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Nakamura, Yuki*; Kojima, Yoshihiro*; Yamashita, Takuya; Shimomura, Kenta; Mizokami, Shinya
Journal of Nuclear Science and Technology, 62(12), p.1226 - 1230, 2025/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Saha, P. K.; Harada, Hiroyuki; Tamura, Fumihiko; Okabe, Kota; Yoshimoto, Masahiro; Shobuda, Yoshihiro; Okita, Hidefumi; Kojima, Kunihiro; Nakanoya, Takamitsu; Hatakeyama, Shuichiro; et al.
Physical Review Accelerators and Beams (Internet), 28(7), p.074201_1 - 074201_23, 2025/07
Times Cited Count：1 Percentile：59.26(Physics, Nuclear)Nagai, Takayuki; Okamoto, Yoshihiro; Shibata, Daisuke*; Kojima, Kazuo*; Hasegawa, Takehiko*; Sato, Seiichi*; Fukaya, Akane*; Hatakeyama, Kiyoshi*
JAEA-Research 2024-014, 54 Pages, 2025/02
JAEA-Research-2024-014.pdf:7.02MB
XAFS measurements in the soft X-ray region are suitable for evaluating the chemical state of the surface layer of a measurement sample because the X-ray transmittance is low. In this study, the purpose of the study was to confirm the difference between the coagulated surface layer and the inside of the simulated waste glasses by measuring the K-edge of the glass constituent elements boron, oxygen, sodium, and silicon, and the L
edge of the waste component cerium. As a result, the B K-edge XANES spectra showed that the proportion of B-O tetracoordinate sp
structures (BO
) on the surface layer of the coagulated glass samples was higher than that on the cut surface inside the glass samples, which is expected to improve the water resistance of the coagulated surface. On the other hand, the O K-edge XANES spectra suggested that the O abundance in the coagulated surface layer was lower than that in the cut surface inside the glass samples, and that alkali metal elements may be concentrated in the coagulated surface layer. However, no difference was observed in the Na K-edge XANES spectra between the coagulated surface layer and the cut surface, and no difference was observed in the Si K-edge XANES spectra between the solidified surface and the inside of glass samples. In addition, the Ce L-edge XANES spectra confirmed that the Ce valence in the surface layer of coagulated glass samples were oxidized compared to the inside of glass samples.
Nakamura, Yuki*; Kojima, Yoshihiro*; Yamashita, Takuya; Shimomura, Kenta; Mizokami, Shinya
Proceedings of 14th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation, and Safety (NUTHOS-14) (Internet), 12 Pages, 2024/08
Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Shibata, Daisuke*; Kojima, Kazuo*; Hasegawa, Takehiko*; Sato, Seiichi*; Fukaya, Akane*; Hatakeyama, Kiyoshi*
JAEA-Research 2023-004, 45 Pages, 2023/09
JAEA-Research-2023-004.pdf:6.07MB
The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, simulated waste glass samples were prepared and the chemical state regarding boron (B), silicon (Si) and waste elements of iron (Fe), cesium (Cs) were estimated by using XAFS measurement in soft X-ray region. To understand the chemical stability of simulated waste glasses, XANES spectra of B K-edge, Fe L, L
-edge, and Cs M
, M-edge were measured on the glass surface exposed to the leachate. As a result, it was found that the glass surface exposed to the leachate was changed and it was difficult to obtain a clear XANES spectrum. From the B K-edge XANES spectra on glass surfaces exposed to the leachate, an increase in three-coordination of B-O (BO) and a decrease in four-coordination of B-O (BO) were observed compared to the glass surfaces before immersion. The XANES spectra of Fe L, L-edge, and Cs M, M-edge show that as the exposure time in the leachate increases, the Cs present on the glass surface dissolves into the leachate. The XANES spectra of Si K-edge were measured on simulated waste glass surfaces before immersion, and it was confirmed that the change in XANES spectra given by NaO concentration had a larger effect than the waste component concentration.
Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Kojima, Kazuo*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*
JAEA-Research 2022-008, 37 Pages, 2022/10
JAEA-Research-2022-008.pdf:5.27MB
The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, borosilicate glass frit and simulated waste glass samples were prepared and the chemical state regarding boron (B), silicon (Si) and waste elements of iron (Fe), cesium (Cs) were estimated by using XAFS measurement in soft X-ray region. Following results were obtained by XAFS measurements of simulated waste glass surfaces after immersion test to investigate the long chemical stability. (1) As the leaching time of glass samples in immersion test passed, the Cs M, M-edge XANES spectra disappeared and the Fe L, L-edge spectra changed. (2) A new compound was formed on the sample surface after the immersion test, and these changes in the surface state were confirmed by Raman spectroscopy. However, it became difficult to obtain a clear B K-edge XANES spectrum by forming a compound on glass surfaces. The Si K-edge XANES spectra of borosilicate glass frits with different NaO content were measured, and following was confirmed. (1) As the NaO concentration increases in borosilicate glass frit, the K-edge peak of Si shifts to the low energy side. (2) The intensity of the Si K-edge peak is maximum when the NaO content in glass frits was about 7wt%.
Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Ota, Toshiaki*; Kojima, Kazuo*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*
JAEA-Research 2021-010, 62 Pages, 2022/01
JAEA-Research-2021-010.pdf:6.05MB
The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, borosilicate glass frit and simulated waste glass samples were prepared and the local structure and chemical state regarding boron(B), oxygen(O), silicon(Si) and waste elements of iron(Fe), cesium(Cs) were estimated by using XAFS measurement in soft X-ray region. Following results were obtained by XAFS measurements of prepared glass frit and simulated waste glass samples: (1) The effect of NaO concentration on B-O coordination structure is greater than that of the waste elements concentration. (2) The height of pre-edge by O K-edge spectrum depends on the concentration of first transition elements such as Fe in glass samples. Following results were obtained by XAFS measurements of simulated waste glass samples after immersion test to investigate the long chemical stability. (1) A new compound was formed on the sample surface after the immersion test, and changes in the surface state were confirmed by Raman spectroscopy. (2) Cs on the sample surface after immersion test dissolves into the leaching solution. The Si K-edge XANES spectra of borosilicate glass frits and simulated waste glass samples included lanthanides oxide were measured, and following was confirmed. (1) As the NaO concentration increases in borosilicate glass frit, the K-edge peak of Si shifts to the low energy side. (2) The peak height of the K-edge of Si differs depending on the kind of lanthanide.
Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Ota, Toshiaki*; Kojima, Kazuo*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*
JAEA-Research 2020-009, 48 Pages, 2020/09
JAEA-Research-2020-009.pdf:4.53MB
The local structure of glass-forming elements and waste elements in waste glass varies with its chemical composition. In this study, borosilicate glass frit and simulated waste glass samples were prepared and the local structure and chemical state regarding boron (B), oxygen (O), and waste elements of cerium (Ce), cesium (Cs) were estimated by using XAFS measurement in soft X-ray region. Following results were obtained by XAFS measurements of prepared glass frit and simulated waste glass samples: (1) The existence ratio of four coordinate sp structure (BO) tends to increase with increasing NaO content in glass samples. (2) The height of a pre-edge which appears by K-edge XANES spectrum of O is so high that the Fe content in glass samples. Following results were obtained by XAFS measurements of simulated waste glass samples after immersion test to investigate long chemical stability. (1) The existence ratio of four coordinate sp structure (BO) increases by immersion test. (2) Ce which exists in the surface layer is oxidized by immersion test, and much of Cs in surface layer is lost after leach testing. Even if the glass frit form (fiber cartridge or beads) and manufacturing method were changed and a glass sample of the similar chemical composition was prepared, these observed Raman spectra of samples were different.
Nb and NiTa intermetallic compoundsKojima, Hiroshi*; Kaneno, Yasuyuki*; Ochi, Masaaki*; Semboshi, Satoshi*; Hori, Fuminobu*; Saito, Yuichi*; Ishikawa, Norito; Okamoto, Yoshihiro; Iwase, Akihiro*
Materials Transactions, 58(5), p.739 - 748, 2017/05
Times Cited Count：7 Percentile：28.54(Materials Science, Multidisciplinary)Bulk samples of NiNb and NiTa intermetallic compounds were irradiated with 16 MeV Au, 4.5 MeV Ni, 4.5 MeV Al, 200 MeV Xe and 1.0 MeV He ions, and the change in near-surface lattice structure was investigated by means of the grazing incidence X-ray diffraction (GIXD)and EXAFS. The NiNb and NiTa lattice structures transform from the ordered structures (orthorhombic and monoclinic structures for NiNb and NiTa, respectively) to the amorphous state by the Au, Ni, Al and Xe ion irradiations. Irrespective of such heavy ion species or energies, the lattice structure transformation to the amorphous state almost correlate with the density of energy deposited through elastic collisions.
Nb and NiTa intermetallic compounds induced by energetic ion beam irradiationKojima, Hiroshi*; Yoshizaki, Hiroaki*; Kaneno, Yasuyuki*; Semboshi, Satoshi*; Hori, Fuminobu*; Saito, Yuichi; Okamoto, Yoshihiro; Iwase, Akihiro*
Nuclear Instruments and Methods in Physics Research B, 372, p.72 - 77, 2016/04
Times Cited Count：13 Percentile：70.34(Instruments & Instrumentation)NiNb and NiTa intermetallic compounds, which show the complicated lattice structures were irradiated with 16 MeV Au
ions at room temperature. The X-ray diffraction measurement revealed that the lattice structure of these intermetallic compounds changed from the ordered structures to the amorphous state by the ion irradiation. The irradiation-induced amorphization caused the increase in Vickers hardness. The result was compared with our previous results for NiAl and NiV, and was discussed in terms of the intrinsic lattice structures of the samples.
Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Kugo, Teruhiko; Ando, Masaki; Kojima, Kensuke; Fukushima, Masahiro; Mori, Takamasa; Nakano, Yoshihiro; Okajima, Shigeaki; Kitada, Takanori*; Takeda, Toshikazu*
Journal of Nuclear Science and Technology, 45(4), p.288 - 303, 2008/04
Times Cited Count：6 Percentile：37.88(Nuclear Science & Technology)The effectiveness of the extended bias factor methods, the LC and PE methods, is numerically investigated by applying them to a breeding light water reactor core as a target core with use of FCA-XXII-1 critical experiments. The present study numerically verifies the features of the extended bias factor methods. Both the methods can improve the prediction accuracy the most by using all the experiments. The PE method always improves the prediction accuracy with any combination of experiments. The PE method is always superior to the LC method for improvement of the prediction accuracy. From the present study, the followings are found. The experiments on multiplication factor are more applicable to a reaction rate ratio of 
U capture to 
Pu fission (C28/F49) of the target core than the experiments on C28/F49. Combinations of the experiments on multiplication factor is more effective to a void reactivity of the target core than those of the experiments on void reactivity though those on void reactivity are superior to those on multiplication factors in the case of using a single experiment. From these results, we conclude that the experiments on multiplication factor are more effective than the other experiments for all the neutronic characteristics of the target core. From these results, it is concluded that the PE method is promising to complement full mockup experiments for various future nuclear systems by using a number of existing and future benchmark experiments.
Sono, Hiroki; Ono, Akio; Kojima, Takuji; Yamane, Yoshihiro*
Journal of Nuclear Science and Technology, 44(1), p.43 - 53, 2007/01
Times Cited Count：2 Percentile：17.85(Nuclear Science & Technology)A practical method is proposed for retrospective estimation of the spatial dose distribution and the number of fissions in a typical criticality accident. In this method, two kinds of low-fading and tissue-equivalent dosimeters are used as area dosimeters: an alanine dosimeter and a thermoluminescence dosimeter made of enriched lithium tetra borate. The procedure of the method consists of four parts: (1) dosimetry using area dosimeters (2) search for the center of the radiation source, (3) estimation of the spatial dose distribution, and (4) estimation of the number of fissions. Dosimetry of criticality accident situations simulated at the TRACY facility demonstrates the practicability of the method. Although a post-hoc analysis in principle, this method gives useful information on the magnitude and hazard level of the accident to determine the strategy of radiation emergency medicine and other post-accident measures if the area dosimeters are retrieved immediately after the accident.
Sono, Hiroki; Ono, Akio*; Kojima, Takuji; Takahashi, Fumiaki; Yamane, Yoshihiro*
Journal of Nuclear Science and Technology, 43(3), p.276 - 284, 2006/03
Times Cited Count：1 Percentile：9.39(Nuclear Science & Technology)For a study on the applicability of a personal dosimetry method to criticality accident dosimetry, an assessment of the human body surface and internal dose estimations was performed by experimental and computational simulations. The experimental simulation was carried out in a criticality accident situation at the TRACY facility. The neutron and 
-ray absorbed doses in muscle tissue were separately estimated by a dosimeter set of an alanine dosimeter and a thermoluminescence dosimeter made of enriched lithium tetra borate with a phantom. The computational simulation was conducted with a Monte Carlo code taking account of dose components of neutrons, prompt -rays and delayed -rays. The computational simulation was ascertained to be valid by comparison between the calculated dose distributions in the phantom and the measured ones. The assessment based on the experimental and computational simulations confirmed that the personal dosimetry using the dosimeter set provided a first estimation of the body surface and internal doses with precision.
Taguchi, Mitsumasa; Zennyoji, Yoshihiro*; Takigami, Machiko*; Baldacchino, G.*; Kimura, Atsushi; Hiratsuka, Hiroshi*; Namba, Hideki; Kojima, Takuji
Radiation Physics and Chemistry, 75(5), p.564 - 571, 2006/03
Times Cited Count：6 Percentile：39.61(Chemistry, Physical)The suspended fine particles formed in aqueous phenol solution under high dose irradiation were studied using the MeV electron beam and 
Co -ray irradiations. The fine particle's size was 100-800 nm in diameter and became bigger at higher dose and lower dose rate. The distributions of the particle size became narrower for irradiation at higher dose rate. The fine particles were regarded to consist of molecules of about 1.9
10
molecular weight.
Kasahara, Mikio*; Ma, C.-J.*; Okumura, Motonori*; Kojima, Takuji; Hakoda, Teruyuki; Taguchi, Mitsumasa; Sakai, Takuro; Ohara, Yoshihiro
JAEA-Review 2005-001, TIARA Annual Report 2004, p.293 - 295, 2006/01
Artificial cloud generation experiment was performed using a huge vertical pit located in Kamaishi iron-copper mine to investigate the characteristics of cloud. The physical and chemical properties of individual cloud droplets were examined by microscopic analysis at Kyoto university and micro-PIXE analysis at TIARA. The process of growth of cloud was clarified based on the result on droplet size, its distribution, droplet number concentration, and the change in distribution of chlorine in droplet as the function of size.
Kasahara, Mikio*; Ma, C.-J.*; Okumura, Motonori*; Kojima, Takuji; Hakoda, Teruyuki; Taguchi, Mitsumasa; Sakai, Takuro; Ohara, Yoshihiro
JAERI-Review 2004-025, TIARA Annual Report 2003, p.256 - 258, 2004/11
As the source of Asian dust particles, the sands at four different desert areas in China were to be the target of bulk and single analyses by means of PIXE and micro-PIXE analyses, respectively. The physical properties of desert sands like morphology, color, and size were basically determined. Also the chemical characteristics of bulk sands of each desert were specified as the relative elemental mass. The elemental maps and spectra for individual sands allow us to understand the nature of individual sands. Consequently, the physicochemical properties of desert sands obtained from this study can be helpful to understand what kinds of man-made pollutants and sea-salts are incorporated into natural Asian dust particles.
Ohara, Yoshihiro; Akiba, Masato; Araki, Masanori; Dairaku, Masayuki; Hanada, Masaya; Inoue, Takashi; Kojima, Hiroaki; Kuriyama, Masaaki; ; Matsuoka, Mamoru; et al.
JAERI-M 90-154, 119 Pages, 1990/09
no abstracts in English
ion beamKojima, Hiroaki; Hanada, Masaya; Inoue, Takashi; ; Ohara, Yoshihiro; Okumura, Yoshikazu; Ohara, Hiroshi; Seki, Masahiro; Watanabe, Kazuhiro
Proc. of the 13th Symp. on Ion Sources and Ion-Assisted Technology,Vol. 1, 4 Pages, 1990/06
no abstracts in English
Watanabe, Kazuhiro; Hanada, Masaya; Inoue, Takashi; Kojima, Hiroaki; ; Ohara, Yoshihiro; Okumura, Yoshikazu
Proc. of the 13th Symp. on Ion Sources and Ion-Assisted Technology,Vol. 1, 4 Pages, 1990/06
no abstracts in English
