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Journal Articles

Unusual redox behavior of ruthenocene confined in the micropores of activated carbon

Itoi, Hiroyuki*; Ninomiya, Takeru*; Hasegawa, Hideyuki*; Maki, Shintaro*; Sakakibara, Akihiro*; Suzuki, Ryutaro*; Kasai, Yuto*; Iwata, Hiroyuki*; Matsumura, Daiju; Owada, Mao*; et al.

Journal of Physical Chemistry C, 124(28), p.15205 - 15215, 2020/07

 Times Cited Count:8 Percentile:40.97(Chemistry, Physical)

Journal Articles

Damped soft phonons and diffuse scattering in (Bi$$_{1/2}$$Na$$_{1/2}$$)TiO$$_{3}$$

Matsuura, Masato*; Iida, Hiroyuki*; Hirota, Kazuma*; Owada, Kenji; Noguchi, Yuji*; Miyayama, Masaru*

Physical Review B, 87(6), p.064109_1 - 064109_10, 2013/02

 Times Cited Count:28 Percentile:74.56(Materials Science, Multidisciplinary)

Neutron-scattering studies of (Bi$$_{1/2}$$Na$$_{1/2}$$)TiO$$_{3}$$ (BNT) have been performed to elucidate the microscopic mechanism of the broad maximum in the temperature dependence of the dielectric constant at Tm $$sim$$ 600 K and the reduction in the piezoelectric properties above the depolarization temperature, 460 $$sim$$ 480 K. We observed diffuse scattering near the $$Gamma$$ point below 700 K, which competes with the superlattice peak at the M point of the tetragonal phase but coexists with the superlattice peak at the R point of the rhombohedral phase. The diffuse scattering shows an anisotropic Q shape extending along the $$<$$100$$>$$ direction transverse to the scattering vector Q, which is explained by atomic shifts bridging the tetragonal and rhombohedral structures. We propose that the broad maximum in the dielectric constant is associated with a diffusive first-order transition between the competing tetragonal and rhombohedral phases. In addition, we found that the diffuse scattering is reduced for single crystals grown under high oxygen pressure, which suggests an analogy with the central peak in hydrogen-reduced SrTiO$$_{3}$$. Inelastic neutron scattering near the $$Gamma$$ point reveals a heavily overdamped soft mode similar to those reported in lead-based relaxors, the "waterfall" feature. Moreover, a damped soft transverse acoustic mode is observed for the $$<$$100$$>$$ direction as the anisotropic diffuse scattering, indicating phase instabilities with the same origin as that of the diffuse scattering. The recovery of the soft mode is observed near the depolarization temperature, which coincides with the disappearance of the superlattice peak at the M point. These results indicate that the depolarization and the waterfall feature originate in the dynamic nature of ferroelectric clusters in the coexisting tetragonal/rhombohedral phase.

JAEA Reports

Conceptual design of multipurpose compact research reactor; Annual report FY2010 (Joint research)

Imaizumi, Tomomi; Miyauchi, Masaru; Ito, Masayasu; Watahiki, Shunsuke; Nagata, Hiroshi; Hanakawa, Hiroki; Naka, Michihiro; Kawamata, Kazuo; Yamaura, Takayuki; Ide, Hiroshi; et al.

JAEA-Technology 2011-031, 123 Pages, 2012/01

JAEA-Technology-2011-031.pdf:16.08MB

The number of research reactors in the world is decreasing because of their aging. However, the planning to introduce the nuclear power plants is increasing in Asian countries. In these Asian countries, the key issue is the human resource development for operation and management of nuclear power plants after constructed them, and also the necessity of research reactor, which is used for lifetime extension of LWRs, progress of the science and technology, expansion of industry use, human resources training and so on, is increasing. From above backgrounds, the Neutron Irradiation and Testing Reactor Center began to discuss basic concept of a multipurpose low-power research reactor for education and training, etc. This design study is expected to contribute not only to design tool improvement and human resources development in the Neutron Irradiation and Testing Reactor Center but also to maintain and upgrade the technology on research reactors in nuclear power-related companies. This report treats the activities of the working group from July 2010 to June 2011 on the multipurpose low-power research reactor in the Neutron Irradiation and Testing Reactor Center and nuclear power-related companies.

JAEA Reports

Safety demonstration test using the High Temperature Engineering Test Reactor (HTTR); Cold test of the loss of forced cooling

Shinohara, Masanori; Yanagi, Shunki; Tochio, Daisuke; Shimazaki, Yosuke; Nojiri, Naoki; Owada, Hiroyuki; Sato, Nao; Sagawa, Hiroshi; Umeda, Masayuki

JAEA-Technology 2011-029, 39 Pages, 2011/12

JAEA-Technology-2011-029.pdf:3.03MB

JAEA plans and performs the safety demonstration test using the HTTR to develop High Temperature Gas Reactor technologies. Cold test of the loss of forced cooling was conducted prior to the safety demonstration test, to check test procedure and plant behavior. Cold test consists of two phases, Phase1, 1 or 2 Vessel Cooling System (VCS) terminates, in the Phase2, all 3 Gas circulators and 1 VCS terminates. Cold test could confirm test process, and obtain data necessary to analysis and 2-dimensional horizontal sectional model analysis was verified to simulate actual measurement value.

Journal Articles

Decommissioning program and future plan for Research Hot Laboratory, 2

Koya, Toshio; Nozawa, Yukio; Hanada, Yasushi; Ono, Katsuto; Kanazawa, Hiroyuki; Nihei, Yasuo; Owada, Isao

Dekomisshoningu Giho, (42), p.41 - 48, 2010/09

The Research Hot Laboratory (RHL) in Japan Atomic Energy Agency (JAEA) had been contributed to R&D program for fuels and nuclear materials in or out of JAEA. However, the decommissioning work of RHL has been started on April 2003 as the rationalization program for decrepit facilities in former Tokai institute. This work will be progressing, dismantling the lead cells and decontamination of concrete caves then release in the regulation of controlled area. The partial area of RHL will be used for the central storage of un- irradiated fuel and for temporary storage of radioactive device generated by J-PARC. The 18 lead cells had been dismantled and the preparing work for remained 20 lead cells has been finished including the removal of the applause from the cells, survey of the contamination revel in the lead cells and prediction of radio active waste. The future plan of decommissioning work has been prepared to incarnate the basic vision and dismantling procedure.

Journal Articles

Resonant magnetic X-ray diffraction study on the successive metamagnetic transitions of TbB$$_4$$ up to 30T

Inami, Toshiya; Owada, Kenji; Matsuda, Yasuhiro*; Ouyang, Z. W.*; Nojiri, Hiroyuki*; Matsumura, Takeshi*; Okuyama, Daisuke*; Murakami, Yoichi*

Journal of Physics; Conference Series, 211, p.012010_1 - 012010_6, 2010/02

 Times Cited Count:3 Percentile:75.92

Journal Articles

XMCD spectroscopy on valence fluctuating and heavy fermion compounds in very high magnetic fields up to 40 T

Matsuda, Yasuhiro*; Her, J. L.*; Inami, Toshiya; Owada, Kenji; Ouyang, Z. W.*; Okada, Kyoko*; Nojiri, Hiroyuki*; Mitsuda, Akihiro*; Wada, Hirofumi*; Yoshimura, Kazuyoshi*; et al.

Journal of Physics; Conference Series, 190, p.012019_1 - 012019_6, 2009/11

 Times Cited Count:7 Percentile:85.24

Journal Articles

X-ray magnetic circular dichroism of a valence fluctuating state in Eu at high magnetic fields

Matsuda, Yasuhiro*; Ouyang, Z. W.*; Nojiri, Hiroyuki*; Inami, Toshiya; Owada, Kenji; Suzuki, Motohiro*; Kawamura, Naomi*; Mitsuda, Akihiro*; Wada, Hirofumi*

Physical Review Letters, 103(4), p.046402_1 - 046402_4, 2009/07

 Times Cited Count:53 Percentile:87.17(Physics, Multidisciplinary)

X-ray magnetic circular dichroism (XMCD) at the Eu L edge in two compounds exhibiting valence fluctuation, namely EuNi$$_2$$(Si$$_{0.18}$$Ge$$_{0.82}$$)$$_2$$ and EuNi$$_2$$P$$_2$$, has been investigated at high magnetic fields of up to 40T. A distinct XMCD peak corresponding to the trivalent state (Eu$$^{3+}$$), whose ground state is nonmagnetic (J = 0), was observed in addition to the main XMCD peak corresponding to the magnetic (J = 7/2) divalent state (Eu$$^{2+}$$). This result indicates that the 5$$d$$ electrons belonging to both valence states are magnetically polarized. It was also found that the ratio $$P$$$$_{5d}$$(3+)/$$P$$$$_{5d}$$(2+) between the polarization of 5$$d$$ electrons($$P$$$$_{5d}$$) in the Eu$$^{3+}$$ state and that of Eu$$^{2+}$$ depends on the material. The possible origin of the XMCD and an explanation of the material dependence of $$P$$$$_{5d}$$(3+)/$$P$$$$_{5d}$$(2+) are discussed in terms of hybridization between the conduction electrons and the f electrons.

JAEA Reports

Handling of HTTR second driver fuel elements in assembling and storage working

Tomimoto, Hiroshi; Kato, Yasushi; Owada, Hiroyuki; Sato, Nao; Shimazaki, Yosuke; Kozawa, Takayuki; Shinohara, Masanori; Hamamoto, Shimpei; Tochio, Daisuke; Nojiri, Naoki; et al.

JAEA-Technology 2009-025, 29 Pages, 2009/06

JAEA-Technology-2009-025.pdf:21.78MB

The first driver fuel of the HTTR (High Temperature Engineering test Reactor) was loaded in 1998 and the HTTR reached first criticality state in the same year. The HTTR has been operated using the first driver fuel for a decade. In Fuel elements assembling, 4770 of fuel rods which consist of 12 kinds of enrichment uranium are loaded into 150 fuel graphite blocks for HTTR second driver fuel elements. Measures of prevention of fuel rod miss loading, are employed in fuel design. Additionally, precaution of fuel handling on assembling are considered. Reception of fuel rods, assembling of fuel elements and storage of second driver fuels in the fresh fuel storage rack in the HTTR were started since June, 2008. Assembling, storage and pre-service inspection were divided into three parts. The second driver fuel assembling was completed in September, 2008. This report describes concerns of fuel handling on assembling and storage work for the HTTR fuel elements.

Journal Articles

Resonant magnetic X-ray diffraction study on successive metamagnetic transitions in TbB$$_4$$

Inami, Toshiya; Owada, Kenji; Matsuda, Yasuhiro*; Ouyang, Z. W.*; Nojiri, Hiroyuki*; Matsumura, Takeshi*; Okuyama, Daisuke*; Murakami, Yoichi*

Journal of the Physical Society of Japan, 78(3), p.033707_1 - 033707_4, 2009/03

 Times Cited Count:16 Percentile:65.84(Physics, Multidisciplinary)

JAEA Reports

Ultrasonic test results for the reactor pressure vessel of the HTTR; Longitudinal welding line of bottom dome

Nojiri, Naoki; Owada, Hiroyuki; Kato, Yasushi

JAEA-Technology 2008-045, 38 Pages, 2008/06

JAEA-Technology-2008-045.pdf:6.95MB

This paper describes the inspection method, the measured area, etc. of the ultrasonic test of the in-service inspection (ISI) for welding lines of the reactor pressure vessel of the HTTR and the inspection results of the longitudinal welding line of the bottom dome. The pre-service inspection (PSI) results for estimation of occurrence and progression of defects to compare the ISI results is described also.

Journal Articles

High-magnetic-field X-ray absorption spectroscopy of field-induced valence transition in EuNi$$_2$$(Si$$_{1-x}$$Ge$$_x$$)$$_2$$

Matsuda, Yasuhiro*; Inami, Toshiya; Owada, Kenji; Murata, Yuto*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Mitsuda, Akihiro*; Wada, Hirofumi*; Miyazaki, Hiroshi*; Harada, Isao*

Journal of the Physical Society of Japan, 77(5), p.054713_1 - 054713_7, 2008/05

 Times Cited Count:25 Percentile:74.48(Physics, Multidisciplinary)

The magnetic-field-induced valence transition in EuNi$$_2$$(Si$$_{1-x}$$Ge$$_x$$)$$_2$$ (x=0.82, 0.85) has been studied by X-ray absorption spectroscopy at low temperatures. The field dependence of the Eu valence is directly observed for the first time. We find a significant decrease in the valences at high magnetic fields above 40 T. The valence of Eu changes from v = 2.75 at a zero field to v = 2.33 at 40 T for x = 0.82. The results are analyzed using a theoretical model. The hybridization parameter V between the Eu$$^{2+}$$ and Eu$$^{3+}$$ states and the energy separation $$Delta$$$$E$$ are determined, which are crucial for quantum mechanical mixing.

Journal Articles

Devil's flower resulting from a successive charge disproportionation of NaV$$_{2}$$O$$_{5}$$; Understanding of the details of the Ising spin and the competitive interactions which made the devil's flower bloom

Owada, Kenji; Fujii, Yasuhiko; Muraoka, Jiro*; Nakao, Hironori*; Murakami, Yoichi*; Noda, Yukio*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Shobu, Takahisa; Isobe, Masahiko*; et al.

Hoshako, 21(2), p.87 - 96, 2008/03

Devil's flower has been found in a temperature-pressure phase diagram of NaV$$_{2}$$O$$_{5}$$, which shows a charge disproportionation (CD) at ambient pressure. By a complementary use of an X-ray structural analysis and a resonant X-ray diffraction, which is sensitive to CD, we have investigated the structural relationship between two ground states appeared in lower and higher pressure regions including the charge arrangements. It has been clarified that two equivalent types of charge arrangement in CD correspond to the Ising variable in NaV$$_{2}$$O$$_{5}$$. The atomic shifts are regarded as linearly coupled to the Ising spins. The results lead us to the conclusion that it is the first time that the devil's flower blooms in a charge-disproportionation system. The results also lead us to a hypothesis that the competitive interactions between a Ising spins may result from the Ising spin-phonon coupling.

Journal Articles

Direct observation of field-induced variant transformation in Fe$$_3$$Pt using pulsed magnetic field X-ray diffraction

Ouyang, Z. W.*; Matsuda, Yasuhiro*; Nojiri, Hiroyuki*; Inami, Toshiya; Owada, Kenji; Tsubota, Masami*; Sakon, Takuo*; Fukuda, Takashi*; Kakeshita, Tomoyuki*

Journal of Applied Physics, 102(11), p.113917_1 - 113917_6, 2007/12

 Times Cited Count:1 Percentile:5.43(Physics, Applied)

Journal Articles

Structural relations between two ground states of NaV$$_{2}$$O$$_{5}$$ under high pressure; A Synchrotron X-ray diffraction study

Owada, Kenji; Fujii, Yasuhiko; Muraoka, Jiro*; Nakao, Hironori*; Murakami, Yoichi; Noda, Yukio*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Shobu, Takahisa; Isobe, Masahiko*; et al.

Physical Review B, 76(9), p.094113_1 - 094113_10, 2007/09

 Times Cited Count:10 Percentile:44.59(Materials Science, Multidisciplinary)

Structural relations between two ground states of the ANNNI (Axial Next Nearest Neighbor Ising) compound NaV$$_{2}$$O$$_{5}$$, C$$_{1/4}$$- and C$$_{0}$$-phases below and above the transition pressure $$P_{rm C}$$ = 1 GPa, were investigated by X-ray diffraction and scattering techniques. The structure of the C$$_{0}$$-phase is well explained by the $$A$$($$A'$$) pattern which is one of four layers ($$AAA'A'$$) of the C$$_{1/4}$$-phase, however, the amount of the atomic shifts under the conditions 1.6 GPa and 6 K is 27% that under ambient pressure. On the other hand, resonant X-ray scattering showed that the charges are disproportionated under high pressure. Based on these facts, it was concluded that charge disproportionation corresponds to the Ising variable in NaV$$_{2}$$O$$_{5}$$, where the atomic shifts are regarded as linearly coupled to the Ising spins. These results lead to the hypothesis that the competitive interactions between the Ising spins may result from the Ising spin-phonon coupling.

JAEA Reports

HTTR operation data base, 2; Examples of the HTTR core characteristics data base, etc

Nojiri, Naoki; Owada, Hiroyuki; Fujimoto, Nozomu

JAEA-Data/Code 2007-013, 93 Pages, 2007/06

JAEA-Data-Code-2007-013.pdf:5.34MB

For the future HTGR development and the management of the High Temperature engineering Test Reactor(HTTR), the HTTR operation data base is constructed. The data base consists of the sorted or evaluated data based on the measured values from the HTTR's operation, such as excess reactivity of the core, temperature at facilities of the core and the plant, impurities in coolant and so on. The data base also consists of some sub-databases which have objects related to the future HTGR development or the HTTR's operational management in order to manage the important operation data systematically on a long term. This paper describes examples of the HTTR common data base, the HTTR nuclear characteristics data base, the helium purity control data base and the other data base.

Journal Articles

High-magnetic-field X-ray absorption spectroscopy of field-induced valence transition in YbInCu$$_4$$

Matsuda, Yasuhiro*; Inami, Toshiya; Owada, Kenji; Murata, Yuto*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Ota, Hiroto*; Zhang, W.*; Yoshimura, Kazuyoshi*

Journal of the Physical Society of Japan, 76(3), p.034702_1 - 034702_6, 2007/03

 Times Cited Count:54 Percentile:86.3(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

High field X-ray diffraction study on a magnetic-field-induced valence transition in YbInCu$$_4$$

Matsuda, Yasuhiro*; Inami, Toshiya; Owada, Kenji; Murata, Yuto*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Ota, Hiroto*; Zhang, W.*; Yoshimura, Kazuyoshi*

Journal of the Physical Society of Japan, 75(2), p.024710_1 - 024710_5, 2006/02

 Times Cited Count:39 Percentile:81.42(Physics, Multidisciplinary)

We report the first high-field X-ray diffraction experiment using synchrotron X-rays and pulsedmagnetic fields exceeding 30 T. The lattice deformation due to a magnetic-field-induced valencetransition in YbInCu$$_4$$ is studied. It has been found that the Bragg reflection profile at 32K changessignificantly at around 27 T due to the structural transition. In the vicinity of the transition field, the lowfield and high field phases alternate with the discontinuous change in the lattice constant. Thus, it isevident that the field-induced valence state transition is a first-order phase transition. The fielddependence of the low-field-phase Bragg peak intensity is found to be roughly scaled with themagnetization.

Journal Articles

Quest for the high-filed phase of CdCr$$_2$$O$$_4$$ using an X-ray diffraction technique

Inami, Toshiya; Owada, Kenji; Tsubota, Masami; Murata, Yuto*; Matsuda, Yasuhiro*; Nojiri, Hiroyuki*; Ueda, Hiroaki*; Murakami, Yoichi*

Journal of Physics; Conference Series, 51, p.502 - 505, 2006/00

 Times Cited Count:16 Percentile:97.58

no abstracts in English

Journal Articles

Application of miniature pulsed magnets to synchrotron X-ray spectroscopy and neutron diffraction

Matsuda, Yasuhiro*; Murata, Yuto*; Inami, Toshiya; Owada, Kenji; Nojiri, Hiroyuki*; Oyama, Kenji*; Kato, Naoki*; Murakami, Yoichi*; Iga, Fumitoshi*; Takabatake, Toshiro*; et al.

Journal of Physics; Conference Series, 51, p.490 - 493, 2006/00

 Times Cited Count:8 Percentile:92.41

34 (Records 1-20 displayed on this page)