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Journal Articles

Chemical species of iodine during sorption by activated carbon; Effects of original chemical species and fulvic acids

Kato, Tomoaki; Kozai, Naofumi; Tanaka, Kazuya; Kaplan, D. I.*; Utsunomiya, Satoshi*; Onuki, Toshihiko

Journal of Nuclear Science and Technology, 59(5), p.580 - 589, 2022/05

 Times Cited Count:1 Percentile:0.01(Nuclear Science & Technology)

This study reports the effect of fulvic acids, which is a natural organic substance generally contained in groundwater, on the oxidation states of radioactive iodine anions (iodide and iodate). Iodide and iodate are contained in the contaminated water of the Fukushima Daiichi Nuclear Power Plant and supposed to be removed by activated carbon (AC) via adsorption. When fulvic acids does not exist in the experimental system, the adsorption of iodide on AC was less than that of iodate and their oxidation states after the adsorption were not changed. When fulvic acids existed, a fraction of the adsorbed iodate was reduced to iodide. This result indicates that the reduction of the adsorbed iodate progresses during the storage of the spent AC.

Journal Articles

Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation

Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.

Journal of Nuclear Science and Technology, 32 Pages, 2022/02

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.

Journal Articles

Reduction behaviors of permanganate by microbial cells and concomitant accumulation of divalent cations of Mg$$^{2+}$$, Zn$$^{2}$$+, and Co$$^{2+}$$

Kato, Tomoaki*; Yu, Q.*; Tanaka, Kazuya; Kozai, Naofumi; Saito, Takumi*; Onuki, Toshihiko

Journal of Environmental Sciences, 86, p.78 - 86, 2019/12

 Times Cited Count:0 Percentile:0(Environmental Sciences)

This paper investigated the fate of the dissolved permanganate in aqueous solution after contact with bacterial cells and metal accumulation during precipitation of Mn oxides. When Mn(VII) was contacted with bacterial cells, cells were damaged and Mn(VII) was reduced by cells to lower valence and precipitated as Mn oxides (biomass Mn oxides). When Co$$^{2+}$$ ions were present, Co was incorporated into Mn oxides as Co$$^{3+}$$. These results suggest that Mn(VII) can be used to remove metal ions when introduced to wastewater as disinfectant.

Journal Articles

Upgrade of the 3-MeV linac for testing of accelerator components at J-PARC

Kondo, Yasuhiro; Hirano, Koichiro; Ito, Takashi; Kikuzawa, Nobuhiro; Kitamura, Ryo; Morishita, Takatoshi; Oguri, Hidetomo; Okoshi, Kiyonori; Shinozaki, Shinichi; Shinto, Katsuhiro; et al.

Journal of Physics; Conference Series, 1350, p.012077_1 - 012077_7, 2019/12

 Times Cited Count:0 Percentile:0.07

We have upgraded a 3-MeV linac at J-PARC. The ion source is same as the J-PARC linac's, and the old 30-mA RFQ is replaced by a spare 50-mA RFQ, therefore, the beam energy is 3 MeV and the nominal beam current is 50 mA. The main purpose of this system is to test the spare RFQ, but also used for testing of various components required in order to keep the stable operation of the J-PARC accelerator. The accelerator has been already commissioned, and measurement programs have been started. In this paper, present status of this 3-MeV linac is presented.

Journal Articles

Decommissioning plan of JRR-4

Ishikuro, Yasuhiro; Hirane, Nobuhiko; Kato, Tomoaki

Proceedings of European Research Reactor Conference 2018 (RRFM 2018) (Internet), 7 Pages, 2018/03

Japan Research Reactor No.4 (JRR-4) is a swimming pool type reactor moderated and cooled with light-water. The maximum thermal power of JRR-4 is 3,500kW. Since its initial criticality in January 1965, JRR-4 had been operated about 45 years until in December 2010.Subsequently, the Great East Japan Earthquake occurred on March 11, 2011. Although JRR-4 was no severe damage, we have determined to decommission JRR-4 in consideration of various things. After that, we have submitted the decommissioning plan of JRR-4 to the nuclear regulatory body and have received the approval of it on June 7, 2017. Consequently, JRR-4 has shifted to the phase1 of the decommissioning plan since December.15, 2017 after the approval of its the safety regulation.

Journal Articles

A Failure investigation of the beam collimator system in the J-PARC 3 GeV rapid cycling synchrotron

Okabe, Kota; Yamamoto, Kazami; Kamiya, Junichiro; Takayanagi, Tomohiro; Yamamoto, Masanobu; Yoshimoto, Masahiro; Takeda, Osamu*; Horino, Koki*; Ueno, Tomoaki*; Yanagibashi, Toru*; et al.

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.853 - 857, 2017/12

The most important issue is to reduce the uncontrolled beam loss in the high intensity hadron accelerator such as J-PARC proton accelerators. The J-PARC 3 GeV Synchrotron (RCS) has a collimator system which narrows a high intensity beam in the RCS. After startup of RCS in 2007, the collimator system of the RCS worked well. However, in April 2016, vacuum leakage at the collimator system occurred during the maintenance operation. To investigate a cause of the failure, we took apart iron shields of the collimator reducing exposed dose of operators. As a result of inspection, we succeeded to identify the cause of the vacuum leakage failure. In this presentation, we report the failure investigation of the beam collimator system in the RCS.

Journal Articles

Beam-loss monitoring signals of interlocked events at the J-PARC Linac

Hayashi, Naoki; Kato, Yuko; Miura, Akihiko; Futatsukawa, Kenta*; Miyao, Tomoaki*

Proceedings of 5th International Beam Instrumentation Conference (IBIC 2016) (Internet), p.368 - 371, 2017/03

It is important to understand why the beam loss occurs during user operation. It is understandable that the beam loss results from RF cavities failure. However, it would be still useful to study the beam loss detailed mechanism and to know which beam loss monitor (BLM) experiences the highest loss or is most sensitive. This may lead a reduction in the number of interlocked events and a more stable accelerator operation. The J-PARC Linac BLM has a simple data recorder that comprises multiple oscilloscopes. Although its functionality is limited, it can record events when an interlock is triggered. Of particular interest here are the events associated with only the BLM Machine Protection System (MPS). These may reveal hidden problems with the accelerator.

Journal Articles

Precise current adjustment of the power supply for the injection painting magnets in the J-PARC RCS

Kato, Shinichi; Takayanagi, Tomohiro; Harada, Hiroyuki; Horino, Koki; Tobita, Norimitsu; Ueno, Tomoaki*; Kinsho, Michikazu

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1180 - 1184, 2015/09

For the high intensity proton accelerator, the mitigation of the space charge force is most important because it causes the beam loss. For mitigation, the painting injection method which arranges the injection beam on the wide phase-space area during the multi-turn injection has been performed to expand the circulating beam in the J-PARC RCS. In the horizontal plane, the position and angle of the injection beam are fixed and these of the circulating beam are changed during the painting injection. Specifically, the time variation of the bump orbit height at the injection point is generated by the 4 paint bump magnet whose power supply are separate. Hence, the accuracy of the painting injection depend on the power conditioning precision of the magnet power supply. Therefore, the output characteristics of the power supply was examined for the precise power conditioning. In addition, the automatic conditioning tool has been developed based on that results.

Journal Articles

Present status of J-PARC linac

Oguri, Hidetomo; Hasegawa, Kazuo; Ito, Takashi; Chishiro, Etsuji; Hirano, Koichiro; Morishita, Takatoshi; Shinozaki, Shinichi; Ao, Hiroyuki; Okoshi, Kiyonori; Kondo, Yasuhiro; et al.

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.389 - 393, 2014/10

no abstracts in English

Journal Articles

Interlock system of beam line for beam current upgrade

Kawane, Yusuke*; Miura, Akihiko; Miyao, Tomoaki*; Hirano, Koichiro; Sugimura, Takashi*; Kato, Yuko; Sawabe, Yuki; Fukuda, Shimpei; Ouchi, Nobuo

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1288 - 1291, 2014/10

In the J-PARC Linac, because an upgrading of a beam current up to 50mA using an RF-driven ion source and a new RFQ Linac cavity is in progress, we have developed a new frontend equipments. In order to protect the scraper against 50 mA, we need to observe the temperature and to avoid the excess heat loading of the scraper surface and to count the irradiated beam particles. We also monitor the beam transmission between the upstream and downstream of the chopper cavity to check the chopping errors using the beam current monitors. We fabricated the interlock system for the temperature, irradiated particle numbers and beam transmission. And we tested them in the test stand with actual beam. This paper describes the interlock system and their test results.

Journal Articles

Observation of deep levels and their hole capture behavior in p-type 4H-SiC epilayers with and without electron irradiation

Kato, Masashi*; Yoshihara, Kazuki*; Ichimura, Masaya*; Hatayama, Tomoaki*; Oshima, Takeshi

Japanese Journal of Applied Physics, 53(4S), p.04EP09_1 - 04EP09_5, 2014/04

 Times Cited Count:5 Percentile:25.13(Physics, Applied)

Journal Articles

Impact of carrier lifetime on efficiency of photolytic hydrogen generation by p-type SiC

Miyake, Keiko*; Yasuda, Tomonari*; Kato, Masashi*; Ichimura, Masaya*; Hatayama, Tomoaki*; Oshima, Takeshi

Materials Science Forum, 778-780, p.503 - 506, 2014/02

Journal Articles

Excess carrier lifetime in p-type 4H-SiC epilayers with and without low-energy electron irradiation

Kato, Masashi*; Matsushita, Yoshinori*; Ichimura, Masaya*; Hatayama, Tomoaki*; Oshima, Takeshi

Japanese Journal of Applied Physics, 51(2), p.028006_1 - 028006_2, 2012/02

 Times Cited Count:14 Percentile:54.09(Physics, Applied)

Excess carrier lifetimes in as-grown and low-energy electron irradiated p-type 4H-SiC epitaxial layers were investigated using the microwave photoconductivity decay method. The carrier lifetime increased with increasing excitation density in the epilayers. This results suggests that the dominant recombination center in the epilayers has larger capture cross section for electrons than capture cross section for holes. The carrier lifetime in the epilayer decreased by the low-energy electron irradiation decreases. The decrease in lifetime in the electron irradiated samples showed recovery after annealing at 1000 $$^{circ}$$C.

Journal Articles

Magnetic structure determination of Ce$$T_{2}$$Al$$_{10}$$ ($$T$$ = Ru and Os); Single crystal neutron diffraction studies

Kato, Harukazu*; Kobayashi, Riki; Takesaka, Tomoaki*; Nishioka, Takashi*; Matsumura, Masahiro*; Kaneko, Koji; Metoki, Naoto

Journal of the Physical Society of Japan, 80(7), p.073701_1 - 073701_4, 2011/07

 Times Cited Count:58 Percentile:89.83(Physics, Multidisciplinary)

JAEA Reports

Criticality analyses of the JRF-90Y-950K package for research reactors; Under consideration of deformation for oblique drops onto a bar

Araki, Masaaki; Kato, Tomoaki; Arai, Masaji

JAEA-Technology 2010-015, 35 Pages, 2010/06


Research reactor JRR-3 is a light water moderated and cooled pool type research reactor using low enriched uranium-silicon-aluminum-dispersion-type fuel. French Competent Authority (FCA) required that the criticality safety of the JRF-90Y-950K package is maintained even if it is deformed under oblique drops onto a bar. Criticality analyses of the JRF-90Y-950K package were carried out for the transport of JRR-3, JRR-4 or JMTR fuel. The results show that criticality safety is kept even if it is deformed under oblique drops onto a bar.

Journal Articles

Characterization of the excess carrier lifetime of as-grown and electron irradiated epitaxial p-type 4H-SiC layers by the microwave photoconductivity decay method

Matsushita, Yoshinori*; Kato, Masashi*; Ichimura, Masaya*; Hatayama, Tomoaki*; Oshima, Takeshi

Materials Science Forum, 645-648, p.207 - 210, 2010/00

Silicon carbide (SiC) is a promising material for radiation hardness devices. In this study, we evaluated excess carrier decay curves in both as-grown and electron-irradiated p-type 4H-SiC layers by the microwave photoconductivity decay ($$mu$$-PCD) method. The samples used in this study were an Al-doped p-type epitaxial layer grown on a Si-face B doped bulk p-type 4H-SiC. The samples were irradiated with electrons at an energy of 160 keV and at a doses of 1$$times$$10$$^{16}$$ cm$$^{-2}$$ (ele-16) and 1$$times$$10$$^{17}$$ cm$$^{-2}$$ (ele-17). As a results of $$mu$$-PCD measurements, the lifetimes of free carriers for as-grown, ele-16 and ele-17 were estimated to be 0.14 $$mu$$s, 0.07 $$mu$$s and 0.04 $$mu$$s, respectively. This result indicates that defects acting as recombination centers were introduced by the electron irradiation.

JAEA Reports

Reactivity management and burn-up management on JRR-3 silicide-fuel-core

Kato, Tomoaki; Araki, Masaaki; Izumo, Hironobu; Kinase, Masami; Torii, Yoshiya; Murayama, Yoji

JAEA-Technology 2007-050, 39 Pages, 2007/08


On the conversion from aluminide fuel to silicide fuel, burnable absorbers were introduced for decreasing excess reactivity. The burnable absorbers influence reactivity during reactor operation. So, the burning of the burnable absorbers was studied and the influence on reactor operation was made cleared. Furthermore, necessary excess reactivity on beginning of operation cycle and the time limit for restart after unplanned reactor shutdown was calculated. After the conversion, the fuel exchange procedure was changed from the six-batch dispersion procedure to the fuel burn-up management procedure. The previous estimation of fuel burn-up was required for the planning of fuel exchange, so that the estimation was carried out by means of past operation data. Finally, a new fuel exchange procedure was proposed for effective use of fuel elements. The average length of fuel-staying in the core can be increased by two percent on the procedure.

JAEA Reports

JRR-3 maintenance program utilizing accumulated maintenance data

Izumo, Hironobu; Kato, Tomoaki; Kinase, Masami; Torii, Yoshiya; Murayama, Yoji

JAEA-Technology 2007-046, 23 Pages, 2007/07


JRR-3 (Japan Research Reactor No.3) has been operated for about 15 years after the modification, without significant troubles by carrying out maintenance such as the preventive maintenance (mainly Time-Based Maintenance: TBM) for the safety-grade equipments and the breakdown maintenance for the non-safety-grade equipments. Recently, numbers of unscheduled shutdowns caused by aging of the non-safety-grade equipment have been increasing, but resources for both maintenances have been decreasing year by year. In such a situation, new JRR-3 maintenance program is studying and reviewed considering safety, reliability and economical. In the evaluation, the maintenance data (i.e. vibration, measurement, etc.) which accumulated on JRR-3 is applied effectively. This report offers the policy on the maintenance review at JRR-3 and the future direction of JRR-3 maintenance programs.

Journal Articles

Mechanisms and kinetics of the post-spinel transformation in Mg$$_{2}$$SiO$$_{4}$$

Kubo, Tomoaki*; Otani, Eiji*; Kato, Takumi*; Urakawa, Satoru*; Suzuki, Akio*; Kambe, Yuichi*; Funakoshi, Kenichi*; Utsumi, Wataru; Kikegawa, Takumi*; Fujino, Kiyoshi*

Physics of the Earth and Planetary Interiors, 129(1-2), p.153 - 171, 2002/01

 Times Cited Count:48 Percentile:66.36(Geochemistry & Geophysics)

no abstracts in English

Journal Articles

The Effect of temperature, pressure, and sulfur content on viscosity of the Fe-FeS melt

Terasaki, Hidenori*; Kato, Takumi*; Urakawa, Satoru*; Funakoshi, Kenichi*; Suzuki, Akio*; Okada, Taku; Maeda, Makoto*; Sato, Jin*; Kubo, Tomoaki*; Kasai, Shizu*

Earth and Planetary Science Letters, 190(1-2), p.93 - 101, 2001/07

 Times Cited Count:49 Percentile:68.73(Geochemistry & Geophysics)

The Fe-FeS melt is thought to be the major candidate of the outer core material. Its viscosity is one of the most important physical properties to study the dynamics of the convection in the outer core. We performed the in situ viscosity measurement of the Fe-FeS melt under high pressure using X-ray radiography falling sphere method with a novel sample assembly. Viscosity was measures in the temperature, pressure, and compositional conditions of 1233-1923 K, 1.5-6.9 GPa, and Fe-Fe $$_{72}$$ S $$_{28}$$ (wt %), respectively. The viscosity coefficients obtained by 17 measurements change systematically in the range of 0.008-0.036 Pa s. An activation energy of the viscous flow, 30 kJ/mol, and the activation volume, 1.5 cm $$^{3}$$ /mol, are determined as the temperature and pressure dependence, and the viscosity of the Fe $$_{72}$$ S $$_{28}$$ melt is found to be smaller than that of the Fe melt by 15 %. These tendencies can be well correlated with the structural variation of the Fe-FeS melt.

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