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Journal Articles

Microstructural stability of ODS steel after very long-term creep test

Oka, Hiroshi; Tanno, Takashi; Yano, Yasuhide; Otsuka, Satoshi; Kaito, Takeji; Tachi, Yoshiaki

Journal of Nuclear Materials, 547, p.152833_1 - 152833_7, 2021/04

 Times Cited Count:5 Percentile:72.51(Materials Science, Multidisciplinary)

In order to evaluate the stability of nano-sized oxide particles and matrix structure of ODS cladding tube, which are the determinants of their high temperature strength, the microstructural observation was carried out after internal pressurized creep test at 700$$^{circ}$$C for over 45,000 hours. The specimens were the as-received and crept specimens of 9Cr-ODS steel with tempered martensite and 12Cr-ODS steel with recrystallized ferrite. Small platelet was cut out from the crept pressurized tube, then thinned to foil. Microstructural observation was conducted with TEM JEOL 2010F. As a result of the observation, it was confirmed that the size and number density of the nano-sized particles were almost unchanged even after the creep test. In addition, the tempered martensite structure, which is one of the determinants of the creep strength of 9Cr-ODS steel, was not significantly different between the as-received and crept specimen, indicating the stability of their matrix structure.

Journal Articles

Microstructure distribution of Japanese sword cross sections analyzed by the diffractometer TAKUMI at J-PARC

Oikawa, Kenichi; Harjo, S.; Pham, A. H.*; Kawasaki, Takuro; Morito, Shigekazu*; Kiyanagi, Yoshiaki*; Shinohara, Takenao; Kai, Tetsuya; Oba, Takuya*; Ito, Masakazu*

JPS Conference Proceedings (Internet), 33, p.011062_1 - 011062_6, 2021/03

Journal Articles

Development of ODS tempered martensitic steel for high burn up fuel cladding tube of SFR

Otsuka, Satoshi; Tanno, Takashi; Oka, Hiroshi; Yano, Yasuhide; Tachi, Yoshiaki; Kaito, Takeji; Hashidate, Ryuta; Kato, Shoichi; Furukawa, Tomohiro; Ito, Chikara; et al.

2018 GIF Symposium Proceedings (Internet), p.305 - 314, 2020/05

Oxide Dispersion Strengthened (ODS) steel has been developed worldwide as a high-strength and radiation-tolerant steel used for advanced nuclear system. Japan Atomic Energy Agency (JAEA) has been developing ODS steel as the primary candidate material of Sodium cooled Fast Reactor (SFR) high burn-up fuel cladding tube. Application of high burn-up fuel to SFR core can contribute to improvement of economical performance of SFR in conjunction with volume and hazardousness reduction of radioactive waste. This paper described the current status and future prospects of ODS tempered martensitic steel development in JAEA for SFR fuel application.

Journal Articles

An Experimental setup for creating and imaging $$^{4}$$He$$_{2}$$$$^{ast}$$ excimer cluster tracers in superfluid helium-4 via neutron-$$^{3}$$He absorption reaction

Sonnenschein, V.*; Tsuji, Yoshiyuki*; Kokuryu, Shoma*; Kubo, Wataru*; Suzuki, So*; Tomita, Hideki*; Kiyanagi, Yoshiaki*; Iguchi, Tetsuo*; Matsushita, Taku*; Wada, Nobuo*; et al.

Review of Scientific Instruments, 91(3), p.033318_1 - 033318_12, 2020/03

 Times Cited Count:0 Percentile:0(Instruments & Instrumentation)

Journal Articles

Pulsed neutron imaging based crystallographic structure study of a Japanese sword made by Sukemasa in the Muromachi period

Oikawa, Kenichi; Kiyanagi, Yoshiaki*; Sato, Hirotaka*; Omae, Kazuma*; Pham, A.*; Watanabe, Kenichi*; Matsumoto, Yoshihiro*; Shinohara, Takenao; Kai, Tetsuya; Harjo, S.; et al.

Materials Research Proceedings, Vol.15, p.207 - 213, 2020/02

Journal Articles

Local structure study of the iron-based systems of BaFe$$_2$$As$$_2$$ and LiFeAs by X-ray PDF and XAFS analyses

Li, S.*; Toyoda, Masayuki*; Kobayashi, Yoshiaki*; Ito, Masayuki*; Ikeuchi, Kazuhiko*; Yoneda, Yasuhiro; Otani, Akira*; Matsumura, Daiju; Asano, Shun*; Mizuki, Junichiro*; et al.

Physica C, 555, p.45 - 53, 2018/12

 Times Cited Count:1 Percentile:5.84(Physics, Applied)

${it T}$-dependence of local distortions in BaFe$$_2$$As$$_2$$ and LiFeAs by X-ray PDF and XAFS methods. Although PDF data exhibit anomaly at the structure transition temperature, EXAFS data exhibit no anomaly. Data supporting the local orthorhombicity at 300 K in the tetragonal phase for BaFe$$_2$$As$$_2$$. Arguments on the origins of the 4-fold symmetry breaking in the ground average structure of the tetragonal phase.

Journal Articles

Study for estimation of snow depth by using DSM made by SfM method

Miyasaka, Satoshi*; Unome, Sota*; Tamura, Ayako*; Ito, Yoshiaki*; Ishizaki, Azusa; Sanada, Yukihisa

Nihon Rimoto Senshingu Gakkai Dai-63-Kai (Heisei-29-Nendo Shuki) Gakujutsu Koenkai Rombunshu (CD-ROM), p.81 - 84, 2017/11

Information of snow depth is important to improve the airborne radiation measurement in the winter. The snow depth is enable to estimate by the aerial photograph which is obtained at the same time with the radiation measurement before and after the snowfall. We attempted optimization parameters which used to make a Digital Surface Model (DSM) using Structure from Motion (SfM) method for estimation of the snow depth. As a result, to enable to measure precisely the snow depth was indicated. However, the estimated snow depth in the forest area was relatively not so accurate because fallen leaves and a tree move were prevented to measure DSM precisely.

Journal Articles

$$gamma$$ decay of unbound neutron-hole states in $$^{133}$$Sn

Vaquero, V.*; Jungclaus, A.*; Doornenbal, P.*; Wimmer, K.*; Gargano, A.*; Tostevin, J. A.*; Chen, S.*; N$'a$cher, E.*; Sahin, E.*; Shiga, Yoshiaki*; et al.

Physical Review Letters, 118(20), p.202502_1 - 202502_5, 2017/05

 Times Cited Count:18 Percentile:76.22(Physics, Multidisciplinary)

Journal Articles

Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd$$_{3}$$(Al,Ga)$$_{5}$$O$$_{12}$$ scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.

Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12

 Times Cited Count:31 Percentile:95.74(Nuclear Science & Technology)

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 4$$times$$4 to 8$$times$$8 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m $$times$$ 60 m and 65 m $$times$$ 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the $$gamma$$-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10$$^{circ}$$).

Journal Articles

Phonons of Fe-based superconductor Ca$$_{10}$$Pt$$_4$$As$$_8$$(Fe$$_{1-x}$$Pt$$_x$$As)$$_{10}$$

Ikeuchi, Kazuhiko*; Kobayashi, Yoshiaki*; Suzukia, Kazunori*; Ito, Masayuki*; Kajimoto, Ryoichi; Bourges, P.*; Christianson, A. D.*; Nakamura, Hiroki; Machida, Masahiko; Sato, Masatoshi*

Journal of Physics; Condensed Matter, 27(46), p.465701_1 - 465701_7, 2015/11

 Times Cited Count:1 Percentile:5.05(Physics, Condensed Matter)

We report the results of inelastic neutron scattering measurements on particular phonons of a superconducting (SC) Ca$$_{10}$$Pt$$_4$$As$$_8$$(Fe$$_{1-x}$$Pt$$_x$$As)$$_{10}$$ with the onset transition temperature $$T_c sim 33$$ K to investigate mainly what roles orbital fluctuation plays in Cooper pairing, where we observed a slight softening of the in-plane transverse acoustic mode corresponding to the elastic constant $$C_{66}$$. This softening starts at temperature $$T$$ well above the SC $$T_c$$, as $$T$$ decreases. An anomalously strong change of the scattering intensity of in-plane optical modes was observed at the M point of the pseudo tetragonal reciprocal space in the range of 35 $$< omega <$$ 40 meV with decreasing $$T$$ from far above $$T_c$$. Because this $$omega$$ region mainly corresponds to the motion of Fe and As atoms in the FeAs planes, the finding presents information on the coupling between the orbital fluctuation of Fe $$3d$$ electrons and the lattice system, useful for studying the possible roles of orbital fluctuation in the pairing mechanism and/or the appearance of the so-called nematic phase.

Journal Articles

Current post irradiation examination techniques at the JMTR Hot laboratory

Shibata, Akira; Kato, Yoshiaki; Oishi, Makoto; Taguchi, Taketoshi; Ito, Masayasu; Yonekawa, Minoru; Kawamata, Kazuo

KAERI/GP-418/2015, p.151 - 165, 2015/05

The JMTR stopped its operation in 2006 for refurbishment. The reactor facilities have been refurbished from 2007. After refurbishment, JMTR Hot laboratory is expected to perform various post irradiation examinations. In this report, installations of experimental apparatuses and recent experimental method are introduced. (1) A nano-indenter with radius spherical indenter. Inverse analysis using FEM could presume material constants from load-depth curve of indentation. Mechanical properties of oxide layer of zirconium alloy and irradiated stainless steel will be analyzed. (2) Transmission Electron Microscope (TEM). TEM is capable of imaging at a significantly higher resolution than light microscopes or normal SEM. JAEA installed a TEM apparatus (JEOL JEM-2800) in JMTR Hot laboratory. The maximum magnification is 150,000,000 times. It can be operated from a remote location using a computer network. This contributes to the convenience of remote researchers and reducing the amount of exposure.

Journal Articles

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; Koga, J. K.; Mori, Michiaki; Kawase, Keigo*; et al.

RAL-TR-2015-025, P. 22, 2015/00

Journal Articles

Study on surface tension modeling for mechanistic evaluation of vortex cavitation

Ito, Kei; Ezure, Toshiki; Ohshima, Hiroyuki; Kawamura, Takumi*; Nakamine, Yoshiaki*

Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 6 Pages, 2014/11

The authors have been studied the vortex cavitation in sodium-cooled fast reactors. In this paper, the authors present a modified evaluation method for vortex cavitation, in which a surface tension is modeled mechanistically. Namely, the cavity radius is calculated in consideration of radial pressure distribution, saturated vapor pressure and the pressure jump condition at an interface. As the basic validation of the developed surface tension model, numerical analyses of a simple experiment under various velocity conditions are performed. The evaluation results give qualitatively appropriate tendency, that is, the cavity radius becomes larger with the higher liquid velocity and/or lower reference pressure which cause the larger pressure drop at the vortex. In addition, the authors evaluate the influence of the kinematic viscosity which plays an important role in the vortex cavitation occurrences in the experiments.

Journal Articles

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; et al.

New Journal of Physics (Internet), 16(9), p.093003_1 - 093003_30, 2014/09

 Times Cited Count:30 Percentile:82.1(Physics, Multidisciplinary)

Journal Articles

Electronic structure of BaTiO$$_{3}$$ using resonant X-ray emission spectroscopy at the Ba-L$$_{3}$$ and Ti K absorption edges

Yoshii, Kenji; Yoneda, Yasuhiro; Jarrige, I.*; Fukuda, Tatsuo; Nishihata, Yasuo; Suzuki, Chikashi; Ito, Yoshiaki*; Terashima, Takahito*; Yoshikado, Shinzo*; Fukushima, Sei*

Journal of Physics and Chemistry of Solids, 75(3), p.339 - 343, 2014/03

 Times Cited Count:9 Percentile:40.44(Chemistry, Multidisciplinary)

We have studied the electronic properties of ferroelectric BaTiO$$_{3}$$ using two complementary bulk-sensitive spectroscopic probes, resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS). Contrary to a previous study, we found no temperature change of a PFY-XAS spectrum at the Ba L$$_{3}$$ edge between room temperature and 150$$^{circ}$$C. This result is not supportive of the possible presence of the displacement around Ba$$^{2+}$$ at the Curie temperature. RXES spectra were measured at the Ti K edge for BaTiO$$_{3}$$, along with SrTiO$$_{3}$$ and La-doped metallic SrTiO$$_{3}$$. The photon energy of the emission peak is found to be nearly constant throughout the absorption edge for all three compounds. We deduce the Ti 3d states to have a delocalized character, in contrast with the Ba 5d states, a property which is consistent with the proposed scenario of the formation of electric dipoles in BaTiO$$_{3}$$.

JAEA Reports

Study on evaluation method for gas entrainment and vortex cavitation phenomena; Evaluation of gas entrainment behavior in large-scale test and development of proto-type evaluation method for vortex cavitation

Ito, Kei; Ezure, Toshiki; Ohno, Shuji; Kamide, Hideki; Nakamine, Yoshiaki*; Imai, Yasutomo*

JAEA-Research 2013-007, 75 Pages, 2013/10

JAEA-Research-2013-007.pdf:5.21MB

In Japan Atomic Energy Agency (JAEA), various thermal hydraulics phenomena in an upper plenum region are evaluated in the study on the safety design criteria of the sodium-cooled fast reactor in Japan (JSFR). The gas entrainment (GE) from a free surface of coolant and the vortex cavitation (VC) at the H/L intake are important phenomena to be evaluated. Since these phenomena occur by the significant pressure drop in the vicinity of a vortex center, a technique to evaluate a vortex behavior is indispensable. The authors are developing a GE evaluation method using a numerical analysis and a vortex model. In this study, the evaluations are performed on the GE behavior in the 1/1.8 scaled water model test. In addition, a VC evaluation method is proposed on the basis of the GE evaluation method. As a basic validation of the VC evaluation method, the basic sub-surface vortex test in JAEA is evaluated.

JAEA Reports

Conceptual design of multipurpose compact research reactor; Annual report FY2011

Watahiki, Shunsuke; Hanakawa, Hiroki; Imaizumi, Tomomi; Nagata, Hiroshi; Ide, Hiroshi; Komukai, Bunsaku; Kimura, Nobuaki; Miyauchi, Masaru; Ito, Masayasu; Nishikata, Kaori; et al.

JAEA-Technology 2013-021, 43 Pages, 2013/07

JAEA-Technology-2013-021.pdf:5.12MB

The number of research reactors in the world is decreasing because of their aging. On the other hand, the necessity of research reactor, which is used for human resources development, progress of the science and technology, industrial use and safety research is increasing for the countries which are planning to introduce the nuclear power plants. From above background, the Neutron Irradiation and Testing Reactor Center began to discuss a basic concept of Multipurpose Compact Research Reactor (MCRR) for education and training, etc., on 2010 to 2012. This activity is also expected to contribute to design tool improvement and human resource development in the center. In 2011, design study of reactor core, irradiation facilities with high versatility and practicality, and hot laboratory equipment for the production of Mo-99 was carried out. As the result of design study of reactor core, subcriticality and operation time of the reactor in consideration of an irradiation capsule, and about the transient response of the reactor to the reactivity disturbance during automatic control operation, it was possible to do automatic operation of MCRR, was confirmed. As the result of design study of irradiation facilities, it was confirmed that the implementation of an efficient mass production radioisotope Mo-99 can be expected. As the result of design study with hot laboratory facilities, Mo-99 production, RI export devised considered cell and facilities for exporting the specimens quickly was designed.

Journal Articles

Probing the Ba 5d states in BaTiO$$_{3}$$ and BaSO$$_{4}$$; A Resonant X-ray emission study at the Ba-L$$_{3}$$ edge

Yoshii, Kenji; Jarrige, I.; Suzuki, Chikashi; Matsumura, Daiju; Nishihata, Yasuo; Yoneda, Yasuhiro; Fukuda, Tatsuo; Tamura, Kazuhisa; Ito, Yoshiaki*; Mukoyama, Takeshi*; et al.

Journal of Physics and Chemistry of Solids, 73(9), p.1106 - 1110, 2012/09

 Times Cited Count:11 Percentile:45.32(Chemistry, Multidisciplinary)

We have directly probed the Ba 5d states in the ferroelectric barium titanate BaTiO$$_{3}$$ using resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L$$_{3}$$ edge. The results are compared with those of the non-ferroelectric BaSO$$_{4}$$. While the RXES spectra point to a localized character for the Ba 5d states in both compounds, the main peak of the PFY-XAS spectrum, corresponding to the dipolar transitions from 2p to 5d, is found to be significantly broader for BaTiO$$_{3}$$ than for BaSO$$_{4}$$. On the basis of band structure calculations, this broadening is ascribed to strong hybridization between the unoccupied Ba 5d and O 2p states in the ferroelectric. This suggests that the hybridization between the conduction states of the Ba$$^{2+}$$ and O$$^{2-}$$ ions, and not only Ti$$^{4+}$$ and O$$^{2-}$$, plays a central role in determining the electronic structure of BaTiO$$_{4}$$.

Journal Articles

Relativistic high harmonic generation in gas jet targets

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

AIP Conference Proceedings 1465, p.167 - 171, 2012/07

 Times Cited Count:1 Percentile:47.22

Journal Articles

High-order harmonics from bow wave caustics driven by a high-intensity laser

Esirkepov, T. Z.; Pirozhkov, A. S.; Kando, Masaki; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

AIP Conference Proceedings 1465, p.172 - 180, 2012/07

 Times Cited Count:0 Percentile:0.13

The bow wave induced mechanism of high-order harmonics generation was discovered using simulations and catastrophe theory. This mechanism feasibility was successfully demonstrated in 3D and 2D PIC simulations. The mechanism and the simulations explained high-order harmonics in the XUV spectral region seen in recent experiments with terawatt lasers. Development of new XUV light and X-ray source based on the high-order harmonics generation mechanism is proposed.

116 (Records 1-20 displayed on this page)