journal of the Korean Physical Society, 59(2), p.2055 - 2058, 2011/08

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

It is important to obtain neutron spectra and its intensity on shielding experiment. Deduction of high-energy neutron spectra were done using fitting and unfolding methods based on the shielding data obtained at the anti-proton (pbar) target station in Fermilab. The neutron spectra for fitting method is useful to be easily obtained and the values gave reasonable results compared with nuclear data. Therefore, that for unfolding methods included inconsistency. Furthermore, the deduced neutron spectra were verified through the calculation analyses by PHITS code.

Journal Articles

Shielding experiments by the JASMIN collaboration at Fermilab, 2; Radioactivity measurement induced by secondary particles from the anti-proton production target

Yashima, Hiroshi*; Matsuda, Norihiro; Kasugai, Yoshimi; Nakashima, Hiroshi; Sakamoto, Yukio; Matsumura, Hiroshi*; Iwase, Hiroshi*; Kinoshita, Norikazu*; Boehnlein, D.*; Lautenschlager, G.*; et al.

Journal of the Korean Physical Society, 59(2), p.2051 - 2054, 2011/08

 Times Cited Count:1 Percentile:11.37(Physics, Multidisciplinary)

The experiment was performed at the anti-proton (pbar) production target station in Fermi National Accelerator Laboratory. At the pbar target station, an anti-proton production target, consisted of Inconel and copper disks, were irradiated by 120 GeV proton beam. The beam intensity was 2.0 $$times$$ 10$$^{12}$$ proton per second. Al, Nb, Cu, Au samples were set around the target to investigate the spatial and energy distribution of secondary particles emitted from the target. After irradiation, induced activities of samples were measured by using HPGe detector. The reaction rates of 30 nuclides induced in Al, Nb, Cu, Au samples were obtained. The reaction rates of these nuclides increase for samples placed on forward angle position. The angle dependence of these reaction rates becomes larger for increasing threshold energy. These experimental results compared with the calculation. The calculated results generally agree with the experimental results within a factor of 3.

Journal Articles

Shielding experiments under JASMIN collaboration at Fermilab, 3; Measurement of high-energy neutrons penetrating a thick iron shield from the antiproton production target by Au activation method

Matsumura, Hiroshi*; Kinoshita, Norikazu*; Iwase, Hiroshi*; Toyoda, Akihiro*; Kasugai, Yoshimi; Matsuda, Norihiro; Sakamoto, Yukio; Nakashima, Hiroshi; Yashima, Hiroshi*; Mokhov, N.*; et al.

Journal of the Korean Physical Society, 59(2), p.2059 - 2062, 2011/08

 Times Cited Count:1 Percentile:11.37(Physics, Multidisciplinary)

In an antiproton production (Pbar) target station of the Fermi National Accelerator Laboratory (FNAL), the secondary particles produced by bombarding a target with 120-GeV protons are shielded by a thick iron shield. In order to obtain experimental data on high-energy proton accelerator facilities, we indirectly measured $$>$$ 100-MeV neutrons at the outside of the iron shield. The measurement was performed by using the Au activation method coupled with a low-background $$gamma$$-ray counting system. As an indicator for the neutron flux, we determined the production rates of 8 spallation nuclides ($$^{196}$$Au, $$^{188}$$Pt, $$^{189}$$Ir, $$^{185}$$Os, $$^{175}$$Hf, $$^{173}$$Lu, $$^{171}$$Lu, and $$^{169}$$Yb) in the Au activation detector. The measured production rates were compared with the theoretical production rates calculated using PHITS. We proved that the Au activation method can serve as a powerful tool for indirect measurements of $$>$$ 100-MeV neutrons that play a vital role in neutron transport.

Journal Articles

Shielding Design of a Neutron Beam Line "NOBORU" at JSNS/J-PARC

Harada, Masahide; Oikawa, Kenichi; Kasugai, Yoshimi; Maekawa, Fujio

Progress in Nuclear Science and Technology (Internet), 1, p.94 - 97, 2011/02

NOBORU is one of 23 neutron beam ports in JSNS/J-PARC to measure neutron source characteristics and to be applicable to various test experiments. Shielding for NOBORU must be tough due to the large neutron beam size and the high beam power at 1MW. In this study, we determined the shielding structure of NOBORU by neutronics calculations. In the shielding calculation, we considered neutron beam loss conditions caused by various beam line components. As a result, shielding structures that satisfied all the necessary radiation dose limits adopted in the J-PARC were determined. We measured dose rates in the experimental room of NOBORU during operation. The measured values were in good agreement with the calculated ones within a factor of 2. In addition, we also evaluated the effectiveness of a neutron beam shutter and radioactivity of the T$$_{0}$$ chopper.

Journal Articles

Shielding experiments at high energy accelerators of Fermilab, 2; Spatial distribution measurement of reaction rate behind the shield and its application for Moyer model

Yashima, Hiroshi*; Kasugai, Yoshimi; Matsuda, Norihiro; Matsumura, Hiroshi*; Iwase, Hiroshi*; Kinoshita, Norikazu*; Mokhov, N.*; Leveling, A.*; Boehnlein, D.*; Vaziri, K.*; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.48 - 51, 2011/02

The shielding experiment was performed at the anti-proton production target station in Fermi National Accelerator Laboratory. Aluminum, Bismath, Niobium, Copper and Indium samples were placed behind the shields. After irradiation, induced activities of samples were measured by using HPGe detector. The spatial distribution of reaction rate of samples which were placed behind the iron and concrete shields were obtained. The measured data shows that the reaction rates on the outer surfaces of the iron and concrete shields increases toward the downstream of the target. The obtained reaction rates were also fitted to Moyer's formula, and the attenuation lengths for iron and concrete shields were obtained.

Journal Articles

Shielding experiments at high energy accelerators of Fermilab, 4; Calculation analyses

Matsuda, Norihiro; Kasugai, Yoshimi; Matsumura, Hiroshi*; Yashima, Hiroshi*; Iwase, Hiroshi*; Kinoshita, Norikazu*; Sanami, Toshiya*; Mokhov, N.*; Leveling, A.*; Boehnlein, D.*; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.57 - 60, 2011/02

The anti-proton (pbar) production target in Fermi National Accelerator Laboratory can be produced a wide variety of secondary particles including of anti-protons, by bombarding with protons accelerated to 120 GeV. The shielding experimental data, which was obtained around the pbar target, make possible to validate the accuracies of the general-purpose Monte Carlo simulation codes. In this paper, spatial distribution of reaction rates were calculated with two-dimensional (r-z) geometry simplified the real pbar target station using the PHITS, MARS and MCNPX code. These experimental data in iron shield were compared with the calculated data. The comparison for attenuation length of iron were good agreement between the experiments and calculations.

Journal Articles

Distinctive features in neutronic performance of JSNS

Maekawa, Fujio; Oikawa, Kenichi; Harada, Masahide; Teshigawara, Makoto; Kai, Tetsuya; Kasugai, Yoshimi; Meigo, Shinichiro; Oi, Motoki; Futakawa, Masatoshi; Watanabe, Noboru*; et al.

Proceedings of 19th Meeting of the International Collaboration on Advanced Neutron Sources (ICANS-19) (CD-ROM), 8 Pages, 2010/07

Efforts have been made to characterize neutronic performance of JSNS. A NOBORU instrument was mainly used for this purpose while some other instruments were used when needed. The followings were confirmed. (1) Judging from a measured spectral shape, a para-hydrogen fraction in the hydrogen moderator was very close to unity as expected due to introduction of catalyst in a hydrogen circulation system. (2) Measured data for absolute spectral intensity and pulse shapes agreed very well with simulation calculations, and suggested adequacy of the neutron source designs. (3) The world's highest resolution of 0.035 % was recorded at the powder diffractometer SuperHRPD. (4) A total neutron flux of 3 $$times$$ 10$$^{9}$$n/s/cm$$^{2}$$ was confirmed at the chopper instrument 4SEASONS when it was normalized to 1 MW. The flux is the world's highest among existing spallation neutron sources, and is comparable to fluxes at intense reactor sources even in time-averaged value.

117 (Records 1-20 displayed on this page)