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Journal Articles

Crack expansion and fracturing mode of hydraulic refracturing from Acoustic Emission monitoring in a small-scale field experiment

Ishida, Tsuyoshi*; Fujito, Wataru*; Yamashita, Hiroto*; Naoi, Makoto*; Fujii, Hirokazu*; Suzuki, Kenichiro*; Matsui, Hiroya

Rock Mechanics and Rock Engineering, 52(2), p.543 - 553, 2019/02

 Times Cited Count:1 Percentile:37.88(Engineering, Geological)

We pressurized and injected water in a hole drilled downward from a floor of the 500 m level gallery in MIU, central Japan. Acoustic emissions (AEs) monitored with 16 sensors in four boreholes located 1 m away from the HF hole exhibited two-dimensional distributions, which likely delineate a crack induced by the fracturing. Expansions of the regions in which AEs occurred were observed only immediately after the first and second BDs. Many AE events in other periods were distributed within the regions where AE events had already occurred. The initial motion polarities of P-waves indicate that tensile-dominant AE events occurred when the regions expanded and they were distributed primarily on the frontiers of the regions where AE events had already occurred. The experimental results suggest that increasing the injection flow rate is effective for generating new cracks in the refracturing, with the new crack expansions being induced by tensile fracturing.

Journal Articles

Analysis of transport behaviors of cesium and iodine in VERDON-2 experiment for chemical model validation

Shiotsu, Hiroyuki; Ito, Hiroto*; Ishikawa, Jun; Sugiyama, Tomoyuki; Maruyama, Yu

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 6 Pages, 2018/11

JAEA Reports

CHEMKEq; Evaluation code for chemical composition based on partial mixed model with Chemical Equilibrium and Reaction Kinetics (Contract research)

Ito, Hiroto*; Shiotsu, Hiroyuki; Tanaka, Yoichi*; Nishihara, Satomichi*; Sugiyama, Tomoyuki; Maruyama, Yu

JAEA-Data/Code 2018-012, 42 Pages, 2018/10

JAEA-Data-Code-2018-012.pdf:4.93MB

Chemical composition of fission products transported in nuclear facilities in severe accidents is controlled by slower chemical reaction rates, therefore, it could be different from that evaluated on the chemical equilibrium assumption. Hence, it is necessary to evaluate the chemical composition with reaction kinetics. On the other hand, databases applicable to the analysis of nuclear facilities have not been constructed because knowledge of reaction rates of complex chemical reactions in severe accidents is currently limited. Accordingly, we have developed the CHEMKEq code based on a partial mixed model with chemical equilibrium and reaction kinetics to decrease uncertainties of the chemical composition caused by the reaction rate. The CHEMKEq code, under mass conservation law, firstly evaluates chemical species obeying the chemical equilibrium model, and then, relatively slow reactions are solved by the reaction kinetics model. Moreover, the CHEMKEq code has a multiplicity of use in evaluations of chemical composition because general chemical equilibrium and reaction kinetics models are also available and databases required to calculation are external file formats. This report is the user's guide of the CHEMKEq code, showing models, solution methods, structure of the code and calculation examples. And information to run the CHEMKEq code is summarized in appendixes.

Journal Articles

Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex, 3; Neutron devices and computational and sample environments

Sakasai, Kaoru; Sato, Setsuo*; Seya, Tomohiro*; Nakamura, Tatsuya; To, Kentaro; Yamagishi, Hideshi*; Soyama, Kazuhiko; Yamazaki, Dai; Maruyama, Ryuji; Oku, Takayuki; et al.

Quantum Beam Science (Internet), 1(2), p.10_1 - 10_35, 2017/09

Neutron devices such as neutron detectors, optical devices including supermirror devices and $$^{3}$$He neutron spin filters, and choppers are successfully developed and installed at the Materials Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), Tokai, Japan. Four software components of MLF computational environment, instrument control, data acquisition, data analysis, and a database, have been developed and equipped at MLF. MLF also provides a wide variety of sample environment options including high and low temperatures, high magnetic fields, and high pressures. This paper describes the current status of neutron devices, computational and sample environments at MLF.

Journal Articles

Experimental observation of temperature and magnetic-field evolution of the 4${it f}$ states in CeFe$$_{2}$$ revealed by soft X-ray magnetic circular dichroism

Saito, Yuji; Yasui, Akira*; Fuchimoto, Hiroto*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Imada, Shin*; Narumi, Yasuo*; Kindo, Koichi*; Takahashi, Minoru*; Ebihara, Takao*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

We revisit the delocalized character of the 4$$f$$ states of CeFe$$_2$$ in the ferromagnetically ordered phase by X-ray magnetic circular dichroism (XMCD) in X-ray absorption spectroscopy (XAS) with improved data quality using single crystals. Surprisingly, the Ce $$M_{4,5}$$ XMCD spectral shape changes significantly as a function of temperature and applied magnetic field, with no concomitant changes in the spectral shape of the Ce $$M_{4,5}$$ XAS as well as the Fe $$L_{2,3}$$ XAS and XMCD. This unusual behavior is characterized by the $$J=7/2$$ states in a 4$$f^1$$ configuration mixed into the $$J=5/2$$ ground state. Such extreme sensitivity of the Ce 4$$f$$ states to the external perturbations can be related to the magnetic instability toward an antiferromagnetic phase in CeFe$$_2$$. Our experimental data presented here provide valuable insights into the underlying physics in strongly-hybridized ferromagnetic Ce compounds.

Journal Articles

2016 Professional Engineer (PE) test preparation course; Nuclear and radiation technical disciplines

Takahashi, Naoki; Suzuki, Soju; Saito, Hiroto; Ueno, Takashi; Abe, Sadayoshi; Yamanaka, Atsushi; Tanigawa, Masafumi; Nakamura, Daishi; Sasaki, Shunichi; Mine, Tadaharu

Nippon Genshiryoku Gakkai Homu Peji (Internet), 20 Pages, 2017/05

no abstracts in English

Journal Articles

Fine dispersion of Pt$$_{4-5}$$ subnanoclusters and Pt single atoms over porous carbon supports and their structural analyses with X-ray absorption spectroscopy

Itoi, Hiroyuki*; Nishihara, Hirotomo*; Kobayashi, Shunsuke*; Ittisanronnachai, S.*; Ishii, Takafumi*; Berenguer, R.*; Ito, Masashi*; Matsumura, Daiju; Kyotani, Takashi*

Journal of Physical Chemistry C, 121(14), p.7892 - 7902, 2017/04

 Times Cited Count:16 Percentile:19.32(Chemistry, Physical)

Journal Articles

Electronic structures of ferromagnetic CeAgSb$$_{2}$$; Soft X-ray absorption, magnetic circular dichroism, and angle-resolved photoemission spectroscopies

Saito, Yuji; Fujiwara, Hidenori*; Yamaguchi, Takashi*; Nakatani, Yasuhiro*; Mori, Takeo*; Fuchimoto, Hiroto*; Kiss, Takayuki*; Yasui, Akira*; Miyawaki, Jun*; Imada, Shin*; et al.

Journal of the Physical Society of Japan, 85(11), p.114713_1 - 114713_7, 2016/11

 Times Cited Count:7 Percentile:35.05(Physics, Multidisciplinary)

We report on the electronic structures of ferromagnetic CeAgSb$$_{2}$$ using soft X-ray absorption (XAS), magnetic circular dichroism (XMCD), and angle-resolved photoemission (ARPES) spectroscopies. The Ce $$M_{4,5}$$ XAS spectra show very small satellite structures, reflecting a strongly localized character of the Ce 4${it f}$ electrons. The linear dichroism effects in the Ce $$M_{4,5}$$ XAS spectra demonstrate the ground-state Ce 4${it f}$ symmetry of $$Gamma$$$$_{6}$$, the spatial distribution of which is directed along the ${it c}$-axis. Nevertheless, ARPES spectra at the Ce 3$$d$$-4$$f$$ resonance show the momentum dependence of the intensity ratio between Ce 4$$f^{1}_{5/2}$$ and 4$$f^{1}_{7/2}$$ peaks in a part of the Brillouin zone, suggesting the non negligible momentum-dependent hybridization effect between the Ce 4${it f}$ and the conduction electrons. This is associated with the moderate mass enhancement in CeAgSb$$_{2}$$.

Journal Articles

Statistical analysis using the Bayesian nonparametric method for irradiation embrittlement of reactor pressure vessels

Takamizawa, Hisashi; Ito, Hiroto; Nishiyama, Yutaka

Journal of Nuclear Materials, 479, p.533 - 541, 2016/10

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

To understand neutron irradiation embrittlement in high fluence regions, statistical analysis using the Bayesian nonparametric (BNP) method was performed for the Japanese surveillance and material test reactor irradiation database. The BNP method is essentially expressed as an infinite summation of normal distributions, with input data being subdivided into clusters with identical statistical parameters (such as mean and standard deviation) for each cluster to estimate shifts in ductile-to-brittle transition temperature (DBTT). Clusters typically depend on chemical compositions, irradiation conditions, and the irradiation embrittlement. Specific variables contributing to the irradiation embrittlement include the content of Cu, Ni, P, Si, and Mn in the pressure vessel, neutron flux, neutron fluence, and irradiation temperatures. It was found through numerous examinations that the measured shifts of DBTT correlated well with calculated ones. Data associated with the same materials were subdivided into the same clusters even if neutron fluences were significantly disparate among the results. This indicates that slowly developing or late-onset embrittlement mechanisms were not evident in the present study.

Journal Articles

Thermoelectric generation based on spin Seebeck effects

Uchida, Kenichi*; Adachi, Hiroto; Kikkawa, Takashi*; Kirihara, Akihiro*; Ishida, Masahiko*; Yorozu, Shinichi*; Maekawa, Sadamichi; Saito, Eiji*

Proceedings of the IEEE, 104(10), p.1946 - 1973, 2016/10

 Times Cited Count:100 Percentile:0.57(Engineering, Electrical & Electronic)

Journal Articles

An Integrated approach to source term uncertainty and sensitivity analysis for nuclear reactor severe accidents

Zheng, X.; Ito, Hiroto; Tamaki, Hitoshi; Maruyama, Yu

Journal of Nuclear Science and Technology, 53(3), p.333 - 344, 2016/03

AA2014-0796.pdf:0.84MB

 Times Cited Count:4 Percentile:40.16(Nuclear Science & Technology)

Journal Articles

Origin of the spin Seebeck effect in compensated ferrimagnets

Gepr$"a$gs, S.*; Kehlberger, A.*; Coletta, F.*; Qiu, Z.*; Guo, E.-J.*; Schulz, T.*; Mix, C.*; Meyer, S.*; Kamra, A.*; Althammer, M.*; et al.

Nature Communications (Internet), 7, p.10452_1 - 10452_6, 2016/02

 Times Cited Count:70 Percentile:2.76(Multidisciplinary Sciences)

Journal Articles

2016 Professional Engineer (PE) test preparation course "Nuclear and Radiation Technical Disciplines"

Takahashi, Naoki; Yoshinaka, Kazuyuki; Harada, Akio; Yamanaka, Atsushi; Ueno, Takashi; Kurihara, Ryoichi; Suzuki, Soju; Takamatsu, Misao; Maeda, Shigetaka; Iseki, Atsushi; et al.

Nippon Genshiryoku Gakkai Homu Peji (Internet), 64 Pages, 2016/00

no abstracts in English

Journal Articles

Unconventional scaling and significant enhancement of the spin Seebeck effect in multilayers

Ramos, R.*; Kikkawa, Takashi*; Aguirre, M.*; Lucas, I.*; Anad$'o$n, A.*; Oyake, Takafumi*; Uchida, Kenichi*; Adachi, Hiroto; Shiomi, Junichiro*; Algarabel, P. A.*; et al.

Physical Review B, 92(22), p.220407_1 - 220407_5, 2015/12

 Times Cited Count:43 Percentile:7.69(Materials Science, Multidisciplinary)

Journal Articles

Magnon instability driven by heat current in magnetic bilayers

Onuma, Yuichi*; Adachi, Hiroto; Saito, Eiji; Maekawa, Sadamichi

Physical Review B, 92(22), p.224404_1 - 224404_8, 2015/12

 Times Cited Count:6 Percentile:59(Materials Science, Multidisciplinary)

Journal Articles

Source term uncertainty analysis; Probabilistic approaches and applications to a BWR severe accident

Zheng, X.; Ito, Hiroto; Tamaki, Hitoshi; Maruyama, Yu

Mechanical Engineering Journal (Internet), 2(5), p.15-00032_1 - 15-00032_14, 2015/10

Journal Articles

Superdeformation in $$^{35}$$S

Go, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Kobayashi, Motoki*; Kisamori, Keiichi*; Takaki, Motonobu*; Miya, Hiroyuki*; Ota, Shinsuke*; Michimasa, Shinichiro*; Shimoura, Susumu*; et al.

JPS Conference Proceedings (Internet), 6, p.030005_1 - 030005_4, 2015/06

Journal Articles

Application of Bayesian nonparametric models to the uncertainty and sensitivity analysis of source term in a BWR severe accident

Zheng, X.; Ito, Hiroto; Kawaguchi, Kenji; Tamaki, Hitoshi; Maruyama, Yu

Reliability Engineering & System Safety, 138, p.253 - 262, 2015/06

 Times Cited Count:3 Percentile:71.18(Engineering, Industrial)

Journal Articles

Influence of adsorption of molecular iodine onto aerosols on iodine source term in severe accident

Ishikawa, Jun; Ito, Hiroto; Maruyama, Yu

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

Journal Articles

Generation of spin currents by surface plasmon resonance

Uchida, Kenichi*; Adachi, Hiroto; Kikuchi, Daisuke*; Ito, Shun*; Qiu, Z.*; Maekawa, Sadamichi; Saito, Eiji

Nature Communications (Internet), 6, p.5910_1 - 5910_8, 2015/01

 Times Cited Count:28 Percentile:14.6(Multidisciplinary Sciences)

96 (Records 1-20 displayed on this page)