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Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.
Radiation Protection Dosimetry, 199(14), p.1620 - 1625, 2023/09
Times Cited Count:0 Percentile:0.01(Environmental Sciences)We have been conducting dose assessments for Japanese macaques captured in Fukushima to reveal radiobiological effects on the low-dose expose animals. To accurately determine the external exposure dose, it is desirable to examine the analysis of the CO radical intensity. We examined ESR spectra of teeth of 10 macaques captured in Fukushima by two spectrum-decomposition algorithms.
Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.
KEK Proceedings 2022-2, p.120 - 125, 2022/11
We investigate the effect of sample's anisotropy and measurement condition to obtain the higher reproducibility for the shape of the ESR spectrum and the intensity of CO radical.
Ishikawa, Ryoya*; Suzuki, Masatoshi*; Kino, Yasushi*; Endo, Satoru*; Nakajima, Hiroo*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Shinoda, Hisashi*; et al.
KEK Proceedings 2022-2, p.61 - 66, 2022/11
The balance between oxidative stress and antioxidant activity, which is a defense mechanism against oxidative stress, was investigated in the liver and bladder of wild Japanese macaques captured in Fukushima Prefecture. No significant induction of oxidative stress by exposure to environmental radionuclides after the Fukushima nuclear accident was observed, suggesting that the stress defense mechanism of the organism is activated in some organs.
Hayashi, Koichi*; Lederer, M.*; Fukumoto, Yohei*; Goto, Masashi*; Yamamoto, Yuta*; Happo, Naohisa*; Harada, Masahide; Inamura, Yasuhiro; Oikawa, Kenichi; Oyama, Kenji*; et al.
Applied Physics Letters, 120(13), p.132101_1 - 132101_6, 2022/03
Times Cited Count:0 Percentile:0(Physics, Applied)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.
Sasaki, Koei; Miura, Shuichiro*; Fukumoto, Kenichi*; Goto, Minoru; Ohashi, Hirofumi
Proceedings of 28th International Conference on Nuclear Engineering (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 1500C 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 1000C may be caused by evaporation of Cs (boiling point: 671C) was seen in the TG result of both specimens. Precipitated Cs-Sb substance in the graphite matrix were not resolved even after the 1500C heating. The chemical composition of the Cs-Sb was specified as CsSb. 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.
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:7 Percentile:42.63(Materials Science, Multidisciplinary)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:16 Percentile:64.97(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.
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
Times Cited Count:6 Percentile:50.47(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.
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:6 Percentile:39.89(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.
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.
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:33.7(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 Ne 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.
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:58.56(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 2.010 for the fundamental voltage, 1.010 for the fifth-harmonic voltage, and 1.910 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.
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:85.86(Physics, Fluids & Plasmas)no abstracts in English
Kinoshita, Chiken*; Abe, Hiroaki; *; Fukumoto, Kenichi*
Journal of Nuclear Materials, 219, p.152 - 160, 1995/00
Times Cited Count:13 Percentile:76.14(Materials Science, Multidisciplinary)no abstracts in English
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 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 C. Complicated microstructural dependence of nickel contents for Fe-15Cr-xNi alloys could be seen.
Kaburaki, Hideo; Suzudo, Tomoaki; Fukumoto, Kenichi*; Itakura, Mitsuhiro
no journal, ,
no abstracts in English
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.
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-5volPMMA and average bubble size was about 10 nm in diameter. It was analyzed that dispersed bubbles can strengthen copper with an angle 79 at dislocation detached from bubbles, which was consistent with the interaction angle 74 estimated by Vickers hardness measurement of the same specimen.
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.