Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 64

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Molecular dynamic simulations evaluating the effect of the stacking fault energy on defect formations in face-centered cubic metals subjected to high-energy particle irradiation

Terayama, Satoshi*; Iwase, Yuki*; Hayakawa, Sho*; Okita, Taira*; Itakura, Mitsuhiro; Suzuki, Katsuyuki*

Computational Materials Science, 195, p.110479_1 - 110479_12, 2021/07

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

Journal Articles

Isomer production ratio of the $$^{112}$$Cd($$n,gamma$$)$$^{113}$$Cd reaction in an $$s$$-process branching point

Hayakawa, Takehito*; Toh, Yosuke; Kimura, Atsushi; Nakamura, Shoji; Shizuma, Toshiyuki*; Iwamoto, Nobuyuki; Chiba, Satoshi*; Kajino, Toshitaka*

Physical Review C, 103(4), p.045801_1 - 045801_5, 2021/04

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:140 Percentile:99.81(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Measurement of the isomer production ratio for the $$^{112}$$Cd($$n,gamma$$)$$^{113}$$Cd reaction using neutron beams at J-PARC

Hayakawa, Takehito*; Toh, Yosuke; Huang, M.; Shizuma, Toshiyuki*; Kimura, Atsushi; Nakamura, Shoji; Harada, Hideo; Iwamoto, Nobuyuki; Chiba, Satoshi*; Kajino, Toshitaka*

Physical Review C, 94(5), p.055803_1 - 055803_6, 2016/11

 Times Cited Count:3 Percentile:32.77(Physics, Nuclear)

Journal Articles

Neutron angular distribution in ($$gamma$$, n) reactions with linearly polarized $$gamma$$-ray beam generated by laser Compton scattering

Horikawa, Ken*; Miyamoto, Shuji*; Mochizuki, Takayasu*; Amano, So*; Li, D.*; Imasaki, Kazuo*; Izawa, Yasukazu*; Ogata, Kazuyuki*; Chiba, Satoshi*; Hayakawa, Takehito

Physics Letters B, 737, p.109 - 113, 2014/10

 Times Cited Count:11 Percentile:65.49(Astronomy & Astrophysics)

It was predicted in 1950's, the neutron angular distribution in ($$gamma$$, n) reactions with a 100% linearly polarized $$gamma$$-ray beam should be anisotropic and described by a simple function of a + b sin$$^{2}$$$${theta}$$ at 90$$^{circ}$$ on the beam axis but it has not been experimentally confirmed for middle-heavy nuclides over than half a century. We have verified experimentally this angular distribution on $$^{197}$$Au, $$^{127}$$I, and natural Cu using linearly polarized laser Compton scattering $$gamma$$-rays at NewSUBARU.

Journal Articles

Supernova neutrino nucleosynthesis of the radioactive $$^{92}$$Nb observed in primitive meteorites

Hayakawa, Takehito; Nakamura, Ko*; Kajino, Toshitaka*; Chiba, Satoshi; Iwamoto, Nobuyuki; Cheoun, M. K.*; Mathews, G. J.*

Astrophysical Journal Letters, 779(1), p.L9_1 - L9_5, 2013/12

 Times Cited Count:24 Percentile:62.68(Astronomy & Astrophysics)

Short-lived radioactivities are used as nuclearcosmochronometers for understanding the free decay time from the last nucleosynthesis episode until the time of solar system formation (SSF). $$^{92}$$Nb (half-life of 34.7 Myr) is one of a short-lived isotope existed at SSF. However, there is a controversy in that the inferred initial abundance ratios for $$^{92}$$Nb/$$^{93}$$Nb at the time of SSF cluster around two different values; one is near 10$$^{-3}$$, while the other is near 10$$^{-5}$$. Moreover, the astrophysical mechanism for the synthesis of $$^{92}$$Nb has remained an unsolved problem. Here we argue that conventional nucleosynthesis mechanisms cannot produce $$^{92}$$Nb and propose a new mechanism for the nucleosynthesis of this isotopebased upon neutrino induced reactions occurring during core-collapse supernova explosions.

Journal Articles

Three-dimensional tsunami analysis for the plot plan of a sodium-cooled fast reactor plant

Hayakawa, Satoshi*; Watanabe, Osamu*; Ito, Kei; Yamamoto, Tomohiko

Nihon Kikai Gakkai Rombunshu, B, 79(808), p.2645 - 2649, 2013/12

As the practical evaluation method of the effect of tsunami on buildings, the formula of tsunami force has been used. However, it cannot be applied to complex geometry of buildings. In this study, to analyze the effect of tsunami on the buildings of sodium-cooled fast reactor plant more accurately, three-dimensional tsunami analysis was performed. In the analysis, VOF (Volume of Fluid) method was used to capture free surface of tsunami. At the beginning, it was confirmed that the tsunami experiment results was reproduced by VOF method accurately. Next, the three-dimensional tsunami analysis was performed with VOF method to evaluate the flow field around the buildings of the plant from the beginning of the tsunami until the backwash of that.

Journal Articles

Development of basic NDA technologies of nuclear material accountancy of debris of melted fuel formed in severe accidents

Seya, Michio; Harada, Hideo; Kitatani, Fumito; Koizumi, Mitsuo; Tsuchiya, Harufumi; Iimura, Hideki; Kureta, Masatoshi; Takamine, Jun; Hajima, Ryoichi; Hayakawa, Takehito; et al.

Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-34-Kai Nenji Taikai Rombunshu (Internet), 10 Pages, 2013/10

The forming of MF in severe accidents of nuclear reactors such as Units 1 - 3 of Fukushima-Daiichi NPP (Nuclear Power Plant) inevitably change the category of the nuclear reactor from "item facility" to "bulk-handling facility". At removal of the MF it is necessary to break chunks of MF into relatively small blocks by using some tools, resulting in debris that consists of cut or small rock-like debris and particle (or grain)-like debris in bulk form. This paper presents a categorization of debris of MF and two possible non-destructive assay (NDA) technologies for precise measurement which could be applied to the NM accountancy of MF debris. One of them is Neutron Resonance Densitometry (NRD) for particle-like (or grain-like) debris, and another is NRF (Nuclear Resonance Fluorescence) NDA using LCS (Laser Compton Scattered) $$gamma$$-rays (mono-energetic $$gamma$$-rays) for cut or small rock-like debris. The paper also describes about the recent development of these two technologies.

Journal Articles

Development of basic NDA technologies for nuclear material accountancy of debris of melted fuel formed in severe accidents

Seya, Michio; Harada, Hideo; Kitatani, Fumito; Koizumi, Mitsuo; Tsuchiya, Harufumi; Iimura, Hideki; Kureta, Masatoshi; Takamine, Jun; Hajima, Ryoichi; Hayakawa, Takehito; et al.

Proceedings of INMM 54th Annual Meeting (CD-ROM), 9 Pages, 2013/07

The forming of MF in a severe accident of a nuclear reactor may change the category of the nuclear reactor from item facility to non-item facility. Taking this removal process into account, the damaged reactor could be categorized as a bulk-handling facility. The NM accountancy is essential for the safeguards of a bulk-handling facility. This paper presents a categorization of debris of MF (into cut or small rock-like debris and particle (or grain)-like debris) and a selection of possible NDA technologies which could be applied to the NM accountancy of MF debris. The paper introduces two NDA technologies for NM accountancy of debris: NRD for particle-like (or grain-like) debris, and NRF NDA using LCS $$gamma$$ rays for cut or small rock-like debris. The paper also describes about the development of basic parts of these two technologies and near future plan.

Journal Articles

Development of flow-induced vibration evaluation methodology based on unsteady fluid flow analysis for large diameter pipe with elbow in JSFR

Hayakawa, Satoshi*; Ishikura, Shuichi*; Watanabe, Osamu*; Kaneko, Tetsuya*; Yamano, Hidemasa; Tanaka, Masaaki

Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 10 Pages, 2012/12

The present methodology was applied to the analysis for the 1/3-scale experiment of the hot-leg pipe of JSFR, and the predicted stress values were compared with the measured stress values. The predicted stress values were underestimated in the case of using the intact pressure fluctuations obtained by the unsteady fluid flow analysis. Therefore, the improvement of the prediction accuracy of the pressure fluctuations on the pipe wall was attempted.

Journal Articles

Feasibility studies and development of NDA technologies for nuclear materials in the melted fuels formed in severe accidents

Seya, Michio; Harada, Hideo; Kitatani, Fumito; Koizumi, Mitsuo; Tsuchiya, Harufumi; Iimura, Hideki; Kureta, Masatoshi; Takamine, Jun; Hajima, Ryoichi; Hayakawa, Takehito; et al.

Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-33-Kai Nenji Taikai Rombunshu (Internet), 10 Pages, 2012/10

This paper presents feasibility (selection) study of NDA techniques, NRD (Neutron Resonance Densitometry) and LCSG-NRF (LCS $$gamma$$-rays interrogation Nuclear Resonance Fluorescence), to measure nuclear material (NM) in debris of melted fuel with high precision. The melted fuel under consideration here is the one formed by the severe loss of coolant accidents of such as Units 1 - 3 of Fukushima-Daiichi NPP. NRD based on NRTA (Neutron Resonance Transmission Analysis) and NRCA (Neutron Resonance Capture Analysis) utilizing the TOF (Time of Flight) method is intended for measurement of NM (all isotopes of U/Pu) in particle-like debris. LCSG-NRF using intense LCS (Laser Compton Scattered) $$gamma$$-rays (mono-energetic $$gamma$$-rays) is to measure NM (all isotopes of U/Pu) in small rock-like debris and cut-shape debris (cylindrical, slab-shpape). In this paper we also summarize advantages of two techniques compared with other NDA techniques.

Journal Articles

Effect of swirl inflow on flow pattern and pressure fluctuation onto a single-elbow pipe in Japan Sodium-cooled Fast Reactor

Yamano, Hidemasa; Sago, Hiromi*; Hirota, Kazuo*; Hayakawa, Satoshi*; Xu, Y.*; Tanaka, Masaaki; Sakai, Takaaki

Journal of Fluid Science and Technology (Internet), 7(3), p.329 - 344, 2012/09

As part of the development of a flow-induced vibration evaluation methodology for the primary cooling piping in Japan Sodium-cooled Fast Reactor, important factors were discussed in evaluating the flow-induced vibration for the hot-leg piping. To investigate a complex flow near the inlet of the hot-leg piping, a reactor scale numerical analysis was carried out for the reactor upper plenum flow, which was simulated in a 1/10-scale reactor upper plenum experiment. Based on this analysis, experimental conditions on swirl inflow and deflected inflow that were identified as important factors were determined for flow-induced vibration experiments simulating only the hot-leg piping. In this study, the effect of the swirl inflow on flow pattern and pressure fluctuation onto the pipe wall was investigated in a 1/3-scale hot-leg pipe experiment. The experiment has indicated less significant for the pressure fluctuations, while the flow separation region was slightly influenced by the swirl flow. Computational fluid dynamics simulation results also appear in this paper, focusing on its applicability to the hot-leg piping experiments.

Journal Articles

Prediction of unsteady flow field in a primary circuit hot-leg piping of a sodium-cooled fast reactor

Tanaka, Masaaki; Sago, Hiromi*; Iwamoto, Yukiharu*; Ebara, Shinji*; Ono, Ayako; Murakami, Takahiro*; Hayakawa, Satoshi*

Nihon Kikai Gakkai Rombunshu, B, 78(792), p.1392 - 1396, 2012/08

A study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius ("short-elbow") has been conducted. Flow-induced vibration in the short-elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this paper, unsteady flow characteristics in the JSFR short-elbow pipe related to the large-scale eddy motion were estimated based on knowledge from existing studies for curved pipes and scaled water experiments and numerical simulations for the JSFR hot-leg piping.

Journal Articles

Complementary characterization of radioactivity produced by repetitive laser-driven proton beam using shot-to-shot proton spectral measurement and direct activation measurement

Ogura, Koichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Yogo, Akifumi; Nishiuchi, Mamiko; Orimo, Satoshi; Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.

Japanese Journal of Applied Physics, 51(4), p.048003_1 - 048003_2, 2012/04

 Times Cited Count:2 Percentile:10.01(Physics, Applied)

A proton beam driven by a repetitive high-intensity-laser is utilized to induce a $$^{7}$$Li(p,n)$$^{7}$$Be nuclear reaction. The total activity of $$^{7}$$Be are evaluated by two different methods. The activity obtained measuring the decay $$gamma$$-rays after 1912 shots at 1 Hz is 1.7$$pm$$0.2 Bq. This is in good agreement with 1.6$$pm$$0.3 Bq evaluated from the proton energy distribution measured using a time-of-flight detector and the nuclear reaction cross-sections. We conclude that the production of activity can be monitored in real time using the time-of-flight-detector placed inside a diverging proton beam coupled with a high-speed signal processing system.

Journal Articles

Development of computational method for predicting vortex cavitation in the reactor vessel of JSFR

Hamada, Noriaki*; Shiina, Koji*; Fujimata, Kazuhiro*; Hayakawa, Satoshi*; Watanabe, Osamu*; Yamano, Hidemasa

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 10 Pages, 2012/00

In a sodium-cooled fast reactor, a vortex cavitation evaluation methodology was developed to predict a possible cavitation generated by vortex at the center of accelerating flow. This methodology was applied to a scaled model experiment, leading to the prospect that the cavitation can be predicted.

Journal Articles

Unsteady elbow pipe flow to develop a flow-induced vibration evaluation methodology for JSFR

Yamano, Hidemasa; Tanaka, Masaaki; Ono, Ayako; Murakami, Takahiro*; Iwamoto, Yukiharu*; Yuki, Kazuhisa*; Sago, Hiromi*; Hayakawa, Satoshi*

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 12 Pages, 2012/00

This paper describes the current status of flow-induced vibration evaluation methodology development for primary cooling pipes in JSFR, in particular emphasizing on recent R&D activities that investigate unsteady elbow pipe flow. The experiment using the 1/3-scale test section was performed to investigate the effect of swirl flow at the inlet. Although the flow separation region was distorted at the downstream from the elbow, the experiment clarified that the effect of swirl flow on pressure fluctuation onto the pipe wall was not significant. The simulation revealed that Reynolds number scarcely affects flow patterns and flow velocity distributions.

Journal Articles

Unsteady elbow pipe flow to develop a flow-induced vibration evaluation methodology for Japan sodium-cooled fast reactor

Yamano, Hidemasa; Tanaka, Masaaki; Murakami, Takahiro*; Iwamoto, Yukiharu*; Yuki, Kazuhisa*; Sago, Hiromi*; Hayakawa, Satoshi*

Journal of Nuclear Science and Technology, 48(4), p.677 - 687, 2011/04

This paper describes the current status of flow-induced vibration evaluation methodology development for primary cooling pipes in Japan Sodium-cooled Fast Reactor (JSFR), in particular emphasizing on recent R&D activities that investigate unsteady elbow pipe flow.

Journal Articles

Reanalysis of the ($$J$$ = 5) state at 592 keV in $$^{180}$$Ta and its role in the $$nu$$-process nucleosynthesis of $$^{180}$$Ta in supernovae

Hayakawa, Takehito; Mohr, P.*; Kajino, Toshitaka*; Chiba, Satoshi; Mathews, G. J.*

Physical Review C, 82(5), p.058801_1 - 058801_4, 2010/11

 Times Cited Count:11 Percentile:61.84(Physics, Nuclear)

We analyze the production and freeze-out of the isomer $$^{180}$$Ta in the $$nu$$-process. We consider the influence of a possible low-lying intermediate ($$J$$ = 5) state at 592 keV using a transition width estimated from the measured half-life. This more realistic width is much smaller than the previous estimate. We find that the 592 keV state leads only to a small reduction of the residual isomer ratio from the previous result. The isomer ratio changes from 0.39 to 0.38, whereas previously it was estimated that this transition could reduce the ratio to R = 0.18. This finding strengthens the evidence that $$^{138}$$La and $$^{180}$$Ta are coproduced by neutrino nucleosynthesis with an electron neutrino temperature of ${it kT}$ $$approx$$ 4 MeV.

Journal Articles

Neutrino reactions on $$^{138}$$La and $$^{180}$$Ta via charged and neutral currents by the quasiparticle random-phase approximation

Cheoun, M. K.*; Ha, E.*; Hayakawa, Takehito; Kajino, Toshitaka*; Chiba, Satoshi

Physical Review C, 82(3), p.035504_1 - 035504_7, 2010/09

 Times Cited Count:36 Percentile:88.6(Physics, Nuclear)

We investigate neutrino-induced reactions on heavy nuclei. Charged current (CC) reactions,$$^{138}$$Ba($$nu_e$$, $$e$$$$^-$$)$$^{138}$$La and $$^{180}$$Hf($$nu_e$$, $$e$$$$^-$$)$$^{180}$$Ta are calculated by a quasi-particle random phase approximation (QRPA) with pairing correlations. For neutral current (NC) reactions, $$^{139}$$La($$nu,nu'$$)$$^{139}$$La$$^*$$ and $$^{181}$$Ta($$nu,nu'$$)$$^{181}$$Ta$$^*$$, we generate ground and excited states of odd-even target nuclei, $$^{139}$$La and $$^{181}$$Ta, by operating one quasi-particle to even-even nuclei. Numerical results for CC reactions are shown to be consistent with recent semi-empirical data deduced from the Gamow-Teller strength distributions measured in the ($$^3$$He,$$t$$) reaction. Results for NC reactions are estimated to be smaller by a factor about 4 to 5 rather than those by CC reactions. Finally, cross sections weighted by the incident neutrino flux in the core collapsing supernova are presented for further applications to the network calculations for relevant nuclear abundances.

Journal Articles

New estimate for the time-dependent thermal nucleosynthesis of $$^{180}$$Ta$$^{m}$$

Hayakawa, Takehito; Kajino, Toshitaka*; Chiba, Satoshi; Mathews, G. J.*

Physical Review C, 81(5), p.052801_1 - 052801_4, 2010/05

 Times Cited Count:44 Percentile:91.63(Physics, Nuclear)

The nucleosynthesis of $$^{180}$$Ta has remained an unsolved problem. The supernova neutrino process has been proposed as the origin of $$^{180}$$Ta but its model calculation overproduces the $$^{180}$$Ta solar abundance. This may originate from the unique feature that the naturally occurring abundance of $$^{180}$$Ta is actually a meta-stable isomer, while the ground state is beta-unstable. We have made a new time-dependent calculation of the supernova production ratio of the long-livedisomer in $$^{180}$$Ta. Such a time-dependent solution is crucial for understanding the production and survival of this isotope. We find that the explicit time evolution of the synthesis of $$^{180}$$Ta using the available nuclear data shows $$^{180}$$Ta can be produced by neutrino process and neutrino temperature of 4 MeV.

64 (Records 1-20 displayed on this page)