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Journal Articles

Quasifree neutron knockout reaction reveals a small $$s$$-Orbital component in the Borromean nucleus $$^{17}$$B

Yang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; et al.

Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02

 Times Cited Count:21 Percentile:97.82(Physics, Multidisciplinary)

A quasifree ($$p$$,$$pn$$) experiment was performed to study the structure of the Borromean nucleus $$^{17}$$B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for $$1s_{1/2}$$ and $$0d_{5/2}$$ orbitals, and a surprisingly small percentage of 9(2)% was determined for $$1s_{1/2}$$. Our finding of such a small $$1s_{1/2}$$ component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in $$^{17}$$B. The present work gives the smallest $$s$$- or $$p$$-orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of $$s$$ or $$p$$ orbitals is not a prerequisite for the occurrence of a neutron halo.

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

Probing carbon edge exposure of iron phthalocyanine-based oxygen reduction catalysts by soft X-ray absorption spectroscopy

Niwa, Hideharu*; Saito, Makoto*; Kobayashi, Masaki*; Harada, Yoshihisa*; Oshima, Masaharu*; Moriya, Shogo*; Matsubayashi, Katsuyuki*; Nabae, Yuta*; Kuroki, Shigeki*; Ikeda, Takashi; et al.

Journal of Power Sources, 223, p.30 - 35, 2013/02

 Times Cited Count:18 Percentile:54.18(Chemistry, Physical)

To design non-platinum, inexpensive, but high performance carbon-based cathode catalysts for polymer electrolyte fuel cells, it is important to elucidate the active site for oxygen reduction reaction (ORR). However, it is difficult to directly identify the active site by applying conventional structural or electronic probes to such complex systems. Here, we used C 1${it s}$ X-ray absorption spectroscopy (XAS) to observe electronic structure of carbon in iron phthalocyanine-based catalysts, and found a signature of edge exposure below the $$pi^{ast}$$ edge, whose intensity is well correlated with the ORR activity. These results demonstrate that C 1${it s}$ XAS can be used to characterize the ORR activity of carbon-based cathode catalysts in terms of the edge exposure.

Journal Articles

Indirect contribution of transition metal towards oxygen reduction reaction activity in iron phthalocyanine-based carbon catalysts for polymer electrolyte fuel cells

Kobayashi, Masaki*; Niwa, Hideharu*; Saito, Makoto*; Harada, Yoshihisa*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Electrochimica Acta, 74, p.254 - 259, 2012/07

 Times Cited Count:52 Percentile:83.6(Electrochemistry)

The electronic structure of the residual metal atoms in FePc-based carbon catalysts, prepared by pyrolyzing a mixture of FePc and phenolic resin polymer at 800$$^{circ}$$C, before and after acid washing have been investigated using XAFS spectroscopy to clarify the role of Fe in the ORR activity. The decomposition analyses for the XAFS spectra reveal that the composition ratio of each Fe component is unaltered by the acid washing, indicating that the residual Fe components were removed by the acid washing irrespective of their chemical states. Because the oxygen reduction potential was approximately unchanged by the acid washing, the residual Fe itself does not seem to contribute directly to the ORR activity. The residual Fe can act as a catalyst to accelerate the growth of the sp$$^{2}$$ carbon network during pyrolysis. The results imply that light elements are components of the ORR active sites in the FePc-based carbon catalysts.

Journal Articles

Role of residual transition-metal atoms in oxygen reduction reaction in cobalt phthalocyanine-based carbon cathode catalysts for polymer electrolyte fuel cell

Kobayashi, Masaki*; Niwa, Hideharu*; Harada, Yoshihisa*; Horiba, Koji*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Journal of Power Sources, 196(20), p.8346 - 8351, 2011/10

 Times Cited Count:32 Percentile:69.85(Chemistry, Physical)

The electronic structure of Co atoms in CoPc-based carbon catalysts, which were prepared by pyrolyzing a mixture of CoPc and phenol resin polymer up to 1000$$^circ$$C, has been investigated using XAFS analysis and HXPES. The Co K XAFS spectra show that most of the Co atoms are in the metallic state and small quantities of oxidized Co components are present in the samples even after acid washing to remove Co atoms. Based on the difference in probing depth between XAFS and HXPES, it was found that after acid washing, the surface region with the aggregated Co clusters is primarily composed of metallic Co. Since the electrochemical properties remain almost unchanged even after the acid washing process, the residual metallic and oxidized Co atoms themselves will hardly contribute to the ORR activity of the CoPc-based carbon cathode catalysts, implying that the active sites of the CoPc-based catalysts primarily consist of light elements such as C and N.

Journal Articles

X-ray photoemission spectroscopy analysis of N-containing carbon-based cathode catalysts for polymer electrolyte fuel cells

Niwa, Hideharu*; Kobayashi, Masaki*; Horiba, Koji*; Harada, Yoshihisa*; Oshima, Masaharu*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; Miyata, Seizo*; et al.

Journal of Power Sources, 196(3), p.1006 - 1011, 2011/02

 Times Cited Count:85 Percentile:91.91(Chemistry, Physical)

We report on the electronic structure of three different types of N-containing carbon-based cathode catalysts for polymer electrolyte fuel cells observed by hard X-ray photoemission spectroscopy. C 1s spectra show the importance of $$sp^{2}$$ carbon network formation for the oxygen reduction reaction (ORR) activity. Samples having high oxygen reduction reaction activity in terms of oxygen reduction potential contain high concentration of graphite-like nitrogen. Based on a quantitative analysis of our results, the oxygen reduction reaction activity of the carbon-based cathode catalysts will be improved by increasing concentration of graphite-like nitrogen in a developed $$sp^{2}$$ carbon network.

Journal Articles

Enhanced catalytic activity of Carbon Alloy Catalysts codoped with boron and nitrogen for oxygen reduction reaction

Ikeda, Takashi; Boero, M.*; Huang, S.-F.*; Terakura, Kiyoyuki*; Oshima, Masaharu*; Ozaki, Junichi*; Miyata, Seizo*

Journal of Physical Chemistry C, 114(19), p.8933 - 8937, 2010/05

 Times Cited Count:59 Percentile:84.05(Chemistry, Physical)

Carbon Alloy Catalysts (CACs) have been attracting a growing interest as potential Pt-free electrode catalysts for polymer electrolyte fuel cell. In this computational study, we inspect possible oxygen adsorption and reduction processes on various models for exposed edges of these catalysts via first principles molecular dynamics. Our simulations suggest that the codoping of boron and nitrogen in CACs is a promising route to further enhancement of their catalytic activity with respect to both stability and reactivity.

Journal Articles

First-principles calculation of the electronic properties of graphene clusters doped with nitrogen and boron; Analysis of catalytic activity for the oxygen reduction reaction

Huang, S.-F.*; Terakura, Kiyoyuki*; Ozaki, Taisuke*; Ikeda, Takashi; Boero, M.*; Oshima, Masaharu*; Ozaki, Junichi*; Miyata, Seizo*

Physical Review B, 80(23), p.235410_1 - 235410_12, 2009/12

 Times Cited Count:165 Percentile:97.5(Materials Science, Multidisciplinary)

Recent studies suggest that the carbon-alloy catalyst with doped nitrogen may be a powerful candidate for cathode catalyst of fuel cell. In this paper, we aim to clarify the microscopic mechanisms of the enhancement in the catalyst activity caused by nitrogen doping using a simple graphene cluster model. We analyze modifications in the electronic structures and the energetical stability for some different configurations of N doping. We extend the analysis to the case of co-doping of nitrogen and boron and propose two possible scenarios explaining the further enhancement of catalytic activity by N and B co-doping.

Journal Articles

X-ray absorption analysis of nitrogen contribution to oxygen reduction reaction in carbon alloy cathode catalysts for polymer electrolyte fuel cells

Niwa, Hideharu*; Horiba, Koji*; Harada, Yoshihisa*; Oshima, Masaharu*; Ikeda, Takashi; Terakura, Kiyoyuki*; Ozaki, Junichi*; Miyata, Seizo*

Journal of Power Sources, 187(1), p.93 - 97, 2009/02

 Times Cited Count:419 Percentile:99.82(Chemistry, Physical)

The electronic structure of nitrogens introduced in various carbon-based cathode catalysts for a polymer electrolyte fuel cell (PEFC) has been investigated using X-ray absorption spectroscopy (XAS). The profile of the $$pi^{ast}$$ peaks at the pre-edge of the N 1s XAS spectra is used to determine the chemical states of nitrogens, which can be a marker of the oxygen reduction reaction (ORR) activity; it is found that catalysts that have relatively high amount of graphite-like nitrogen exhibit higher ORR activity than those having relatively high amount of pyridine-like nitrogen. We propose that effective doping of graphite-like nitrogen is a practical guideline for the synthesis of active carbon alloy catalysts.

Journal Articles

Carbon alloy catalysts; Active sites for oxygen reduction reaction

Ikeda, Takashi; Boero, M.*; Huang, S.-F.*; Terakura, Kiyoyuki*; Oshima, Masaharu*; Ozaki, Junichi*

Journal of Physical Chemistry C, 112(38), p.14706 - 14709, 2008/09

 Times Cited Count:436 Percentile:99.43(Chemistry, Physical)

Nitrogen-doped carbon-based catalysts are attracting a renovated interest as potential Pt-free electrode catalysts for polymer electrolyte fuel cell. In this computational study, we inspect possible oxygen adsorption and reduction processes on various models for the exposed edges of these catalysts. The dynamics of an O$$_{2}$$ molecule solvated in water, mimicking the cathode environment, shows that O$$_{2}$$ adsorption depends on the morphology and atomic structure of the system. We show that carbon alloys with N dopants at specific sites can exhibit a metal-free catalytic activity.

Journal Articles

In-core SCC growth behavior of type 304 stainless steel in BWR simulated high-temperature water at JMTR

Kaji, Yoshiyuki; Ugachi, Hirokazu; Tsukada, Takashi; Nakano, Junichi; Matsui, Yoshinori; Kawamata, Kazuo; Shibata, Akira; Omi, Masao; Nagata, Nobuaki*; Dozaki, Koji*; et al.

Journal of Nuclear Science and Technology, 45(8), p.725 - 734, 2008/08

 Times Cited Count:6 Percentile:41.87(Nuclear Science & Technology)

Irradiation assisted stress corrosion cracking (IASCC) is one of the critical concerns when stainless steel components have been in service in light water reactors for a long period. In-core IASCC growth tests have been carried out using the compact tension type specimens of type 304 stainless steel that had been pre-irradiated up to a neutron fluence level around 1$$times$$10$$^{25}$$n/m$$^{2}$$ in pure water simulated boiling water reactor (BWR) coolant condition at the Japan Materials Testing Reactor (JMTR). In order to investigate the effect of synergy of neutron/$$gamma$$ radiation and stress/water environment on IASCC growth rate, we performed ex-core IASCC tests on irradiated specimens at several dissolved oxygen contents environments under the same electrochemical potential condition. In this paper, results of the in-core SCC growth tests will be discussed and compared with the result obtained by ex-core tests from a viewpoint of the synergistic effects on IASCC.

Journal Articles

The H-Invitational Database (H-InvDB); A Comprehensive annotation resource for human genes and transcripts

Yamasaki, Chisato*; Murakami, Katsuhiko*; Fujii, Yasuyuki*; Sato, Yoshiharu*; Harada, Erimi*; Takeda, Junichi*; Taniya, Takayuki*; Sakate, Ryuichi*; Kikugawa, Shingo*; Shimada, Makoto*; et al.

Nucleic Acids Research, 36(Database), p.D793 - D799, 2008/01

 Times Cited Count:51 Percentile:73.21(Biochemistry & Molecular Biology)

Here we report the new features and improvements in our latest release of the H-Invitational Database, a comprehensive annotation resource for human genes and transcripts. H-InvDB, originally developed as an integrated database of the human transcriptome based on extensive annotation of large sets of fulllength cDNA (FLcDNA) clones, now provides annotation for 120 558 human mRNAs extracted from the International Nucleotide Sequence Databases (INSD), in addition to 54 978 human FLcDNAs, in the latest release H-InvDB. We mapped those human transcripts onto the human genome sequences (NCBI build 36.1) and determined 34 699 human gene clusters, which could define 34 057 protein-coding and 642 non-protein-coding loci; 858 transcribed loci overlapped with predicted pseudogenes.

Journal Articles

Present status of in-pile IASCC growth tests at JMTR

Kaji, Yoshiyuki; Ugachi, Hirokazu; Nakano, Junichi*; Matsui, Yoshinori; Kawamata, Kazuo; Tsukada, Takashi; Nagata, Nobuaki*; Dozaki, Koji*; Takiguchi, Hideki*

HPR-364, Vol.1 (CD-ROM), 10 Pages, 2005/10

Irradiation assisted stress corrosion cracking (IASCC) is one of the critical concerns when stainless steel components have been in service in light water reactors (LWRs) for a long period. In the research field of IASCC, mainly PIEs for irradiated materials have been carried out, because there are many difficulties on SCC tests under neutron irradiation. Hence as a part of the key techniques for in-pile SCC tests, we have embarked on a development of the test technique to obtain information concerning effects of applied stress level, water chemistry, irradiation conditions, etc. In this paper, we describe the developed several techniques, especially control of loading on specimens, monitoring technique of crack propagation and so on, and the present status of in-pile IASCC growth tests using pre-irradiated materials at JMTR.

Journal Articles

Development of test techniques for in-pile SCC initiation and growth tests and the current status of in-pile testing at JMTR

Ugachi, Hirokazu; Kaji, Yoshiyuki; Nakano, Junichi*; Matsui, Yoshinori; Kawamata, Kazuo; Tsukada, Takashi; Nagata, Nobuaki*; Dozaki, Koji*; Takiguchi, Hideki*

Proceedings of 12th International Conference on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors (CD-ROM), p.319 - 325, 2005/00

Irradiation assisted stress corrosion cracking (IASCC) is one of the critical concerns when stainless steel components have been in service in light water reactors (LWRs) for a long period. In the research field of IASCC, mainly PIEs for irradiated materials have been carried out, because there are many difficulties on SCC tests under neutron irradiation. Hence as a part of the key techniques for in-pile SCC tests, we have embarked on a development of the test technique to obtain information concerning effects of applied stress level, water chemistry, irradiation conditions, etc. In this conference, we describe the developed several techniques, especially control of loading on specimens, monitoring technique of crack initiation, propagation and water chemistry, and the current status of in-pile SCC tests using thermally sensitized materials at JMTR.

JAEA Reports

Fabrication of saturated temperature capsule for IASCC study

Ishikawa, Kazuyoshi; Kikuchi, Taiji; Isozaki, Futoshi*; Inoue, Hiromi; Oba, Toshihiro; Matsui, Yoshinori; Saito, Takashi; Nakano, Junichi; Tsuji, Hirokazu

JAERI-Tech 2002-061, 69 Pages, 2002/08

JAERI-Tech-2002-061.pdf:12.21MB

Study of irradiation assisted stress corrosion cracking (IASCC) is an important subject for the plant life assessment and extension of the light water reactors (LWRs). It is necessary that initiation mechanism of IASCC should be made clear under combined effect of irradiation, environment and stress in order to understand IASCC phenomena. Under the existing circumstance, Saturated Temperature Capsule (SATCAP) were fabricated for the irradiation test of IASCC studies in Japan Material Testing Reactor (JMTR). SATCAP is the irradiation rig to irradiate materials in high pressure water of controlled chemistry and temperature simulating Boiling water reactors (BWRs) core environment from the new water feelding system of out-of-pile. This report describes (1) investigation of technical problems for the design and fabrication of SATCAP, (2) the tests results of the problems and (3) fabrication and inspection of SATCAP.

JAEA Reports

None

Narita, Osamu; Ishida, Junichiro; Katagiri, Hiromi; Hayashi, Naomi; Miyagawa, Naoto; Watanabe, Hitoshi; Kobayashi, Mitsuru; Namiki, Atsushi; Sumiya, Shuichi; ; et al.

PNC TN8420 89-009, 238 Pages, 1989/08

PNC-TN8420-89-009.pdf:4.32MB

None

Oral presentation

Exploration of active sites of carbon alloy catalysts via first principles molecular dynamics

Ikeda, Takashi; Boero, M.*; Terakura, Kiyoyuki*; Oshima, Masaharu*; Ozaki, Junichi*

no journal, , 

no abstracts in English

Oral presentation

Investigation of crack initiation behavior using pre-irradiated austenitic stainless steel at JMTR

Tsukada, Takashi; Ugachi, Hirokazu; Kaji, Yoshiyuki; Miwa, Yukio; Nakano, Junichi; Matsui, Yoshinori; Endo, Shinya; Kato, Yoshiaki; Nagata, Nobuaki*; Dozaki, Koji*; et al.

no journal, , 

Irradiation Assisted Stress Corrosion Cracking (IASCC) has been regarded in recent years as the matter that is related to the reliability for core components of LWRs. The in-pile IASCC initiation tests were performed using of uniaxial constant load specimens pre-irradiated to about 5$$times$$10$$^{24}$$n/m$$^{2}$$ and 1$$times$$10$$^{25}$$n/m$$^{2}$$ at JMTR under the simulated BWR core condition. From the results of in-pile and out-of-pile tests of the irradiated specimens, we confirmed that any remarkable acceleration effect of synergy of neutron/$$gamma$$ radiation and stress/water environment on SCC initiation results was not observed under the test condition of this study. On the surface of in-pile test specimen, a micro crack was observed on the surface of specimen, and it was considered to be an initiation of SCC besed on the results of out-of-pile experiments.

Oral presentation

Catalytic activity of carbon alloy catalysts for oxygen reduction reactions via first principles molecular dynamics

Ikeda, Takashi; Boero, M.*; Huang, S.-F.*; Terakura, Kiyoyuki*; Oshima, Masaharu*; Ozaki, Junichi*; Miyata, Seizo*

no journal, , 

no abstracts in English

Oral presentation

Activity for oxygen reduction reaction of carbon nano-onion prepared from nano-diamond

Kannari, Naokatsu*; Ozaki, Junichi*; Yamamoto, Shunya; Hakoda, Teruyuki; Yamaki, Tetsuya

no journal, , 

no abstracts in English

22 (Records 1-20 displayed on this page)