Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 25

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

Development of dose estimation method using wild animal teeth for low dose exposure

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

KEK Proceedings 2021-2, p.91 - 96, 2021/12

We examined whether the ESR dose estimation method could be applied to wild Japanese macaque. In this work, we investigated the enamel preparation protocol and the analytical method of the ESR spectra.

Journal Articles

Development of cesium trap material for coated fuel particles in high temperature gas-cooled reactors

Sasaki, Koei; Miura, Shuichiro*; Fukumoto, Kenichi*; Goto, Minoru; Ohashi, Hirofumi

Proceedings of 28th International Conference on Nuclear Engineering; Nuclear Energy the Future Zero Carbon Power (ICONE 28) (Internet), 6 Pages, 2021/08

Cs-Bi and Cs-Sb absorbed graphite samples (Cs-Bi/graphite and Cs-Sb/graphite) were synthesized and their high temperature chemical stabilities were tested up to 1500$$^{circ}$$C by TG and analyzed by TEM-EDS for the development of Cs trap material in high temperature gas-cooled reactor (HTGR) fuel particles. It was observed that Cs was stabilized by Sb but not by Bi in the specimens after the TG test. A rapid weight loss from 800 to 1000$$^{circ}$$C may be caused by evaporation of Cs (boiling point: 671$$^{circ}$$C) was seen in the TG result of both specimens. Precipitated Cs-Sb substance in the graphite matrix were not resolved even after the 1500$$^{circ}$$C heating. The chemical composition of the Cs-Sb was specified as Cs$$_{3}$$Sb. The experimental results suggest that Sb have potential to be a Cs getter material in graphite matrix. Long term heating test should be performed to confirm adaptability of Sb for Cs trap material in HTGR fuel particles.

Journal Articles

Behavior of Sm in the boron cage of Sm-doped $$R$$B$$_{6}$$ ($$R$$ =Yb, La) observed by multiple-wavelength neutron holography

Uechi, Shoichi*; Oyama, Kenji*; Fukumoto, Yohei*; Kanazawa, Yuki*; Happo, Naohisa*; Harada, Masahide; Inamura, Yasuhiro; Oikawa, Kenichi; Matsuhra, Wataru*; Iga, Fumitoshi*; et al.

Physical Review B, 102(5), p.054104_1 - 054104_10, 2020/08

 Times Cited Count:2 Percentile:24.67(Materials Science, Multidisciplinary)

Journal Articles

Analyzing the cross slip motion of screw dislocations at finite temperatures in body-centered-cubic metals; Molecular statics and dynamics studies

Suzudo, Tomoaki; Onitsuka, Takashi*; Fukumoto, Kenichi*

Modelling and Simulation in Materials Science and Engineering, 27(6), p.064001_1 - 064001_15, 2019/08

 Times Cited Count:7 Percentile:63.45(Materials Science, Multidisciplinary)

Plasticity of body-centered-cubic (BCC) metals at low temperatures is determined by screw dislocation kinetics. Because the core of screw dislocation in these metals has non-planar structure, its motion is complex and unpredictable. For example, although density functional theory (DFT) predicts slip on a { 110 } plane, the actual slip plane at elevated temperatures departs from the prediction, its mechanism having been a mystery for decades. Here we conduct a series of molecular dynamics simulations to track the screw dislocation motion and successfully reproduced the transition of the slip plane. We then devised an algorithm to scrutinize the activation of dislocation jump over the Peierls barrier and discovered the possible origin of this unexpected phenomenon, i.e., a large fluctuation leads to the kink-pair nucleation for the cross-slip jump without transition of dislocation core structure.

Journal Articles

Cs-Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel

Sasaki, Koei; Fujimura, Ryota*; Tanigaki, Takanori; Matsubara, Masanori*; Fukumoto, Kenichi*; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 54(2), p.139 - 146, 2017/02

AA2016-0211.pdf:2.83MB

 Times Cited Count:3 Percentile:40.62(Nuclear Science & Technology)

In an attempt to investigate Cs-Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel, Cs-Te corrosion out-pile tests of two 9Cr steels with different distributions of chromium carbide were carried out at 975K for 100h and their corrosion depths were compared. The corrosion is obviously more advanced in a specimen which has grain boundary carbide than in the one that does not. A considerable reason of the result is that the carbide distributed at grain boundaries promoted the corrosion reaction and the corrosion extended along the grain boundary. This is the first case in which the Cs-Te corrosion depth dependence on distribution of chromium carbide precipitation in Fe-Cr steel is clarified experimentally.

Journal Articles

Development of irradiation capsules in liquid metal environment in Joyo and their application to irradiation creep measurement of vanadium alloys

Fukumoto, Kenichi*; Narui, Minoru*; Matsui, Hideki*; Ito, Kazuhiro; Yano, Yasuhide

Journal of Nuclear Science and Technology, 45(2), p.171 - 178, 2008/02

 Times Cited Count:5 Percentile:37.69(Nuclear Science & Technology)

In order to perform irradiation experiments under liquid metal environment in a nuclear reactor, an irradiation technique with sodium bonding irradiation capsules has been developed and a series of neutron irradiation experiments with sodium bonding irradiation capsule were performed in Joyo. The design and fabrication of sodium bonding capsule, sodium filling into capsules, capsule loading to Joyo, irradiation experiments, dismantling for irradiated capsule, removing the irradiated specimens from sodium filled capsules, and sodium cleaning the irradiated specimens were established through this study. Using the Joyo irradiation with the sodium bonding capsules where irradiation temperature was distributed uniformly, the irradiation creep experiment for highly purified V-4Cr-4Ti alloys, NIFS-Heat was carried out and the knowledge about the irradiation creep behavior of the alloys was obtained.

Journal Articles

Wideband low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron

Irie, Yoshiro; Dooling, J.*; Horan, D.*; Kustom, R.*; Middendorf, M.*; Pile, G.*; Bayley, D.*; Cross, G.*; Gardner, I.*; Glover, M.*; et al.

Proceedings of 10th European Particle Accelerator Conference (EPAC 2006) (CD-ROM), p.321 - 323, 2006/00

Wideband low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by the collaboration between ANL (US), KEK (Japan) and RAL (UK). Low output impedance is realized by the feedback from plate to grid of the final triode amplifier, resulting in less than 30 ohms over a wide frequency range of 2.7 - 6.2 MHz. The vacuum tubes in the driver and final stages are both operated in class A. High power test was performed with a ferrite-loaded second harmonic cavity, where the bias current was swept at 50 Hz repetition rate. The maximum voltage of 12 kV peak per accelerating gap was obtained stably at earlier period of an acceleration cycle. A beam test with this system is planned at the ISIS synchrotron soon.

Journal Articles

An Energy spread minimization system for microbeam generation in the JAERI AVF cyclotron

Fukuda, Mitsuhiro; Kurashima, Satoshi; Miyawaki, Nobumasa; Okumura, Susumu; Kamiya, Tomihiro; Oikawa, Masakazu*; Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; et al.

Nuclear Instruments and Methods in Physics Research B, 210, p.33 - 36, 2003/09

 Times Cited Count:4 Percentile:34.53(Instruments & Instrumentation)

A heavy ion microbeam with energy of hundreds MeV is a significantly useful probe for research in biotechnology. A single-ion hitting technique using a 260 MeV $$^{20}$$Ne$$^{7+}$$ microbeam is being developed at the JAERI AVF cyclotron facility for biofunction elucidation. Production of a microbeam with a spot size of one micro-meter in diameter requires reducing the energy spread of the beam to 0.02 % to minimize an effect of chromatic aberrations in focusing lenses. The typical energy spread of the cyclotron beam is around 0.1 % in an ordinary acceleration mode using a sinusoidal voltage waveform. The energy spread can be reduced by superimposing the fifth-harmonic voltage waveform on the fundamental one to generate a flattop waveform for uniform energy gain. We have designed an additional coaxial cavity to generate the fifth-harmonic voltage, coupled to the main resonator of one-fourth wavelength coaxial type. In a power test we successfully observed the fifth-harmonic voltage waveform by picking up an acceleration voltage signal.

Journal Articles

Flat-top acceleration system for the variable-energy multiparticle AVF cyclotron

Fukuda, Mitsuhiro; Kurashima, Satoshi; Okumura, Susumu; Miyawaki, Nobumasa; Agematsu, Takashi; Nakamura, Yoshiteru; Nara, Takayuki; Ishibori, Ikuo; Yoshida, Kenichi; Yokota, Wataru; et al.

Review of Scientific Instruments, 74(4), p.2293 - 2299, 2003/04

 Times Cited Count:14 Percentile:60.36(Instruments & Instrumentation)

A combination of the fundamental- and the fifth-harmonic voltages is ideally suited for flat-top acceleration in a variable-energy multi-particle cyclotron for energy-spread minimization. The flat-topping of the energy gain distribution using the fifth-harmonics has the advantages of minimizing an amplifier power, reducing power dissipation in a resonator and increasing the energy gain per turn. The flat-top acceleration system of the JAERI AVF cyclotron was designed to reduce the energy spread to 0.02 $$%$$, required for microbeam production. Tolerable fluctuations of acceleration voltages and the magnetic excitation were 2.0$$times$$10$$^{-4}$$ for the fundamental voltage, 1.0$$times$$10$$^{-3}$$ for the fifth-harmonic voltage, and 1.9$$times$$10$$^{-5}$$ for the magnetic field. In order to enhance compactness of the flat-topping cavity and to make a substantial saving of the amplifier power, optimum geometric parameters of the flat-topping cavity were determined by a cold model test and a calculation using the MAFIA code.

Journal Articles

Prepulse effects on the interaction of intense femtosecond laser pulses with high-Z solids

Zhidkov, A. G.; Sasaki, Akira; Utsumi, Takayuki*; Fukumoto, Ichiro; Tajima, Toshiki; Saito, Fumikazu*; Hironaka, Yoichiro*; Nakamura, Kazutaka*; Kondo, Kenichi*; Yoshida, Masataka*

Physical Review E, 62(5), p.7232 - 7240, 2000/11

 Times Cited Count:51 Percentile:86.88(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Effects of concurrent irradiation with ions and electrons on the formation process of defect clusters in covalent and ionic crystals

Kinoshita, Chiken*; Abe, Hiroaki; *; Fukumoto, Kenichi*

Journal of Nuclear Materials, 219, p.152 - 160, 1995/00

 Times Cited Count:13 Percentile:77.26(Materials Science, Multidisciplinary)

no abstracts in English

Oral presentation

Microstructural effect of solute addition for Fe-15Cr-20Ni steels irradiated in Joyo

Fukumoto, Kenichi*; Matsui, Hideki*; Akasaka, Naoaki; Yamagata, Ichiro

no journal, , 

The relationship between the addition of minor element and the swelling behavior was investigated using nine heats of Fe-15Cr-20Ni austenitic model alloys, Fe-15Cr-xNi(x = 20, 25 and 30) and a PNC1520 steel irradiated at 480, 570, 620 and 700 $$^{circ}$$C in the Joyo to doses of 20-56 dpa. Phosphorus and boron suppressed the appearance of swelling for these experimental irradiation conditions. Additions of titanium and niobium were effective for suppression of swelling at low temperature, below 570 $$^{circ}$$C. Complicated microstructural dependence of nickel contents for Fe-15Cr-xNi alloys could be seen.

Oral presentation

A Molecular dynamics study on the hardening mechanism due to void-dislocation interaction in vanadium

Kaburaki, Hideo; Suzudo, Tomoaki; Fukumoto, Kenichi*; Itakura, Mitsuhiro

no journal, , 

no abstracts in English

Oral presentation

Dynamical interaction between a screw dislocation and a void in pure iron using molecular dynamics

Okubo, Manabu*; Onitsuka, Takashi*; Fukumoto, Kenichi*; Suzudo, Tomoaki

no journal, , 

In structural materials of fast breeder and fusion rectors, vacancies produced by radiation displacements are clustered and form voids. Experimental evidence indicates that the voids become obstacles of dislocation motion and cause hardening of the materials, but the detailed mechanism of the hardening has not been clear. In the current study, we perform molecular dynamics simulation of the interaction between a screw dislocation and a void to clarify the radiation hardening mechanism. Our results clearly show that the screw dislocation is pinned between the center of the void and its rear interface.

Oral presentation

In-situ TEM observation under tensile loading in bubble dispersion strengthen copper

Shi, S.*; Ono, Naoko*; Ukai, Shigeharu*; Hayashi, Shigenari*; Togo, Koichi*; Fukumoto, Kenichi*; Abe, Yosuke

no journal, , 

Bubble dispersion strengthened (BDS) copper was synthesized by using the dissociated gases of the poly methyl methacrylate (PMMA) during Spark Plasma Sintering (SPS). By in-situ TEM observation under tensile loading, we analyzed a detachment angle of the dislocation from the bubble, and evaluated the pinning force of bubble for the moving dislocations. TEM observation showed homogeneously dispersed bubbles in Cu-5vol$$%$$PMMA and average bubble size was about 10 nm in diameter. It was analyzed that dispersed bubbles can strengthen copper with an angle 79$$^{circ}$$ at dislocation detached from bubbles, which was consistent with the interaction angle 74$$^{circ}$$ estimated by Vickers hardness measurement of the same specimen.

Oral presentation

Analyses of dynamic interactions between void and screw dislocation in BCC metals using molecular dynamics

Onitsuka, Takashi*; Okubo, Manabu*; Fukumoto, Kenichi*; Suzudo, Tomoaki

no journal, , 

Many of BCC metals are used as structural materials in nuclear devices. A possible cause of embrittlement of such metals under neutron radiation is accumulation of lattice defects that hamper the dislocation motions. Molecular dynamics have been used for the analyses of such dislocation motions, but interaction mechanism between the lattice defects and screw dislocation are still unclear. In this talk, we utilize molecular dynamics and analyze the interaction between void and screw dislocation in BCC Fe.

Oral presentation

Molecular dynamics studies on interaction between a screw dislocation and a void in pure Fe, 2

Onitsuka, Takashi*; Okubo, Manabu*; Suzudo, Tomoaki; Fukumoto, Kenichi*

no journal, , 

Reactor structural materials such as pressure vessels become brittle under neutron irradiation. It is widely known that a cause of such phenomenon could be formation of extended lattice defects under irradiation such as voids that become obstacles for dislocation motion, but we do not know the strength of these obstacles accurately enough for establishing a quantitative model. In the present study, we choose pure iron as a substitute of steel and numerically simulate the interaction between screw dislocation and a void using molecular dynamics method. Especially, we analyze the critical shear stress.

Oral presentation

Molecular dynamics studies on interaction between a screw dislocation and a void in pure Fe, 5

Taniguchi, Keisuke*; Onitsuka, Takashi*; Fukumoto, Kenichi*; Suzudo, Tomoaki

no journal, , 

It is known that a cause of irradiation hardening of nuclear materials by neutron irradiation can be ascribed to voids as an obstacle against dislocation motion. In this research, molecular dynamics (MD) simulations were exploited in order to analyze the dynamical reaction mechanism at the atomic level of the screw dislocation and void in BCC pure Fe. In particular, the relationship between the dislocation-void contact position and the strength of interaction was analyzed. As a result, it turned out that there is a rule between the contact position and the shear stress.

Oral presentation

Incorporation record of radionuclides in teeth and otoliths

Koarai, Kazuma; Matsueda, Makoto; Fujiwara, Kenso; Ono, Takumi*; Kino, Yasushi*; Oka, Toshitaka; Okutsu, Kenichi*; Takahashi, Atsushi*; Suzuki, Toshihiko*; Shimizu, Yoshinaka*; et al.

no journal, , 

We have investigated incorporation of $$^{90}$$Sr and $$^{137}$$Cs in teeth of cattle and otoliths of fish. Specific activity of $$^{90}$$Sr in the dentin tissue was higher than that in the enamel tissue. The result shows change of $$^{90}$$Sr incorporation in cattle even within a tooth. Concentrations of stable Sr and Cs were 94 ppm and 3 ppb. Distributions of stable Sr and Cs were uniform in the otolith of fish. If distribution of $$^{90}$$Sr and $$^{137}$$Cs in the otolith was measured, change of $$^{90}$$Sr and $$^{137}$$Cs incorporation into the fish would be found. These findings suggest that distribution patterns of $$^{90}$$Sr and $$^{137}$$Cs in the environment could be estimated from distribution of the radionuclides in the tooth and otolith.

Oral presentation

Screw dislocation behavior in BCC Fe; Study using molecular dynamics simulations

Suzudo, Tomoaki; Onitsuka, Takashi*; Fukumoto, Kenichi*

no journal, , 

The irradiation produces various defects such as dislocation loops, voids, and solute clusters. Since they become obstacles for dislocations, research on the interaction between dislocations and obstacles has been pursued. Regarding the slip plane of BCC iron, the slip plane is {110} at low temperature but changes to {112} when the temperature increases to about room temperature; however, this phenomena has not been reproduced by molecular dynamics. We reconsidered the interatomic potential to reproduce the above temperature transition of the slip plane by molecular dynamics. In addition, the mechanism of the transition was discussed from the Peierls potential of the screw dislocation. As a result, it was found that the temperature transition of the slip plane can be reproduced by selecting an appropriate interatomic potential. It was also found that the temperature transition was likely to have been caused by temperature fluctuations of the lattice.

25 (Records 1-20 displayed on this page)