Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Zn
Y
alloy using X-ray photoelectron spectroscopyMiyazaki, Hidetoshi*; Akatsuka, Tatsuyoshi*; Kimura, Koji*; Egusa, Daisuke*; Sato, Yohei*; Itakura, Mitsuhiro; Takagi, Yasumasa*; Yasui, Akira*; Ozawa, Kenichi*; Mase, Kazuhiko*; et al.
Materials Transactions, 64(6), p.1194 - 1198, 2023/06
Times Cited Count：1 Percentile：54.26(Materials Science, Multidisciplinary)We investigated the electronic structure of the MgZnY alloy using hard and soft X-ray photoemission spectroscopy and electronic band structure calculations to understand the mechanism of the phase stability of this material. Electronic structure of the MgZnY alloy showed a semi-metallic electronic structure with a pseudo-gap at the Fermi level. The observed electronic structure of the MgZnY alloy suggests that the presence of a pseudogap structure is responsible for phase stability.
Kato, Masato; Machida, Masahiko; Hirooka, Shun; Nakamichi, Shinya; Ikusawa, Yoshihisa; Nakamura, Hiroki; Kobayashi, Keita; Ozawa, Takayuki; Maeda, Koji; Sasaki, Shinji; et al.
Materials Science and Fuel Technologies of Uranium and Plutonium mixed Oxide, 171 Pages, 2022/10
Innovative and advanced nuclear reactors using plutonium fuel has been developed in each country. In order to develop a new nuclear fuel, irradiation tests are indispensable, and it is necessary to demonstrate the performance and safety of nuclear fuels. If we can develop a technology that accurately simulates irradiation behavior as a technology that complements the irradiation test, the cost, time, and labor involved in nuclear fuel research and development will be greatly reduced. And safety and reliability can be significantly improved through simulation of nuclear fuel irradiation behavior. In order to evaluate the performance of nuclear fuel, it is necessary to know the physical and chemical properties of the fuel at high temperatures. And it is indispensable to develop a behavior model that describes various phenomena that occur during irradiation. In previous research and development, empirical methods with fitting parameters have been used in many parts of model development. However, empirical techniques can give very different results in areas where there is no data. Therefore, the purpose of this study is to construct a scientific descriptive model that can extrapolate the basic characteristics of fuel to the composition and temperature, and to develop an irradiation behavior analysis code to which the model is applied.
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Watanabe, Takashi*; Ozawa, Osamu*; Takeuchi, Tomoaki
Denki Gakkai-Shi, 138(8), p.529 - 534, 2018/08
no abstracts in English
= 100 with a multireflection time-of-flight mass spectrographIto, Yuta*; Schury, P.*; Wada, Michiharu*; Arai, Fumiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Ishizawa, Satoshi*; Kaji, Daiya*; Kimura, Sota*; Koura, Hiroyuki; et al.
Physical Review Letters, 120(15), p.152501_1 - 152501_6, 2018/04
Times Cited Count：60 Percentile：93.36(Physics, Multidisciplinary)Masses of 
Es, 
Fm and the transfermium nuclei 
Md, and 
No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed 
neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of Es and 
Md were measured for the first time. Using the masses of 
Md as anchor points for 
decay chains, the masses of heavier nuclei, up to 
Bh and 
Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter 
derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed neutron shell closure for Md and Lr.
I in the contaminated water and tree samples at the Fukushima Daiichi Nuclear Power StationShimada, Asako; Ozawa, Mayumi; Kameo, Yutaka; Yasumatsu, Takuyo*; Nebashi, Koji*; Niiyama, Takuya; Seki, Shuhei; Kajio, Masatoshi; Takahashi, Kuniaki
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.311 - 317, 2015/00
no abstracts in English
Ikusawa, Yoshihisa; Ozawa, Takayuki; Hirooka, Shun; Maeda, Koji; Kato, Masato; Maeda, Seiichiro
Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 6 Pages, 2014/07
In order to develop MA contained MOX (MA-MOX) fuel design method, the analysis models to predict irradiation behavior of MA-MOX fuel have to be developed and the accuracy of irradiation behavior analysis code should be evaluated with the result of post-irradiation examinations (PIEs) for MA-MOX fuels. In this study, we developed the computer module "TRANSIT" to compute thermal properties of MA-MOX fuel. TRANSIT can give thermal conductivity, melting temperature and vapor pressures of MA-MOX. By using this module, we improved the thermal behavior analysis code "DIRAD" and developed DIRAD-TRANSIT code system to compute the irradiation behavior of MA-MOX fuel. This system was verified with the results of PIEs for the conventional MOX fuels and the MA-MOX fuels irradiated in the experimental fast reactor "JOYO". As the result of the verification, it can be mentioned that the DIRAD-TRANSIT system would precisely predict the fuel thermal behavior, i.e. fuel temperature and fuel restructuring, for oxide fuels containing several percent minor actinides.
Schury, P. H.*; Wada, Michiharu*; Ito, Yuta*; Naimi, S.*; Sonoda, Tetsu*; Mita, Koki*; Takamine, Aiko*; Okada, Kunihiro*; Wollnik, H.*; Chon, S.*; et al.
Nuclear Instruments and Methods in Physics Research B, 317(Part B), p.537 - 543, 2013/12
Times Cited Count：28 Percentile：89.14(Instruments & Instrumentation)A multi-reflection time-of-flight (MRTOF) mass spectrograph has been implemented at RIKEN to provide high-precision mass measurements of very short-lived nuclei. Of particular interest are mass measurements of r-process nuclei and trans-uranium nuclei. In such nuclei, the MRTOF can perform on par with or better than traditional Penning trap systems. We demonstrate that the MRTOF-MS is capable of accurately attaining relative mass precision of 
m/m 
10
and describe it's utility with heavy, short-lived nuclei.
113 of the 113th elementMorita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sumita, Takayuki*; Wakabayashi, Yasuo*; Yoneda, Akira*; Tanaka, Kengo*; et al.
Journal of the Physical Society of Japan, 81(10), p.103201_1 - 103201_4, 2012/10
Times Cited Count：167 Percentile：97.27(Physics, Multidisciplinary)An isotope of the 113th element, 113, was produced in a nuclear reaction with a 
Zn beam on a 
Bi target. We observed six consecutive decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector, in extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of 
Db and 
Lr both in decay energies and decay times. This indicates that the present decay chain consisted of 113, 
Rg (Z = 111), 
Mt (Z = 109), Bh (Z = 107), Db (Z = 105), and Lr (Z = 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads the unambiguous production and identification of the isotope 113, of the 113th element.
P
O
Hase, Masashi*; D
nni, A.*; Ozawa, Kiyoshi*; Kitazawa, Hideaki*; Sakai, Osamu*; Pomjakushin, V. Y.*; Keller, L.*; Kaneko, Koji; Metoki, Naoto; Kakurai, Kazuhisa; et al.
Journal of Physics; Conference Series, 340, p.012066_1 - 012066_7, 2012/00
Times Cited Count：1 Percentile：44.95(Physics, Condensed Matter)We determined the magnetic structure below 
K of the spin-5/2 antiferromagnetic (AF) trimer substance SrMnPO using neutron powder diffraction experiments. The incommensurate propagation vector is expressed as [0, 
, 0], due to competition between the nearest-neighbor and next-nearest-neighbor interactions in trimerized chains. The value of is 0.316 to 0.331, changing rapidly at 
K. We confirmed that the intra-trimer 
interaction is AF. The magnetic excitation peaks were obsereved at 0.46, 0.68, and 1.02 meV. The weak Q dependence indicates the discrete energy levels, which do not contradict the AF trimer model with the intra-trimer interaction value of 0.29 meV (3.4 K).
Toyoshima, Hiroaki*; Hiraga, Kenta*; Ono, Shinya*; Tanaka, Masatoshi*; Ozawa, Kenichi*; Mase, Kazuhiko*; Hirao, Norie; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Baba, Yuji
Photon Factory Activity Report 2011, Part B, P. 102, 2012/00
The knowledge of the interaction between organic molecules and semiconductor surfaces plays an important role in adapting organic semiconductors into the semiconductor technology. In the present study, the process of -sexithiophene (-6T) thin layer formation on passivated silicon (Si) surfaces has been investigated in-situ by means of PES, angle-depended NEXAFS (near-edge X-ray absorption fine-structure), SDRS, and RDS. For water-adsorbed Si(001), it was found that the majority of -6T molecules are standing on the substrate. Above 3 nm, most of molecules are standing and constitute well ordered islands or films. For ethylene adsorbed Si(001) on the contrary, some of -6T molecules are flat-lying, resulting in less prominent orientation. Thus, the orientation of molecules depends on the method of passivation, which opens the possibility of controlling the molecular orientation by the surface modification.
Koyama, Shinichi; Suzuki, Tatsuya*; Ozawa, Masaki*; Kurosawa, Kiyoko*; Fujita, Reiko*; Mimura, Hitoshi*; Okada, Ken*; Morita, Yasuji; Fujii, Yasuhiko*
Procedia Chemistry, 7, p.222 - 230, 2012/00
Times Cited Count：2 Percentile：71.08(Chemistry, Analytical)Adv.-ORIENT cycle strategy has been proposed as a basic concept for trinitarian research on separation, transmutation and utilization of nuclides and elements based on FBR fuel cycle. Validation of principal separation method and related safety research were performed from 2006 through 2011 as Phase I program. First, more than 90% of Cs could be recovered from the actual spent fuel [IXC(I) step]. The next is the adsorption of the platinum group metals (PGM), lanthanides, Am and Cm were separated by using a tertiary pyridine-type resin (TPR) as ion exchange steps [IXC(II, III, IV) steps]. The separated PGM metals will be supplied to the electrochemical extraction [CEE step]. As experiment for safety issues, Hastelloy-B at RT and Ta at 90
C were confirmed their anti-corrosive in highly concentrated HCl media. Thermo-chemical stability for TPR was verified. Issues to be solved for next phase based on the final results of phase I program.
Hs and 
HsSato, Nozomi; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Kaji, Daiya*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozeki, Kazutaka*; Sumita, Takayuki*; Yoneda, Akira*; et al.
Journal of the Physical Society of Japan, 80(9), p.094201_1 - 094201_7, 2011/09
Times Cited Count：15 Percentile：65.33(Physics, Multidisciplinary)Decay properties of Hs and Hs produced in the 
Pb(
Fe, 
) [
=1, 2] reactions were studied using a gas-filled recoil ion separator at the linear accelerator facility of RIKEN. A total of 6 decay chains were assigned to Hs. Cross sections for the Hs production in the 
Pb(Fe,
) and 
Pb(Fe,
) reactions were measured to be 
pb and 
pb, respectively. The isotope Hs decayed with a half-life of 
ms by -particle emission and spontaneous fission. The -particle energy of Hs was observed at 10.61
0.04 and 10.800.08 MeV. The spontaneous fission branch of Hs was found to be 
.
Kato, Masato; Maeda, Koji; Ozawa, Takayuki; Kashimura, Motoaki; Kihara, Yoshiyuki
Journal of Nuclear Science and Technology, 48(4), p.646 - 653, 2011/04
Physical properties and irradiation behavior of minor actinide-bearing MOX were evaluated for the development of advanced fast reactor fuels. The physical properties of the fuels were described as functions of minor actinide content and oxygen-to-metal (
/
) ratio, and the effect of minor actinide addition into MOX on those properties was found to be negligibly small. The irradiation tests of fuel pellets having / ratios of 1.98 or 1.96 were carried out at high linear heat rate of about 430W/cm. The redistribution of actinide element and oxygen were analyzed by using the evaluated properties, and maximum temperatures of the pellets were estimated. The maximum temperature of the pellets of /=1.96 was estimated to reach 2680K which was 130K higher than that of /=1.98 pellets. The maximum temperature of the pellet was lower as compared with its melting temperature of higher than 3000K. In the results of post-irradiation examination, no trace of melting was observed.
Bh and Db produced in the 
Cm + 
Na reactionMorita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi*; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.
Journal of the Physical Society of Japan, 78(6), p.064201_1 - 064201_6, 2009/06
Times Cited Count：30 Percentile：78.34(Physics, Multidisciplinary)Decay properties of an isotope Bh and its daughter nucleus Db produced by the Cm(Na,5) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. Bh was clearly identified from the correlation of the known nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.
HsKaji, Daiya*; Morimoto, Koji*; Sato, Nozomi*; Ichikawa, Takatoshi*; Ideguchi, Eiji*; Ozeki, Kazutaka*; Haba, Hiromitsu*; Koura, Hiroyuki; Kudo, Yuki*; Ozawa, Akira*; et al.
Journal of the Physical Society of Japan, 78(3), p.035003_1 - 035003_2, 2009/03
A new hassium isotopes Hs is directly produced for the first time. The experiment was performed at the linear accelerator (RILAC) facility in RIKEN (the Institute of Physical and Chemical Research) from Jun. 19 to 25. In the 25-h irradiation of Fe on 
Pb and 46-h irradiation of 
Fe on Pb, 8 decay chains and 1 decay chain, respectively, were observed. All decay chains were assigned to subsequent decays from Hs. The half-life of Hs is 0.60
ms. In this experiment, the total beam dose was 
ions for Fe and 
ions for Fe. The production cross section corresponding to 8 decay events and 1 decay chain was deduced to be 21
pb and 1.6
pb by assuming that the transmission of the system is 80%.
HsKaji, Daiya*; Morimoto, Koji*; Sato, Nozomi*; Ichikawa, Takatoshi*; Ideguchi, Eiji*; Ozeki, Kazutaka*; Haba, Hiromitsu*; Koura, Hiroyuki; Kudo, Yuki*; Ozawa, Akira*; et al.
Journal of the Physical Society of Japan, 78(3), p.035003_1 - 035003_2, 2009/03
Times Cited Count：3 Percentile：26.3(Physics, Multidisciplinary)A new neutron deficient hassium (=108) isotope of Hs was identified via two different reactions of Pb(Fe,n) and Pb(Fe,n) by using a gas-filled recoil separator GARIS at June 2008. During the 25-h irradiation of Pb with the Fe beam and 46-h irradiation of Pb with the Fe beam, 8 decay chains and 1 decay chain, respectively, have been observed. The half-life of Hs is 0.60
ms. In this experiment, the total beam doses of the Fe and Fe was 4.1
10
ions and 6.210 ions, respectively. The production cross sections corresponding to the 8 decay chains and 1 decay chain have been deduced to be 21 pb and 1.6 pb by assuming the transmission of the system to be 80%.
Hs, 
Sg, and 
RfSato, Nozomi*; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Ideguchi, Eiji*; Kaji, Daiya*; Koura, Hiroyuki; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozawa, Akira*; et al.
RIKEN Accelerator Progress Report, Vol.42, P. 16, 2009/00
New Decay Properties of Hs and its -decay daughter nuclei were studied by using reactions of Pb(Fe,2n) and Pb(Fe,n) by using a gas-filled recoil ion separator, GARIS at RIKEN. We observed three correlated events in irradiation of Fe on Pb, and eight events in irradiation of Fe on Pb. A half-life was deduced to be 0.90
. We assigned these eleven events to be the decays of Hs. We found different decay-chain events of Hs from a previous report. One is a long-lived -decay of Sg with 180
ms of half-life. Another is a long-lived -decay of Rf with 10.4
s of half-life. For Sg and Rf, the decay of such a long-lived state have not been reported. These are the first observations of isomerism in Sg and Rf.
113Morimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kudo, Hisaaki*; et al.
RIKEN Accelerator Progress Report, Vol.42, P. 15, 2009/00
In 2003-2007, we had performed an experiment to synthesize an element 113 by a Bi
Zn reaction using a gas-filled recoil ion separator (GARIS) at RIKEN Nishina-Center. In a total of 241 days of net irradiation time experiment, two decay chains were observed and assigned from an isotope 113. The cross section of the Bi(Zn,n)113 reaction was determined to be 31
fb at that time. In order to increase the statistics of the decay property, we continued to produce more decay chains. The experiment was carried out from January 7 to March 31, 2008. The experimental conditions were identical to those used in the previous experiment. Zn ion beam of 353 MeV was extracted from RILAC. The net irradiation time was 83 days and the total dose of Zn was 2.28
. In the present expriment any candidate of 113 was not observed. Then combining the results of the present and previous experiments, the production cross section of 113 was determined to be 22
fb.
112 by Pb + Zn reactionMorita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kudo, Hisaaki*; et al.
Journal of the Physical Society of Japan, 76(4), p.043201_1 - 043201_5, 2007/04
Times Cited Count：150 Percentile：95.98(Physics, Multidisciplinary)The production and decay of 112 has been investigated using a gas-filled recoil ion separator in irradiations of Pb targets with Zn beam at 349.5 MeV. We have observed two -decay chains that can be assigned to subsequent decays from 112 produced in the 208 Pb(Zn,n) reaction. After emitting four consecutive -particles, the both chains ended by spontaneous fission decays of Rf and decay energies and decay times of the both chains obtained in the present work agree well with those reported by a group at Gesellschaft f
r Schwerionenforschung (GSI), Germany. The present result gives the first clear confirmation of the discovery of 112 and its -decay products 
Ds reported previously.
