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Journal Articles

Visualizing cation vacancies in Ce:Gd$$_{3}$$Al$$_{2}$$Ga$$_{3}$$O$$_{12}$$ scintillators by gamma-ray-induced positron annihilation lifetime spectroscopy

Fujimori, Kosuke*; Kitaura, Mamoru*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Watanabe, Shinta*; Kamada, Kei*; Okano, Yasuaki*; Kato, Masahiro*; Hosaka, Masahito*; et al.

Applied Physics Express, 13(8), p.085505_1 - 085505_4, 2020/08

 Times Cited Count:0 Percentile:100(Physics, Applied)

To clarify the existence of cation vacancies in Ce-doped Gd$$_{3}$$Al$$_{2}$$Ga$$_{3}$$O$$_{12}$$ (Ce:GAGG) scintillators, we performed gamma-ray-induced positron annihilation lifetime spectroscopy (GiPALS). GiPAL spectra of GAGG and Ce:GAGG comprised two exponential decay components, which were assigned to positron annihilation at bulk and defect states. By an analogy with Ce:Y$$_{3}$$Al$$_{5}$$O$$_{12}$$, the defect-related component was attributed to Al/Ga-O divacancy complexes. This component was weaker for Ce, Mg:GAGG, which correlated with the suppression of shallow electron traps responsible for phosphorescence. Oxygen vacancies were charge compensators for Al/Ga vacancies. The lifetime of the defect-related component was significantly changed by Mg co-doping. This was understood by considering aggregates of Mg$$^{2+}$$ ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.

Journal Articles

Preventing nuclear fuel material adhesion on glove box components using nanoparticle coating

Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Tachihara, Joji; Takato, Kiyoto; Okita, Takatoshi; Satone, Hiroshi*; Suzuki, Michitaka*

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08

To reduce the hold-up of the nuclear fuel materials in the glove box and the external exposure dose, the technology of the MOX powder adhesion prevention by the nanoparticle coating to the acrylic panels of the glove box has been developed. Due to the formation of nano-sized tiny rugged surface, the nanoparticle coating reduced the minimum adhesion force between the UO$$_{2}$$ particles and the acrylic test piece surface with the smallest particle size of about 5 $$mu$$m where desorption was observed, by about one-tenth. Moreover, the nanoparticle coating reduced the amount of the MOX powder adhering to the acrylic test piece to about one-tenth. In this study, it was found that applying the nanoparticle coating to the acrylic panels of glove box can prevent the adhesion of nuclear fuel materials. This method is effective for reducing the hold-up of the nuclear fuel materials in the glove box, the external exposure dose and improving the visibility of the acrylic panels.

Journal Articles

Study on optimizing microwave heating denitration method and powder characteristics of uranium trioxide

Segawa, Tomoomi; Kawaguchi, Koichi; Kato, Yoshiyuki; Ishii, Katsunori; Suzuki, Masahiro; Fujita, Shunya*; Kobayashi, Shohei*; Abe, Yutaka*; Kaneko, Akiko*; Yuasa, Tomohisa*

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 9 Pages, 2019/05

A solution of plutonium nitrate and uranyl nitrate is converted into a mixed oxide by microwave heating denitration method. In the present study, for improving the efficiency of microwave heating and achieving high-temperature uniformity to produce homogeneous UO$$_{3}$$ powder, the microwave heating test of potassium chloride and uranyl nitrate solution, and numerical simulation analysis were conducted. The potassium chloride agar was adjusted to the dielectric loss, which is close to that of the uranyl nitrate solution and the optimum support table height was estimated to be 50 mm for denitration of the uranyl nitrate solution by microwave heating. The adiabator improved the efficiency of microwave heating denitration. Moreover, the powder yield was improved by using the adiabator owing to ease of scraping of the denitration product from the bottom of the denitration vessel.

Journal Articles

Investigation of removal factors of various materials inside houses after Nuclear Power Station Accident

Mori, Airi; Ishizaki, Azusa; Futemma, Akira; Tanabe, Tsutomu; Wada, Takao; Kato, Mitsugu; Munakata, Masahiro

Hoken Butsuri (Internet), 54(1), p.45 - 54, 2019/04

Journal Articles

Effect of re-oxidation rate of additive cations on corrosion rate of stainless steel in boiling nitric acid solution

Irisawa, Eriko; Yamamoto, Masahiro; Kato, Chiaki; Motooka, Takafumi; Ban, Yasutoshi

Journal of Nuclear Science and Technology, 56(4), p.337 - 344, 2019/04

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

Recent progress of J-PARC RCS beam commissioning; Efforts for realizing a high-intensity low-emittance beam

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.95 - 99, 2017/12

no abstracts in English

Journal Articles

Status of proof-of-principle experiment for 400 MeV H$$^{-}$$ stripping to protons by using only lasers in the 3-GeV RCS of J-PARC

Saha, P. K.; Harada, Hiroyuki; Yamane, Isao*; Kinsho, Michikazu; Miura, Akihiko; Okabe, Kota; Liu, Y.*; Yoshimoto, Masahiro; Kato, Shinichi; Irie, Yoshiro*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.866 - 870, 2017/12

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

Effect of oxidizing metallic ions on corrosion of stainless steel during concentration process simulating High-level Activity Liquid Waste (HALW) concentrator

Irisawa, Eriko; Kato, Chiaki; Kamoshida, Michio*; Hakamatsuka, Yasuyuki*; Ueno, Fumiyoshi; Yamamoto, Masahiro

Proceedings of European Corrosion Congress 2017 (EUROCORR 2017) and 20th ICC & Process Safety Congress 2017 (USB Flash Drive), 9 Pages, 2017/09

Journal Articles

Achievement of a low-loss 1-MW beam operation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; et al.

Physical Review Accelerators and Beams (Internet), 20(6), p.060402_1 - 060402_25, 2017/06

 Times Cited Count:14 Percentile:11.18(Physics, Nuclear)

The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) is the world's highest class of high-power pulsed proton driver, aiming for an output beam power of 1 MW. The most important issues in realizing such a high-power beam operation are to control and minimize beam loss for maintaining machine activations within permissible levels. In RCS, numerical simulation was successfully utilized along with experimental approaches to isolate the mechanism of beam loss and find its solution. By iteratively performing actual beam experiments and numerical simulations, and also by several hardware improvements, we have recently established a 1-MW beam operation with very low fractional beam loss of a couple of 10$$^{-3}$$. In this paper, our recent efforts toward realizing such a low-loss high-intensity beam acceleration are presented.

Journal Articles

Realizing a high-intensity low-emittance beam in the J-PARC 3-GeV RCS

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro

Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2470 - 2473, 2017/06

For this past year, RCS beam tuning was focused on realizing a high-intensity low-emittance beam required from the downstream facility. The extraction beam emittance including its tail part was successfully decreased by optimizing transverse injection painting, and tune and chromaticity manipulations, where bipolar sextupole field patterns were newly introduced to simultaneously achieve emittance growth mitigation at the early stage of acceleration and beam instability suppression after the middle stage of acceleration. This paper presents the recent experimental results, together with detailed discussions for the emittance growth and its mitigation mechanisms.

JAEA Reports

Case studies of radiation dose assessment in emergency situation of nuclear facilities

Kawasaki, Masatsugu; Nakajima, Junya; Yoshida, Keisuke; Kato, Saori; Nishino, Sho; Nozaki, Teo; Nakagawa, Masahiro; Tsunoda, Junichi; Sugaya, Yuki; Hasegawa, Rie; et al.

JAEA-Data/Code 2017-004, 57 Pages, 2017/03

JAEA-Data-Code-2017-004.pdf:2.34MB

In emergency situation of nuclear facilities, we need to estimate the radiation dose due to radiation and radioactivity to grasp the influence range of the accident in the early stage. Therefore, we prepare the case studies of dose assessment for public exposure dose and personal exposure dose and contribute them to emergency procedures. This document covers about accidents of nuclear facilities in Nuclear Science Research Institute and past accident of nuclear power plant, and it can be used for inheritance of techniques of emergency dose assessment.

Journal Articles

1 MW beam tuning for beam loss mitigation in the J-PARC 3 GeV RCS

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.61 - 65, 2016/11

After the RF power supply upgrade, the J-PARC 3-GeV RCS restarted a 1-MW beam test in October 2015. In the beam test in October, we successfully removed longitudinal beam loss by beam loading compensation as well as minimized space-charge induced beam loss by injection painting. In addition, in this beam test, beam instability was also well suppressed by controlling the tune and the chromaticity. Furthermore, in the following beam test, the transverse painting area was successfully expanded by introducing both quadrupole correctors and anti-correlated painting scheme, by which a foil scattering part of beam loss during charge-exchange injection was further reduced. By these recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents recent progresses of 1-MW beam tuning with particular emphasis on our approaches to beam loss issues.

Journal Articles

The Effect of crystal textures on the anodic oxidization of zirconium in a boiling nitric acid solution

Kato, Chiaki; Ishijima, Yasuhiro; Ueno, Fumiyoshi; Yamamoto, Masahiro

Journal of Nuclear Science and Technology, 53(9), p.1371 - 1379, 2016/09

AA2015-0626.pdf:1.2MB

 Times Cited Count:2 Percentile:69.03(Nuclear Science & Technology)

The effects of crystal textures and the potentials in the anodic oxidation of zirconium in a boiling nitric acid solution were investigated to study the stress corrosion cracking of zirconium in nitric acid solutions. The growth of the zirconium oxide film dramatically changed depending on the applied potential at a closed depassivation potential (1.47 V vs. SSE). At 1.5 V, the zirconium oxide film rapidly grows, and its growth exhibits cyclic oxidation kinetics in accordance with a nearly cubic rate law. The zirconium oxide film grows according to the quantity of electric charge, and the growth rate does not depend on the crystal texture in the pretransition region before the cyclic oxidation kinetics. However, the growth and cracking under the thick oxide film depend on the crystal texture in the transition region. On the normal direction side, the oxide film thickness decreases on average since some areas of the thick oxide film are separated from the specimen surface owing to the cracks in the thick oxide. On the rolling direction side, cracks are found under the thick oxide film, which deeply propagate along the RD without an external stress. The cracks under the thick oxide film propagate to the center of the oxide layer. The cracks in the oxide layer propagate in the (0002)Zr plane in the zirconium matrix. The oxide layer consists of string-like zirconium oxide and zirconium hydride. The string-like zirconium oxide contains orthorhombic ZrO$$_{2}$$ in addition to monoclinic ZrO$$_{2}$$. As one assumption for the mechanism of crack initiation and propagation without an external stress, it is considered that the oxidizing zirconium hydrides precipitate in the (0002)Zr and then the phase transformation from orthorhombic ZrO$$_{2}$$ to monoclinic ZrO$$_{2}$$ in the oxide layer causes the crack propagation in the (0002) plane.

Journal Articles

Effect of boiling of nitric acid solution on corrosion of Stainless steel-made concentrator in reduced pressure

Ueno, Fumiyoshi; Irisawa, Eriko; Kato, Chiaki; Igarashi, Takahiro; Yamamoto, Masahiro; Abe, Hitoshi

Proceedings of European Corrosion Congress 2016 (EUROCORR 2016) (USB Flash Drive), 7 Pages, 2016/09

In this study, we focused on the effect of the boiling of nitric acid solution on the corrosion of a stainless steel-made concentrator in reduced pressure in fuel reprocessing plant. In order to perform the simulation test in a non-radioactive condition, nitric acid solution with the addition of vanadium as an oxidizing metal ion were used. Corrosion tests were carried out under the conditions of boiling at reduced pressure, and of non-boiling at normal pressure and several temperatures. As a result, corrosion was accelerated by the solution boiling while it was not by non-boiling at the same temperature. It was found also that the temperature dependence of corrosion rate is the same in the both conditions of boiling and non-boiling. The corrosion accelerating effect will be discussed on the basis of the reaction among nitric acid, NOx and vanadium, etc.

Journal Articles

Recent progress of 1-MW beam tuning in the J-PARC 3-GeV RCS

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.

Proceedings of 7th International Particle Accelerator Conference (IPAC '16) (Internet), p.592 - 594, 2016/06

The J-PARC 3-GeV RCS achieved a 1-MW beam acceleration in January 2015. Since then, a large fraction of our effort has been focused on reducing and managing beam losses. Major part of beam loss, such as space-charge induced beam loss, was well minimized by introducing injection painting. Uncontrolled beam loss arising from large-angle foil scattering during charge-exchange injection was also reduced drastically by the expansion of the transverse painting area, which was achieved by introducing quadrupole correctors and anti-correlated painting. By such recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents the recent progress of 1-MW beam tuning, especially focusing on our approaches to beam loss issues.

Journal Articles

Beam loss caused by edge focusing of injection bump magnets and its mitigation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki; Tani, Norio; Watanabe, Yasuhiro; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Tamura, Fumihiko; Yoshimoto, Masahiro

Physical Review Accelerators and Beams (Internet), 19(1), p.010401_1 - 010401_11, 2016/01

AA2015-0742.pdf:2.84MB

 Times Cited Count:7 Percentile:36.92(Physics, Nuclear)

In the J-PARC 3-GeV RCS, transverse injection painting is utilized not only to suppress space-charge induced beam loss but also to mitigate foil scattering beam loss during charge-exchange injection. The space-charge induced beam loss is well minimized by the combination of modest transverse painting and full longitudinal painting. But, for sufficiently mitigating the foil scattering beam loss, the transverse painting area has to be further expanded. However, such a wide-ranging transverse painting had not been realized until recently due to beta function beating caused by edge focusing of pulsed injection bump magnets. This beta function beating additionally excites random betatron resonances, causing significant extra beam loss when expanding the transverse painting area. To solve this issue, we newly installed pulse-type quadrupole correctors to compensate the beta function beating. This paper presents recent experimental results on this correction scheme, while discussing the beam loss and its mitigation mechanisms.

Journal Articles

Using LiF crystals for high-performance neutron imaging with micron-scale resolution

Faenov, A.*; Matsubayashi, Masahito; Pikuz, T.*; Fukuda, Yuji; Kando, Masaki; Yasuda, Ryo; Iikura, Hiroshi; Nojima, Takehiro; Sakai, Takuro; Shiozawa, Masahiro*; et al.

High Power Laser Science and Engineering, 3, p.e27_1 - e27_9, 2015/10

 Times Cited Count:7 Percentile:49.7(Optics)

Journal Articles

Localized corrosion behavior of stainless steel in the diluted artificial sea-water contacted with zeolite under $$gamma$$-ray irradiation

Kato, Chiaki; Sato, Tomonori; Nakano, Junichi; Ueno, Fumiyoshi; Yamagishi, Isao; Yamamoto, Masahiro

Nippon Genshiryoku Gakkai Wabun Rombunshi, 14(3), p.181 - 188, 2015/09

In relation to the consideration for long-term storage of spent Cs adsorption vessels containing zeolites in the Fukushima Daiichi Nuclear Power Station, corrosion of the vessel material in the spent Cs adsorption vessel is one of important issues. We performed electrochemical tests of stainless steel (SUS 316L) in the zeolites containing artificial seawater under $$gamma$$-ray irradiation. The spontaneous potential ($$E_{rm SP}$$) and critical pitting potential ($$V_{rm c}$$), of SUS 316L were measured to understand the corrosion resistance of the stainless steel in this study. The rest potential of the stainless steel increased with increasing time after $$gamma$$-ray irradiation. The $$E_{rm SP}$$, defined as the steady rest potential, increased with increasing dose rate, while increasing $$E_{rm SP}$$ was suppressed by contact with the zeolites. Concentration of H$$_{2}$$O$$_{2}$$ in bulk water increased with increasing dose rate. The concentration increasing was suppressed by contact with the zeolites due to decomposition of H$$_{2}$$O$$_{2}$$. There was good relationship between $$E_{rm SP}$$ and the concentration of H$$_{2}$$O$$_{2}$$. The $$V_{rm c}$$ of SUS 316L contacted with the zeolites decreased with increasing Cl$$^{-}$$ ion concentration and is slightly smaller than the $$V_{rm c}$$ in the bulk water. The contact with the zeolites causes the suppressant of increasing $$E_{rm SP}$$ under the irradiation. The contact with the zeolite can reduce probability in the localized corrosion for SUS 316L.

Journal Articles

Effect of zeolites on the corrosion potential of type 316L stainless steel in diluted artificial sea water under gamma-ray irradiation

Kato, Chiaki; Sato, Tomonori; Ueno, Fumiyoshi; Yamagishi, Isao; Yamamoto, Masahiro

Zairyo To Kankyo 2015 Koenshu (CD-ROM), p.83 - 86, 2015/05

In relation to the consideration for long-term storage of spent Cs adsorption vessels containing zeolites in the Fukushima Daiichi Nuclear Power Station, corrosion of the vessel material in the spent Cs adsorption vessel is one of important issues. We performed electrochemical tests of stainless steel (SUS 316L) in the zeolites containing artificial seawater under gamma-ray irradiation. The spontaneous potential (ESP) and critical pitting potential (VC), of SUS316L were measured to understand the corrosion resistance of the stainless steel in this study. The rest potential of the stainless steel increased with increasing time after gamma-ray irradiation. The ESP, defined as the steady rest potential, increased with increasing dose rate, while increasing ESP was suppressed by contact with the zeolites. Concentration of H$$_{2}$$O$$_{2}$$ in bulk water increased with increasing dose rate. The concentration increasing was suppressed by contact with the zeolites due to decomposition of H$$_{2}$$O$$_{2}$$. There was good relationship between ESP and the concentration of H$$_{2}$$O$$_{2}$$. The VC of SUS316L contacted with the zeolites decreased with increasing Cl$$^{-}$$ ion concentration and is slightly smaller than the VC in the bulk water. The contact with the zeolites causes the suppressant of increasing ESP under the irradiation. The contact with the zeolites can reduce probability in the localized corrosion for SUS316L.

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