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Sakamoto, Kan*; Sakaguchi, Chisato*; Miura, Yusuke*; Yokoyama, Hironori*; Matsunaga, Junji*; Kasahara, Hideyuki*; Miyata, Hajime*; Ioka, Ikuo; Yamashita, Shinichiro; Osaka, Masahiko
Proceedings of 2023 Water Reactor Fuel Performance Meeting (WRFPM 2023), p.20 - 28, 2024/00
An oxide-dispersion-strengthened FeCrAl (FeCrAl-ODS) has been continuously developed in Japan as a promising candidate alloy for the accident tolerant fuel cladding of BWRs (boiling water reactors). This paper will introduce the progress in practical development of accident tolerant FeCrAl-ODS fuel claddings for BWRs in the program fully or partially supported and organized by the Ministry of Economy, Trade and Industry (METI) of Japan. The experimental studies have been conducted to obtain and accumulate key material properties of FeCrAl-ODS fuel claddings to support the evaluations in the analytical studies. For the evaluation at normal operation condition, fatigue test of unirradiated fuel cladding and tensile test of irradiated sheet specimen were conducted. In the fatigue test, a tensile-compressive bending strain was loaded on the C-shaped specimens by cyclic movement of a push-pull rod. Test temperature was 623 K, frequency was 1 Hz, and strain amplitude were 0.27, 0.34 and 0.55 %. The results of fatigue tests demonstrated that cycles to failure of the FeCrAl-ODS cladding were higher than that of the O'Donnell and Langer fatigue curve of Zr-based alloy. The tensile test was conducted in a hot cell using the SS-J2 type specimens at ambient temperature, 573 K and 623 K at a strain rate of 10-3 s-1. The specimens were irradiated up to 7.8 and 13 dpa at 573 K in the High Flux Isotope Reactor at ORNL. The irradiation hardening and ductility loss obtained at 7.8 and 13 dpa were comparable to those at 3.9 dpa.
Ni
In
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Kotegawa, Hisashi*; To, Hideki*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.
Physical Review B, 106(23), p.235152_1 - 235152_8, 2022/12
Times Cited Count：1 Percentile：5.58(Materials Science, Multidisciplinary)We investigate the electronic state of Ni-substituted CeCoNi
In by nuclear quadrupole and magnetic resonance (NQR/NMR) techniques. The heavy fermion superconductivity below 
K for 
is suppressed by Ni substitutions, and 
reaches zero for 
. The 
In NQR spectra for 
and 0.25 can be explained by simulating the electrical field gradient that is calculated for a virtual supercell with density functional theory. The spin-lattice relaxation rate 
indicates that Ni substitution weakens antiferromagnetic correlations that are not localized near the substituent but instead are uniform in space. The temperature (
) dependence of 
for shows a maximum around 
K and decreases toward almost zero when temperature is further reduced as if a gap might be opening in the magnetic excitation spectrum; however, the magnetic specific heat and the static magnetic susceptibility evolve smoothly through 
with a 
dependence. The peculiar T dependence of and non-Fermi-liquid specific heat and susceptibility can be interpreted in a unified way by assuming nested antiferromagnetic spin fluctuations in a quasi-two-dimensional electronic system.
; In NQR/NMR and 
Co NMR studySakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Ramakrishna, S. K.*; Reyes, A. P.*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.
Physical Review B, 104(8), p.085106_1 - 085106_12, 2021/08
Times Cited Count：5 Percentile：26.77(Materials Science, Multidisciplinary)Antiferromagnetism in a prototypical quantum critical metal CeCoIn is known to be induced by slight substitutions of non-magnetic Zn atoms for In. In nominally 7% Zn substituted CeCoIn, an antiferromagnetic (AFM) state coexists with heavy fermion superconductivity. Heterogeneity of the electronic states is investigated in Zn doped CeCoIn by means of nuclear quadrupole and magnetic resonances (NQR and NMR). Site-dependent NQR relaxation rates indicate that the AFM state is locally nucleated around Zn substituents in the matrix of a heavy fermion state, and percolates through the bulk at the AFM transition temperature 
. At lower temperatures, an anisotropic superconducting (SC) gap below the SC transition temperature , and the SC state permeates through the AFM regions via a SC proximity effect. Applying an external magnetic field induces a spin-flop transition near 5 T, reducing the volume of the AFM regions. Consequently, a short ranged inhomogeneous AFM state survives and coexists with a paramagnetic Fermi liquid state at high fields.
Hashimoto, Masashi; Oba, Hironori; Yokoyama, Atsushi
Applied Physics B, 104(4), p.969 - 974, 2011/09
Times Cited Count：1 Percentile：6.80(Optics)Oxygen isotope separation has been examined by utilizing the two-frequency infrared multiphoton dissociation (IRMPD) of 2,3-dihydropyran (DHP). The two-frequency IRMPD reduces remarkably the required laser fluence. For example, dissociation probability of DHP containing 
O (D(O)) and enrichment factor (S) were obtained to be 1.6
10
/pulse and 316 respectively by the simultaneous irradiation with 1052.2 cm
photons at 0.45 J/cm
and 1031.5 cm photons at 1.06 J/cm. These are comparable with D(O) = 2.210 /pulse and S = 391 obtained by the single-frequency irradiation of 1033.5 cm photons at 2.2 J/cm. Therefore, the production rate of an O enriched dissociation product has been increased to four times or more, compared with the single-frequency IRMPD, and this two-frequency method would promise a practical large scale separation.
Oba, Hironori; Saeki, Morihisa; Esaka, Fumitaka; Yamada, Yoichi; Yamamoto, Hiroyuki; Yokoyama, Atsushi
Journal of the Vacuum Society of Japan, 52(6), p.369 - 371, 2009/07
no abstracts in English
Oba, Hironori; Suzuki, Hiroshi*; Esaka, Fumitaka; Taguchi, Tomitsugu; Yamada, Yoichi; Yamamoto, Hiroyuki; Sasase, Masato*; Yokoyama, Atsushi
Journal of the Vacuum Society of Japan, 52(6), p.292 - 295, 2009/07
no abstracts in English
Akagi, Hiroshi; Oba, Hironori; Yokoyama, Keiichi; Yokoyama, Atsushi; Egashira, Kazuhiro*; Fujimura, Yo*
Applied Physics B, 95(1), p.17 - 21, 2009/04
Times Cited Count：8 Percentile：39.60(Optics)We have proposed a laser isotope separation method, utilizing rotational coherence of a simple molecule. In the scheme, photoexcited molecules are isotopically separated by difference of rotational period between them. To illustrate this method, two-pulse photodissociation of mixed 
Br
/
Br isotopes has been investigated theoretically. The photodissociation probabilities of Br and Br have been calculated as a function of time delay between the photoexcitation and dissociation laser pulses. We have demonstrated that isotope enrichment factor of Br relative to Br can be changed from 0.34 to 1.8, by simply changing the time delay only by 0.2 ns. Additionally, we have shown that this method is effective for heavy isotopes, based on mass dependence of the isotope enrichment factor.
Nogiwa, Kimihiro; Nishimura, Akihiko; Oba, Hironori; Yokoyama, Atsushi; Okubo, Tadakatsu*; Hono, Kazuhiro*
Materia, 47(12), P. 626, 2008/12
no abstracts in English
Oba, Hironori; Akagi, Hiroshi; Katsumata, Keiichi*; Hashimoto, Masashi; Yokoyama, Atsushi
Japanese Journal of Applied Physics, 47(11), p.8379 - 8381, 2008/11
Times Cited Count：4 Percentile：18.11(Physics, Applied)This paper presents a practical method for producing highly enriched silicon isotopes utilizing laser irradiation. One- or two-frequency CO laser irradiation has been employed to separate the desired isotope of silicon by means of infrared multi-photon dissociation (IRMPD) of the hexafluorodisilane (SiF
) molecules using a flow reaction system. The production of SiF with 
Si fraction of 99.1% at a rate of 0.67 g(Si)/h was successfully accomplished with a high yield by the two-frequency laser irradiation. The enriched SiF
gas with 
Si exceeding 31% was also continuously obtained at the production rate of 0.12 g/h by the one-frequency laser irradiation.
Yokoyama, Atsushi; Katsumata, Keiichi*; Oba, Hironori; Akagi, Hiroshi; Saeki, Morihisa; Yokoyama, Keiichi
Journal of Physical Chemistry A, 112(29), p.6571 - 6577, 2008/07
Times Cited Count：5 Percentile：14.97(Chemistry, Physical)Oxygen isotope separation has been examined by using an infrared multiphoton dissociation of 2,3-dihydropyran. Enrichment factor has been measured by the CO laser irradiation of the samples as a function of laser frequency, laser fluence, and sample pressure. Maximum enrichment factor of 751 has been obtained, and O, natural abundance of which is 0.205 %, was enriched to 60 %. Moreover, it was found that the enrichment factor increases with increasing the sample pressure, which was different from the infrared multiphoton dissociation of usual molecules. This phenomenon was discussed on the basis of a simulation by a rate equation model including a collisional vibrational relaxation.
Yamada, Yoichi; Yamamoto, Hiroyuki; Oba, Hironori; Sasase, Masato*; Esaka, Fumitaka; Yamaguchi, Kenji; Udono, Haruhiko*; Shamoto, Shinichi; Yokoyama, Atsushi; Hojo, Kiichi
Journal of Physics and Chemistry of Solids, 68(11), p.2204 - 2208, 2007/11
Times Cited Count：6 Percentile：30.02(Chemistry, Multidisciplinary)Si in natural Si has been widely used for a doping source, since Si can be transmuted into 
P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from Si-enriched materials can serve as a controlled local doping method with tunable dopant concentration, which cannot be realized by conventional doping methods such as ion implantation. In the present study, Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using Si-enriched SiF as the source gases. The film contains 7.1 % of Si, which is twice higher than that of natural Si. Possible contaminant, fluorine, is lower than 0.6 at.% determined from X-ray photoelectron spectra. Nanostructure of films and changes of electronic properties by the neutron irradiation will also be discussed.
Saeki, Morihisa; Oba, Hironori; Yokoyama, Atsushi
Journal of Physics; Conference Series, 59, p.732 - 735, 2007/00
Times Cited Count：0 Percentile：0.00(Optics)We have performed laser ablation of silicon in neon gas and benzene vapor. The reaction mechanism of the ablated silicon atoms with the neon atoms and benzene molecules were investigated by space- and time-resolved emission spectroscopy. The ablation in the neon gas suggested that (1) the neutral neon atoms are excited to 2pn states lying in 18-19 eV and (2) the neutral neon atoms are excited by electronic-to-electronic and translational-to-electronic energy transfer from the silicon ions. In the ablation in the benzene vapor, we found that the benzene molecules are decomposed into C2 and CH radicals by the collision with the silicon atoms.
Saeki, Morihisa; Hirata, Koichi*; Sakka, Tetsuo*; Oba, Hironori; Yokoyama, Atsushi
Journal of Applied Physics, 98(4), p.044912_1 - 044912_6, 2005/08
Times Cited Count：3 Percentile：13.24(Physics, Applied)no abstracts in English
Oba, Hironori; Saeki, Morihisa; Yokoyama, Atsushi
Proceedings of Plasma Science Symposium 2005/22nd Symposium on Plasma Processing (PSS-2005/SPP-22), p.331 - 332, 2005/01
A plasma produced by a XeCl laser ablation of boron compound was investigated using ion probes and a quadrupole mass spectrometer. Although the ablated neutral boron atoms had a natural abundance ratio, the isotope ratio of singly ionized boron atoms having a greatly different from the natural abundance ratio was observed. The observed isotope ratio of boron ions was different from the natural abundance.
F irradiated with two-frequency CO laser lightsYokoyama, Atsushi; Oba, Hironori; Hashimoto, Masashi; Katsumata, Keiichi; Akagi, Hiroshi; Ishii, Takeshi*; Oya, Akio*; Arai, Shigeyoshi*
Applied Physics B, 79(7), p.883 - 889, 2004/11
Times Cited Count：10 Percentile：43.88(Optics)Silicon isotope separation has been done utilizing the Infrared Multiphoton Dissociation of SiF irradiated with two-frequency CO laser lights. The two-frequency excitation method improved the separation efficiency with keeping the high enrichment factors. For example, SiF with the Si fraction of 99.4 % was obtained at 40.0 % dissociation of SiF after the simultaneous irradiation of 100 pulses with 966.23 cm photons (0.089 J/cm) and 954.55 cm photons (0.92 J/cm), while 1000 pulses were needed to obtain 99.0 % of Si at 27.2 % dissociation in the case of single frequency irradiation at 954.55 cm (0.92 J/cm). The single-step enrichment factors of 
Si and Si increased with increasing SiF pressure. The reason for this enhancement has been discussed in terms of the rotational and vibrational relaxations by collisions with ambient gases.
Si by infrared multiple photon decomposition of SiFYokoyama, Atsushi; Oba, Hironori; Shibata, Takemasa; Kawanishi, Shunichi*; Sugimoto, Shunichi*; Ishii, Takeshi*; Oya, Akio*; Miyamoto, Yoshiki*; Isomura, Shohei*; Arai, Shigeyoshi*
Journal of Nuclear Science and Technology, 39(4), p.457 - 462, 2002/04
Times Cited Count：3 Percentile：22.50(Nuclear Science & Technology)no abstracts in English
FOba, Hironori; Akagi, Hiroshi; Yokoyama, Atsushi; Yamada, Yoichi; Yamamoto, Hiroyuki
no journal, ,
no abstracts in English
Si-enriched thin film for local neutron transmutation dopingYamada, Yoichi; Yamamoto, Hiroyuki; Oba, Hironori; Sasase, Masato*; Esaka, Fumitaka; Yamaguchi, Kenji; Udono, Haruhiko*; Shamoto, Shinichi; Yokoyama, Atsushi; Hojo, Kiichi
no journal, ,
Si in natural Si has been widely used for a doping source, since Si can be transmuted into P by thermal neutron (Neutron Transmutation Doping, NTD). In the present study, Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using Si-enriched SiF as the source gases. Nanostructure of films and changes of electronic properties by the neutron irradiation will be discussed.
Saeki, Morihisa; Oba, Hironori; Yamada, Yoichi; Yamamoto, Hiroyuki; Esaka, Fumitaka; Yokoyama, Atsushi
no journal, ,
no abstracts in English
Yokoyama, Atsushi; Oba, Hironori; Yamada, Yoichi; Yamamoto, Hiroyuki
no journal, ,
no abstracts in English
