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Kondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
Times Cited Count:5 Percentile:92.64(Multidisciplinary Sciences)no abstracts in English
Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.
Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08
Times Cited Count:2 Percentile:68.16(Astronomy & Astrophysics)Detailed -ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.
Kubo, Kotaro; Fujiwara, Keita*; Tanaka, Yoichi; Hakuta, Yuto*; Arake, Daisuke*; Uchiyama, Tomoaki*; Muramatsu, Ken*
Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 8 Pages, 2022/08
After the Fukushima Daiichi Nuclear Power Plant accident, the importance of conducting probabilistic risk assessments (PRAs) of external events, especially seismic activities and tsunamis, was recognized. The Japan Atomic Energy Agency has been developing a computational methodology for seismic PRA, called the direct quantification of fault tree using Monte Carlo simulation (DQFM). When appropriate correlation matrices are available for seismic responses and capacities of components, the DQFM makes it possible to consider the effect of correlated failures of components connected through AND and/or OR gates in fault trees, which is practically difficult when methods using analytical solutions or multidimensional numerical integrations are used to obtain minimal cut set probabilities. The usefulness of DQFM has already been demonstrated. Nevertheless, a reduction of the computational time of DQFM would allow the large number of analyses required in PRAs conducted by regulators and/or operators. We; therefore, performed scoping calculations using three different approaches, namely quasi-Monte Carlo sampling, importance sampling, and parallel computing, to improve calculation efficiency. Quasi-Monte Carlo sampling, importance sampling, and parallel computing were applied when calculating the conditional core damage probability of a simplified PRA model of a pressurized water reactor, using the DQFM method. The results indicated that the quasi-Monte Carlo sampling works well at assumed medium and high ground motion levels, importance sampling is suitable for assumed low ground motion level, and that parallel computing enables practical uncertainty and importance analysis. The combined implementation of these improvements in a PRA code is expected to provide a significant acceleration of computation and offers the prospect of practical use of DQFM in risk-informed decision-making.
Yamaguchi, Akiko; Nagata, Kojiro*; Kobayashi, Keita; Tanaka, Kazuya; Kobayashi, Toru; Tanida, Hajime; Shimojo, Kojiro; Sekiguchi, Tetsuhiro; Kaneta, Yui; Matsuda, Shohei; et al.
iScience (Internet), 25(8), p.104763_1 - 104763_12, 2022/08
Times Cited Count:9 Percentile:68.46(Multidisciplinary Sciences)no abstracts in English
Yamaguchi, Akiko; Nagata, Kojiro*; Tanaka, Kazuya; Kobayashi, Keita; Kobayashi, Toru; Shimojo, Kojiro; Tanida, Hajime; Sekiguchi, Tetsuhiro; Kaneta, Yui; Matsuda, Shohei; et al.
Hosha Kagaku, (45), p.28 - 30, 2022/03
no abstracts in English
Komura, Keitaro*; Kaneda, Heitaro*; Tanaka, Tomoki*; Kojima, Satoru*; Inoue, Tsutomu*; Nishio, Tomohiro
Geomorphology, 365, p.107214_1 - 107214_22, 2020/09
Times Cited Count:1 Percentile:9.84(Geography, Physical)On the basis of pit excavations and sediment cores at an off-fault deep-seated gravitational slope deformation (DGSD) site and a trench excavation across the active Neodani fault at a nearby site, we examined the records of DGSD and surface-rupturing paleoearthquakes of the Neodani fault. We found the four most recent DGSD events and the four most recent surface-rupturing earthquakes, respectively and conclude that the ages of events are overlapped each other. We infer that static crustal strain from repeated seismogenic faulting plays an important role in the occurrence of DGSD events, at least in the immediate vicinity of active faults, although coseismic severe shaking would have at least some effect on them. Our case study suggests that off-fault DGSDs can be used to reconstruct or refine the paleoseismic history of a nearby active fault.
Myagmarjav, O.; Iwatsuki, Jin; Tanaka, Nobuyuki; Noguchi, Hiroki; Kamiji, Yu; Ioka, Ikuo; Kubo, Shinji; Nomura, Mikihiro*; Yamaki, Tetsuya*; Sawada, Shinichi*; et al.
International Journal of Hydrogen Energy, 44(35), p.19141 - 19152, 2019/07
Times Cited Count:16 Percentile:49.6(Chemistry, Physical)Hirose, Kentaro; Nishio, Katsuhisa; Tanaka, Shoya*; Lguillon, R.*; Makii, Hiroyuki; Nishinaka, Ichiro*; Orlandi, R.; Tsukada, Kazuaki; Smallcombe, J.*; Vermeulen, M. J.; et al.
Physical Review Letters, 119(22), p.222501_1 - 222501_6, 2017/12
Times Cited Count:50 Percentile:91.08(Physics, Multidisciplinary)Fission-fragment mass distributions were measured for U, Np and Pu populated in the excitation-energy range from 10 to 60 MeV by multi-nucleon transfer channels in the reaction O + U at the JAEA tandem facility. Among them, the data for U and Np were observed for the first time. It was found that the mass distributions for all the studied nuclides maintain a double-humped shape up to the highest measured energy in contrast to expectations of predominantly symmetric fission due to the washing out of nuclear shell effects. From a comparison with the dynamical calculation based on the fluctuation-dissipation model, this behavior of the mass distributions was unambiguously attributed to the effect of multi-chance fission.
Ito, Saya*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Kawamura, Seiko; Nakajima, Kenji; Ito, Shinichi*; Kuwahara, Keitaro*; Kakurai, Kazuhisa*
Nature Communications (Internet), 8, p.235_1 - 235_6, 2017/08
Times Cited Count:76 Percentile:93.89(Multidisciplinary Sciences)Kamiya, Junichiro; Hikichi, Yusuke; Kinsho, Michikazu; Ogiwara, Norio; Fukuda, Mitsuhiro*; Hamatani, Noriaki*; Hatanaka, Kichiji*; Kamakura, Keita*; Takahisa, Keiji*
Journal of Vacuum Science and Technology A, 33(3), p.031605_1 - 031605_8, 2015/05
Times Cited Count:5 Percentile:22.94(Materials Science, Coatings & Films)For the vacuum systems of high-intensity beam accelerators, low radioactivation materials with good vacuum characteristics and high mechanical strength are required. The titanium alloy Ti-6Al-4V was investigated as a potential low activation vacuum material with high mechanical strength for the fabrication of vacuum components, particularly the flanges of beam pipes, in the J-PARC 3 GeV synchrotron. The dose rate of Ti-6Al-4V when irradiated by a 400 MeV proton was observed to decrease more rapidly than that of stainless steel. Furthermore, the generated radioactive isotopes were nuclides with relatively short half-lives. The outgassing rate of Ti-6Al-4V was the same as the typical value for stainless steel. Additionally, the hydrogen concentration in bulk Ti-6Al-4V was reduced to approximately 1 ppm by vacuum firing. These results indicate that Ti-6Al-4V is a good candidate for use as a low activation vacuum material with high mechanical strength.
Yamashita, Riyo; Hama, Katsuhiro; Takeuchi, Ryuji; Morikawa, Keita*; Hosoya, Shinichi*; Nakamura, Toshiaki*; Tanaka, Yumiko*
JAEA-Technology 2014-029, 118 Pages, 2014/09
This study is to gain a better understanding of mass transfer phenomena in the geological environment as well as to develop technologies for: measurement of the solute transport parameters, model construction, numerical analysis and validation of all those technologies based on the existing information. As part of solute transport study, laboratory experiments were planned to understand the influence of the geological characteristics of fracture on the solute transport parameters, also understand the differences in test results by the different sizes of the samples used for an experiment, and moreover to validate the parameters obtained by numerical analysis.
Kamiya, Junichiro; Ogiwara, Norio; Kinsho, Michikazu; Kamakura, Keita*; Hamatani, Noriaki*; Hatanaka, Kichiji*; Fukuda, Mitsuhiro*; Takahisa, Keiji*
Journal of the Vacuum Society of Japan, 56(5), p.167 - 171, 2013/05
no abstracts in English
Morita, 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.
Tanaka, Teruya*; Sato, Satoshi; Kondo, Keitaro; Ochiai, Kentaro; Murata, Isao*; Takakura, Kosuke; Sato, Fuminobu*; Kada, Wataru*; Iida, Toshiyuki*; Konno, Chikara; et al.
Fusion Science and Technology, 60(2), p.681 - 686, 2011/08
Times Cited Count:1 Percentile:10.73(Nuclear Science & Technology)Irradiation experiments of 14 MeV neutrons have been performed on a Li block assembly of 46 51 51 cm with a 5 cm thick V-alloy layer inside to examine the accuracy of neutronics calculations for the Li/V-alloy blanket design. Foils of Nb, Ni, In and Au for reaction rate measurements of Nb(n,2n)Nb, Ni(n,p)Co, In(n,n')In, Au(n,)Au reactions and Li enriched (Li: 95.5%) and Li enriched (Li: 99.9%) LiCO pellets for tritium production rate measurements were installed in the assembly. Results of the measurements were compared with those of calculations with MCNP5, JENDL-3.3 and JENDL/D-99. The comparisons for the reaction rates in the Nb, Ni and In foils indicate that measurements and calculations of the fast neutron transport are consistent almost within 10%. In the comparison for the reaction rates in the Au foils, the underestimation of 15% was found at a surface of the V-alloy layer. There is a possibility that this is due to the elastic scattering cross section of V around 4 keV as previously reported. The comparisons for tritium production rates in the Li enriched and Li enriched LiCO pellets indicate that calculated rates were larger than results of the measurements by 2-8% and 1-4%, respectively.
Sato, Satoshi; Takakura, Kosuke; Ochiai, Kentaro; Kondo, Keitaro; Tatebe, Yosuke; Onishi, Seiki; Wada, Masayuki*; Kutsukake, Chuzo; Tanaka, Shigeru; Abe, Yuichi; et al.
Fusion Science and Technology, 56(1), p.227 - 231, 2009/07
Times Cited Count:1 Percentile:10.22(Nuclear Science & Technology)Previously DT neutronics experiments were performed by using partial blanket mockups for Japanese ITER test blanket module at JAEA FNS, and tritium production rates (TPR) inside blanket mockups were measured in details. The calculation with the nuclear data library FENDL-2.1 and Monte Carlo code MCNP4C agreed well with most of the measured TPRs within uncertainty of 10%. On the other hand, overestimations were found for the TPR in the experiment with a reflector and the TPR around the boundary between the rear part of the breeder layer and the beryllium layer by more than 10%. In order to confirm this concern, we measured reaction rate distribution in the partial blanket mockups with DT neutrons with two solid breeder blanket partial mockups, (Be/LiTiO/Be, SS316/LiTiO/SS316). Experiments were performed with and without a neutron source reflector. In order to measure reaction rate distributions, the activation foil method was applied using Nb and Au foils in this study. Experimental analyses were performed by MCNP4C with FENDL-2.1. Calculation results to experimental ones (C/Es) on the Au reaction rate with a reflector were larger than those without one. Detailed results are presented in this conference.
Saiki, Yumi*; Takata, Kinuko*; Uchimura, Yosuke*; Hirashima, Keita*; Nakahara, Takao*; Hase, Yoshihiro; Yokota, Yuichiro; Tanaka, Atsushi
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 70, 2008/03
no abstracts in English
Uchimura, Yosuke*; Takata, Kinuko*; Saiki, Yumi*; Hirashima, Keita*; Nakahara, Takao*; Hase, Yoshihiro; Yokota, Yuichiro; Tanaka, Atsushi
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 80, 2007/02
no abstracts in English
Toida, Masaru*; Suyama, Yasuhiro*; Inaba, Takeshi*; Sasakura, Takeshi*; Atsumi, Hiroyuki*; Tanaka, Toshiyuki*; Kobayashi, Ichizo*; Iwano, Keita*; Furuichi, Mitsuaki*
JNC TJ7400 2004-017, 521 Pages, 2004/02
"Geoscientific research" at Tono is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important themes are to establish a methodology for analyzing uncertainties in heterogeneous geological environment and to develop investigation techniques for reducing the uncertainties efficiently. The current study proposes a new approach where all the possible options in the models and data-sets that cannot be excluded in the light of the evidence available is identified. This approach enables uncertainties associated with the understanding at a given stage of the site characterization to be made explicitly using an uncertainty analysis technique based on Fuzzy geostatistics. This, in turn, supports the design of the following investigation stage to reduce the uncertainties efficiently. In this report the technique has been tested through geological modelling and groundwater analysis with Tono area case based on current knouledge, to demonstrate its applicability. This report summarizes as follows: (1)It is possible to quantify the uncertainties with Tono area case based on current knouledge using the technique. (2)Based on sensitivity analyses, it is possible to support designs of the following investigation stage to reduce the uncertainties efficiently. (3)The methodology of the technique has been developed with Tono area case. (4)The above could evaluate its applicability and propose further issues for synthesis of the methodology.
Uchimura, Yosuke*; Takata, Kinuko*; Saiki, Yumi*; Hirashima, Keita*; Nakahara, Takao*; Hase, Yoshihiro; Yokota, Yuichiro; Tanaka, Atsushi
no journal, ,
no abstracts in English
Tanaka, Teruya*; Muroga, Takeo*; Sato, Satoshi; Ochiai, Kentaro; Takakura, Kosuke; Kondo, Keitaro; Konno, Chikara; Kada, Wataru*; Sato, Fuminobu*; Murata, Isao*; et al.
no journal, ,
no abstracts in English