Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Futemma, Akira; Sanada, Yukihisa; Nagakubo, Azusa; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Akutsu, Yuichiro*; Arai, Yoshinori*; et al.
JAEA-Technology 2023-027, 146 Pages, 2024/03
JAEA-Technology-2023-027.pdf:18.12MB
By the accident at Tokyo Electric Power Company's (TEPCO's) Fukushima Daiichi Nuclear Power Station (FDNPS), caused by tsunami triggered by the 2011 off the Pacific coast of Tohoku Earthquake, a large amount of radioactive material was released into the surrounding environment. After the accident, Airborne Radiation Monitoring (ARM) via manned helicopter has been applied as a method to quickly and extensively measure the distribution of radiation. Japan Atomic Energy Agency (JAEA) has continuously conducted ARM via manned helicopter around FDNPS. In this report, we summarize the results of the ARM around FDNPS in the fiscal year 2022, evaluate the changes of ambient dose rates and other parameters based on the comparison to the past ARM results, and discuss the causes of such changes. In order to contribute to improve the accuracy of ambient dose rate conversion, we analyzed the ARM data taking into account undulating topography, and evaluated the effect of this method. Furthermore, the effect of radon progenies in the air on the ARM was evaluated by applying the discrimination method to the measurement results.
Futemma, Akira; Sanada, Yukihisa; Sasaki, Miyuki; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Akutsu, Yuichiro*; Arai, Yoshinori*; et al.
JAEA-Technology 2023-026, 161 Pages, 2024/03
JAEA-Technology-2023-026.pdf:14.66MB
By the accident at Tokyo Electric Power Company's (TEPCO's) Fukushima Daiichi Nuclear Power Station (FDNPS), caused by tsunami triggered by the 2011 off the Pacific coast of Tohoku Earthquake, a large amount of radioactive material was released into the surrounding environment. After the accident, Airborne Radiation Monitoring (ARM) via manned helicopter has been utilized as a method to quickly and extensively measure radiation distribution surrounding FDNPS. In order to utilize ARM and to promptly provide the results during a nuclear emergency, information on background radiation levels, topographical features, and controlled airspace surrounding nationwide nuclear facilities have been prepared in advance. In the fiscal year 2022, we conducted ARM around the Mihama Nuclear Power Station of Kansai Electric Power Company (KEPCO), the Tsuruga Power Station of Japan Atomic Power Company (JAPC), and the Ikata Power Station of Shikoku Electric Power Company (YONDEN), and prepared information on background radiation doses and controlled airspace. In addition, we have developed an aerial radiation detection system via unmanned airplane, which is expected to be an alternative to ARM, during a nuclear emergency. This report summarizes the results and technical issues identified.
Arai, Yosuke*; Kuroda, Kenta*; Nomoto, Takuya*; Tin, Z. H.*; Sakuragi, Shunsuke*; Bareille, C.*; Akebi, Shuntaro*; Kurokawa, Kifu*; Kinoshita, Yuto*; Zhang, W.-L.*; et al.
Nature Materials, 21(4), p.410 - 415, 2022/04
Times Cited Count：8 Percentile：75.56(Chemistry, Physical)Kuroda, Kenta*; Arai, Yosuke*; Rezaei, N.*; Kunisada, So*; Sakuragi, Shunsuke*; Alaei, M.*; Kinoshita, Yuto*; Bareille, C.*; Noguchi, Ryo*; Nakayama, Mitsuhiro*; et al.
Nature Communications (Internet), 11, p.2888_1 - 2888_9, 2020/06
Times Cited Count：21 Percentile：74.83(Multidisciplinary Sciences)Su, Y. H.; Oikawa, Kenichi; Kawasaki, Takuro; Kai, Tetsuya; Shiota, Yoshinori*; Sato, Hirotaka*; Shinohara, Takenao; Tomota, Yo*; Harada, Masahide; Kiyanagi, Ryoji; et al.
JPS Conference Proceedings (Internet), 8, p.031015_1 - 031015_5, 2015/09
In this study, neutron imaging experiment was performed using NOBORU, BL10 of MLF at J-PARC. Four kinds of cast duplex stainless steel with ferrite and austenite microstructure were studied here, which were produced by different casting method at different temperature. Firstly, two-dimensional scintillation detector using wavelength-shifting fibers with pixel size of 0.52 mm 
0.52 mm and illuminated area 55 mm 55 mm was used for data collection. Then, measurement by Micro Pixel Chamber based neutron imaging detector having higher spatial resolution about 0.2 mm was conducted. Data analysis code RITS (Rietveld Imaging of Transmission Spectra) will be used for microstructure including crystalline phase, lattice strain, crystallite size, texture evaluation.
Hattori, Takanori; Sano, Asami; Arima, Hiroshi*; Komatsu, Kazuki*; Yamada, Akihiro*; Inamura, Yasuhiro; Nakatani, Takeshi; Seto, Yusuke*; Nagai, Takaya*; Utsumi, Wataru; et al.
Nuclear Instruments and Methods in Physics Research A, 780, p.55 - 67, 2015/04
Times Cited Count：75 Percentile：98.98(Instruments & Instrumentation)PLANET is a time-of-flight (ToF) neutron beamline dedicated to high-pressure and high-temperature experiments. The large six-axis multi-anvil high-pressure press designed for ToF neutron diffraction experiments enables routine data collection at high pressures and high temperatures up to 10 GPa and 2000 K, respectively. To obtain clean data, the beamline is equipped with the incident slits and receiving collimators to eliminate parasitic scattering from the high-pressure cell assembly. The high performance of the diffractometer for the resolution (
/ 
0.6%) and the accessible -spacing range (0.2-8.4 
) together with low-parasitic scattering characteristics enables precise structure determination of crystals and liquids under high pressure and temperature conditions.
Haga, Yoshinori; Homma, Yoshiya*; Aoki, Dai*; Nakajima, Kunihisa; Arai, Yasuo; Matsuda, Tatsuma; Ikeda, Shugo*; Sakai, Hironori; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of the Physical Society of Japan, 81(Suppl.B), p.SB007_1 - SB007_4, 2012/12
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)Nakajima, Kunihisa; Serizawa, Hiroyuki; Shirasu, Noriko; Haga, Yoshinori; Arai, Yasuo
Journal of Nuclear Materials, 419(1-3), p.272 - 280, 2011/12
Times Cited Count：24 Percentile：85.52(Materials Science, Multidisciplinary)The solubility and diffusion coefficient of helium in the single-crystal UO
samples were determined by a Knudsen-effusion mass-spectrometric method. The measured helium solubilities were found to lie within the scatter of the available data, but to be much lower than those for the polycrystalline samples. The diffusion analysis was conducted based on a hypothetical equivalent sphere model and the simple Fick's law. The helium diffusion coefficient was determined by using the pre-exponential factor and activation energy as the fitting parameters for the measured and calculated fractional releases of helium. The optimized diffusion coefficients were in good agreement with those obtained by a nuclear reaction method reported in the past. It was also found that the pre-exponential factors of the determined diffusion coefficients were much lower than those analyzed in terms of a simple interstitial diffusion mechanism.
Arai, Yasuo; Serizawa, Hiroyuki; Nakajima, Kunihisa; Takano, Masahide; Sato, Isamu; Katsuyama, Kozo; Akie, Hiroshi; Suzuki, Motoe; Shirasu, Noriko; Haga, Yoshinori; et al.
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 8 Pages, 2011/12
High amount of He is generated in MA-bearing fuel during irradiation and storage periods compared with that in U or U-Pu fuel. Laboratory scale experiments, post irradiation examinations and modeling study were carried out in order to understand the He behavior in MA-bearing oxide fuel. Diffusion characteristics of He in single-crystal UO were investigated by the Knudsen effusion mass spectrometry. Effects of the He accumulation on lattice and bulk expansion of oxide pellets were examined by use of alpha-decay of 
Cm. Post irradiation examinations of 0.5%Am-MOX fuel irradiated at a fast test reactor JOYO were carried out, concentrating on the He behavior in the fuel pellets. A model describing the He behavior in MA-MOX fuel was constructed based on the principle processes, such as generation, diffusion, equilibrium and release to outer gaseous phase. By use of the model as a subroutine of a conventional fuel behavior analysis code, the He behavior in MA-MOX fuel for fast reactors was simulated.
AlHaga, Yoshinori; Homma, Yoshiya*; Aoki, Dai*; Ikeda, Shugo*; Matsuda, Tatsuma; Tateiwa, Naoyuki; Yamamoto, Etsuji; Nakamura, Akio; Nakajima, Kenji; Arai, Yasuo; et al.
IOP Conference Series; Materials Science and Engineering, 9, p.012046_1 - 012046_7, 2010/05
Times Cited Count：0 Percentile：1.02(Chemistry, Inorganic & Nuclear)Imai, Nobuaki*; Jeong, S.-C.*; Oyaizu, Mitsuhiro*; Arai, Shigeaki*; Fuchi, Yoshihide*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Miyatake, Hiroari; Tanaka, Masahiko*; Okada, Masayuki*; et al.
Review of Scientific Instruments, 79(2), p.02A906_1 - 02A906_3, 2008/02
Times Cited Count：13 Percentile：51.61(Instruments & Instrumentation)KEKCB is an 18 GHz Electron Cyclotron Resonance (ECR) ion source and is a charge breeder device for converting mass-separated 1
radioactive ions to multi-ionized ones by utilizing an axial injection technique to the ECR plasma. It is a part of the Tokai Radioactive Ion Accelerator Complex (TRIAC) facility. Based on the developments so far, converting efficiencies for metal elements, such as barium and indium, and for gaseous elements, such as krypton and xenon, are improved to be 7 
and 2 , respectively. And it is confirmed that the efficiency is nearly the constant for short-lived (t
1 sec) isotopes. Background ions mixed in the output beams are supressed to be 600 pps from 10
pps by applying all aluminum electrodes and high pressure pure-water cleanings.
Sakai, Hironori; Kambe, Shinsaku; Tokunaga, Yo; Fujimoto, Tatsuya; Walstedt, R. E.*; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of Physics and Chemistry of Solids, 68(11), p.2103 - 2106, 2007/11
Times Cited Count：1 Percentile：7.44(Chemistry, Multidisciplinary)A lot of attention is currently focused on Pu-based superconductors. These systems have relatively high superconducting (SC) transition temperatures, 
18 K for PuCoGa and 9 K for PuRhGa. Both compounds crystallize in the tetragonal HoCoGa (115) structure, which is well known for the heavy-fermion SC systems Ce
In (=Co, Rh, Ir)with 
2 K at most. Recently, NMR and NQR experiments have been reported for PuCoGa by Curro et al. and for PuRhGa by our group. In both cases, measurements of 
using NQR have revealed that the Pu115 superconductors show unconventional superconductivity with an anisotropic gap. Now we have measured the more detailed data of for NQR lines in PuRhGa, especially focusing on the low-lying magnetic excitation in the normal state. From the viewpoint of spin-fluctuations, we will discuss the difference between PuRhGa and PuCoGa and between superconducting Pu115 and non-superconducting An115 series.
Tokunaga, Yo; Sakai, Hironori; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.*; Ikushima, Kenji*; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Haga, Yoshinori; et al.
Journal of Alloys and Compounds, 444-445, p.241 - 245, 2007/10
Times Cited Count：19 Percentile：68.7(Chemistry, Physical)In this paper, we present our recent NMR works on Neptunium and Plutonium compounds. In order to elucidate the nature of the exotic multipolar ordered phase of NpO
, we have initiated the first NMR measurements on this system. We have shown that direct observation of multipole order parameters is possible by means of NMR. Our NMR results provide further insight into the microscopic nature of multipole phase transitions in f-electron systems. We have also performed 
Ga NMR/NQR studies on a single crystal of PuRhGa. From the temperature dependence of the spin-lattice relaxation rate (
), we have found that PuRhGa is an unconventional superconductor having an anisotropic superconducting (SC) gap 2
=5
. Furthermore, we have confirmed the Knight shift to be decreased below 
. This gives strong evidence for spin singlet SC pairing.
Haga, Yoshinori; Aoki, Dai*; Yamagami, Hiroshi*; Matsuda, Tatsuma; Nakajima, Kunihisa; Arai, Yasuo; Yamamoto, Etsuji; Nakamura, Akio; Homma, Yoshiya*; Shiokawa, Yoshinobu*; et al.
Journal of Alloys and Compounds, 444-445, p.114 - 118, 2007/10
Times Cited Count：3 Percentile：28.04(Chemistry, Physical)We report the first dHvA study in plutonium compound PuIn
with the cubic AuCu type structure, which can be regarded as a reference compound of PuCoGa. The result of the angular dependence of the dHvA frequency, which corresponds to the extremal cross section of the Fermi surface perpendicular to the field direction, was analyzed by the band calculations. The experimental data agree well with the theory, indicating that the 5f electrons can be treated as itinerant ones. The experimental dHvA study for plutonium-based superconductors such as PuCoGa are also desired but more challenging because the superconducting mixed state extremely weaken the dHvA amplitude.
:NQR relaxation studySakai, Hironori; Kambe, Shinsaku; Tokunaga, Yo; Fujimoto, Tatsuya; Walstedt, R. E.*; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e118 - e119, 2007/03
The spin-lattice relaxation rates () have been measured under zero fieldusing nuclear quadrupole resonance (NQR) linesin superconductor PuRhGa and Pauli-paramagnet LuCoGa. In the reference LuCoGa with fully-occupied 
shell, the shows the constant behavior of 
(sec
K)
. On the other hand, in PuRhGa, is much larger than in LuCoGaand the 
behavior below 30 K is seen, where its 
value is 3.27 
0.005 (secK). These results suggest a development of coherent Fermi liquid stateincorporated with 
electronsbelow 30 K in PuRhGa.
Haga, Yoshinori; Aoki, Dai*; Yamagami, Hiroshi*; Matsuda, Tatsuma; Nakajima, Kunihisa; Arai, Yasuo; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e149 - e151, 2007/03
Single crystals of plutonium compounds PuRhGa and PuIn are successfully grown. For PuRhGa, anisotropy of the supercon- ducting upper critical field was found and analyzed by the anisotropic mass model, consistent with quasi-two-dimensional electronic states predicted by band calculations. On the other hand, the de Haas-van Alphen oscillation was observed in PuIn. By comparing with the band calculations, it is concluded that 5f electrons are itinerant in PuIn.
superconductivity"Arai, Masatoshi; Yokoo, Tetsuya*; Kajimoto, Ryoichi; Nakajima, Kenji; Shamoto, Shinichi; Yamada, Kazuyoshi*; Fujita, Masaki*; Ino, Takashi*; Soyama, Kazuhiko; Nakamura, Mitsutaka; et al.
JAEA-Review 2006-033, 58 Pages, 2006/11
JAEA-Review-2006-033.pdf:17.22MB
A research project entitled "Development of the 4D Space Access Neutron Spectrometer (4SEASONS) and Elucidation of the Mechanism of Oxide High- Superconductivity" has started in 2005 (repr. by M. Arai). It is supported by MEXT, Grant-in-Aid for Specially Promoted Research and is going to last until fiscal 2009. The goal of the project is to elucidate the mechanism of oxide high- superconductivity by neutron scattering technique. For this purpose, we will develop an inelastic neutron scattering instrument 4SEASONS (4d SpacE AccesS neutrON Spectrometer) for the spallation neutron source in Japan Proton Accelerator Research Complex (J-PARC). The instrument will have 100 times higher performance than existing world-class instruments, and will enable detailed observation of anomalous magnetic excitations and phonons in a four-dimensional momentum-energy space. This report summarizes the progress in the research project in fiscal 2007.
Ga in unconventional superconductor PuRhGaSakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.50 - 52, 2006/08
Very recently, we have succeeded in NMR/NQR measurements for PuRhGa. PuRhGa is a superconductor with 
9 K, which is isomorphic to PuCoGa with the higher =18 K. We have reported that PuRhGa is an unconventional superconductor with an anisotropic gap, through the measurement of NQR spin-lattice relaxation rate , while PuCoGa is also reported to be such an anisotropic superconductor. The Knight shift 
and of NMR under applied field for the normal state of PuRhGa suggest an anisotropic feature of hyperfine and/or spin fluctuation in this system. We will outline the superconducting state and report the nature of the normal state based on the basis of and 
results. The difference between PuRhGa and PuCoGa will be also discussed.
Haga, Yoshinori; Aoki, Dai*; Yamagami, Hiroshi*; Matsuda, Tatsuma; Nakajima, Kunihisa; Arai, Yasuo; Yamamoto, Etsuji; Nakamura, Akio; Homma, Yoshiya*; Shiokawa, Yoshinobu*; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.4 - 9, 2006/08
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)The discovery of the high-temperature in PuCoGa and PuRhGa promoted us to extend our research to other actinide compounds. We recently succeeded in growing single crystals of PuRhGa and performed magnetic measurements and NMR study both in the normal and superconducting states in collaboration with Tohoku university. The magnetic susceptibility consists of Curie-Weiss and temperature-independent terms where the former corresponds to the paramagnetic effective moment close to the 5
configuration. On the other hand, the superconducting upper critical field is anisotropic. It is explained by the anisotropic mass model with an effective mass ratio of 4, indicating the presence of quasi-two-dimensional Fermi surfaces. These characteristics are reminiscent of those observed in CeCoIn.
Haga, Yoshinori; Aoki, Dai*; Yamagami, Hiroshi; Matsuda, Tatsuma; Nakajima, Kunihisa; Arai, Yasuo; Yamamoto, Etsuji; Nakamura, Akio; Homma, Yoshiya*; Shiokawa, Yoshinobu*; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.4 - 9, 2006/08
Single crystals of plutonium compounds PuRhGa and PuIn are successfully grown. For PuRhGa, anisotropy of the superconducting upper critical field was found and analyzed by the anisotropic mass model, consistent with quasi-two-dimensional electronic states predicted by band calculations. On the other hand, the de Haas-van Alphen oscillation was observed in PuIn. By comparing with the band calculations, it is concluded that 5
electrons are itinerant in PuIn.
