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Horii, Yuta; Hirooka, Shun; Uno, Hiroki*; Ogasawara, Masahiro*; Tamura, Tetsuya*; Yamada, Tadahisa*; Furusawa, Naoya*; Murakami, Tatsutoshi; Kato, Masato
Journal of Nuclear Materials, 588, p.154799_1 - 154799_20, 2024/01
Times Cited Count:1 Percentile:72.91(Materials Science, Multidisciplinary)The thermal conductivities of near-stoichiometric (U,Pu,Am)O doped with NdO/SmO, which is major fission product (FP) generated by a uranium-plutonium mixed oxides (MOX) fuel irradiation, as simulated fission products are evaluated at 1073-1673 K. The thermal conductivities are calculated from the thermal diffusivities that are measured using the laser flash method. To evaluate the thermal conductivity from a homogeneity viewpoint of Nd/Sm cations in MOX, the specimens with different homogeneity of Nd/Sm are prepared using two kinds of powder made by ball-mill and fusion methods. A homogeneous Nd/Sm distribution decreases the thermal conductivity of MOX with increasing Nd/Sm content, whereas heterogeneous Nd/Sm has no influence. The effect of Nd/Sm on the thermal conductivity is studied using the classical phonon transport model (A+BT). The dependences of the coefficients A and B on the Nd/Sm content (C and C, respectively) are evaluated as: A(mK/W)=1.70 10 + 0.93C + 1.20C, B(m/W)=2.39 10.
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.
Tamatsukuri, Hiromu; Fukui, Keiga*; Iimura, Soshi*; Honda, Takashi*; Tada, Tomofumi*; Murakami, Yoichi*; Yamaura, Junichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Yamada, Takeshi*; et al.
Physical Review B, 107(18), p.184114_1 - 184114_8, 2023/05
Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)Tamatsukuri, Hiromu; Hasegawa, Takumi*; Sagayama, Hajime*; Mizumaki, Masaichiro*; Murakami, Yoichi*; Kajitani, Joe*; Higashinaka, Ryuji*; Matsuda, Tatsuma*; Aoki, Yuji*; Tsutsui, Satoshi*
Physical Review B, 107(2), p.024303_1 - 024303_8, 2023/01
Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)Xu, S.*; Odaira, Takumi*; Sato, Shunsuke*; Xu, X.*; Omori, Toshihiro*; Harjo, S.; Kawasaki, Takuro; Seiner, H.*; Zoubkov, K.*; Murakami, Yasukazu*; et al.
Nature Communications (Internet), 13, p.5307_1 - 5307_8, 2022/09
Times Cited Count:8 Percentile:66.14(Multidisciplinary Sciences)Takeuchi, Ryuji; Onoe, Hironori; Murakami, Hiroaki; Watanabe, Yusuke; Mikake, Shinichiro; Ikeda, Koki; Iyatomi, Yosuke; Nishio, Kazuhisa*; Sasao, Eiji
JAEA-Review 2021-003, 63 Pages, 2021/06
The Mizunami Underground Research Laboratory (MIU) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of geological disposal technologies through investigations of the deep geological environment in the crystalline rock (granite) at Mizunami City, Gifu Prefecture, central Japan. On the occasion of JAEA reformation in FY2014, JAEA identified three remaining important issues on the geoscientific research program based on the synthesized latest results of research and development (R&D): "Development of countermeasure technologies for reducing groundwater inflow", "Development of modeling technologies for mass transport" and "Development of drift backfilling technologies". At the MIU, the R&D are being pursued with a focus on the remaining important issues from FY2015, and satisfactory results have been achieved. Based on this situation, the R&D on the MIU Project were completed at the end of FY2019. In this report, the results of R&D and construction activities of the MIU Project in FY2019 are summarized.
Tamatsukuri, Hiromu; Murakami, Yoichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Matsuura, Masato*; Kawakita, Yukinobu; Matsuishi, Satoru*; Washio, Yasuhito*; Inoshita, Takeshi*; Hamada, Noriaki*; et al.
Physical Review B, 102(22), p.224406_1 - 224406_5, 2020/12
Times Cited Count:8 Percentile:49.08(Materials Science, Multidisciplinary)Yamaura, Junichi*; Hiraka, Haruhiro*; Iimura, Soshi*; Muraba, Yoshinori*; Bang, J.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Honda, Takashi*; Hiraishi, Masatoshi*; et al.
Physical Review B, 99(22), p.220505_1 - 220505_6, 2019/06
Times Cited Count:3 Percentile:16.31(Materials Science, Multidisciplinary)Inelastic neutron scattering was performed for an iron-based superconductor, where most of D (deuterium) replaces oxygen, while a tiny amount goes into interstitial sites. By first-principle calculation, we characterize the interstitial sites for D (and for H slightly mixed) with four equivalent potential minima. Below the superconducting transition temperature Tc = 26 K, new excitations emerge in the range 5-15 meV, while they are absent in the reference system LaFeAsOF. The strong excitations at 14.5 meV and 11.1 meV broaden rapidly around 15 K and 20 K, respectively, where each energy becomes comparable to twice of the superconducting gap. The strong excitations are ascribed to a quantum rattling, or a band motion of hydrogen, which arises only if the number of potential minima is larger than two.
Nishio, Kazuhisa*; Murakami, Hiroaki; Iyatomi, Yosuke; Hama, Katsuhiro
JAEA-Review 2018-037, 53 Pages, 2019/03
The Tono Geoscience Center (TGC) of Japan Atomic Energy Agency (JAEA) has been conducting geoscientific study in order to establish a scientific and technological basis for the geological disposal of HLW. Technical information of the result on the geoscientific study conducted at TGC is provided at the annual Information and Opinion Exchange Conference on Geoscientific Study of TGC for exchanging opinions among researchers and engineers from universities, research organizations and private companies. This document compiles the research presentations and posters of the conference in Mizunami on November 29, 2018.
Tamatsukuri, Hiromu*; Hiraka, Haruhiro*; Ikeuchi, Kazuhiko*; Iimura, Soshi*; Muraba, Yoshinori*; Nakamura, Mitsutaka; Sagayama, Hajime*; Yamaura, Junichi*; Murakami, Yoichi*; Kuramoto, Yoshio*; et al.
Physical Review B, 98(17), p.174415_1 - 174415_6, 2018/11
Times Cited Count:3 Percentile:15.56(Materials Science, Multidisciplinary)Magnetic excitations in a heavily electron-doped antiferromagnet, LaFeAsOD, have been investigated using powder inelastic neutron scattering. Unlike other parent compounds of the iron-based superconductors, the magnetic excitation gap in LaFeAsOD was not detected down to the lowest measured temperature of 4 K. This result can be understood as a result of quasi-isotropy within the ab plane, which is consistent with the band calculation result that the orbital plays the dominant role in the magnetism of LaFeAsOH. In addition, the intensities of the magnetic excitations in this phase are much stronger than those in nondoped LaFeAsO. Even in the paramagnetic phase, the magnetic excitation in LaFeAsOD persists. These results corroborate recent studies showing that the electron doping enhances the localized nature in this system.
Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Shintaku, Yohei*; Li, T.*; Murakami, Kazuya*; Kanomata, Kenichi*; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi; et al.
Journal of Nuclear Materials, 506, p.3 - 11, 2018/08
Times Cited Count:3 Percentile:30.05(Materials Science, Multidisciplinary)The mercury target vessel is designed as multi-walled structure with thin wall (min. 3 mm), and assembled by welding. In order to estimate the structural integrity of the vessel, it is important to measure the defects in welding accurately. For nondestructive tests of the welding, radiographic testing is applicable but it is difficult to detect for some defect shapes. Therefore it is effective to do ultrasonic testing together with it. Because ultrasonic methods prescribed in JIS inspect on the plate with more than 6 mm in thickness, these methods couldn't be applied as the inspection on the vessel with thin walls. In order to develop effective method, we carried out measurements using some testing method on samples with small defect whose size is specified. In the case of the latest phased array method, measured value agreed with actual size. It was found that this method was applicable to detect defects in the thin-walled structure for which accurate inspection was difficult so far.
Takeishi, Minoru; Shibamichi, Masaru; Malins, A.; Kurikami, Hiroshi; Murakami, Mitsuhiro*; Saegusa, Jun; Yoneya, Masayuki
Journal of Environmental Radioactivity, 177, p.1 - 12, 2017/10
By convention radiation measurements from vehicle-borne surveys are converted to the dose rate at 1 m above the ground in the absence of the vehicle. To improve the accuracy of the converted results from vehicle-borne surveys, we investigated combining measurements from two detectors mounted on the vehicle at different heights above the ground. A dual-detector setup was added to a JAEA monitoring car and compared against hand-held survey meter measurements in Fukushima Prefecture. The dose rates obtained by combining measurements from two detectors were within 20% of the hand-held reference measurements. The combined results from the two detectors were more accurate than those from either the roof-mounted detector, or the detector inside the vehicle, taken alone. When radiocesium is deficient on a road compared to the adjacent land, mounting detectors high on vehicles yields dose rates closer to the values adjacent to the road. We also investigated mounting heights for vehicle-borne detectors using Monte Carlo -ray simulations.
Saegusa, Jun; Yoda, Tomoyuki; Murakami, Mitsuhiro; Takeishi, Minoru
Kankyo Hoshano Josen Gakkai-Shi, 5(2), p.79 - 93, 2017/06
After the Fukushima Daiichi Nuclear Power Plant (NPP) accident in March 2011, environmental radiation monitoring works have been continuously conducted throughout the Fukushima prefecture of Japan. Five-year transitions of ambient dose rates at 15 locations 20-60 km away from the NPPs were precisely analyzed to investigate their chronological change. Measured dose rates were successfully fitted into a function consisting of a factor reflecting the physical decay of radiocesium and the other component such as the weathering effect. The ecological half-lives derived from the function ranged from 3 to 27 years (average 10 years). The radiation shielding effect by snow covering was also studied with the obtained functions. Due to the effect, dose rates were lowered by 15-50% by 20-cm-deep snow covering, and the ambient doses integrated over the five years were found to decrease by up to 7% compared to those without the snow covering that can be predicted from the fit function.
Frandsen, B. A.*; Liu, L.*; Cheung, S. C.*; Guguchia, Z.*; Khasanov, R.*; Morenzoni, E.*; Munsie, T. J. S.*; Hallas, A. M.*; Wilson, M. N.*; Cai, Y.*; et al.
Nature Communications (Internet), 7, p.12519_1 - 12519_8, 2016/08
Times Cited Count:33 Percentile:77.26(Multidisciplinary Sciences)Yoshida, Masahiro*; Ishii, Kenji; Naka, Makoto*; Ishihara, Sumio*; Jarrige, I.*; Ikeuchi, Kazuhiko*; Murakami, Yoichi*; Kudo, Kazutaka*; Koike, Yoji*; Nagata, Tomoko*; et al.
Scientific Reports (Internet), 6, p.23611_1 - 23611_8, 2016/03
Times Cited Count:1 Percentile:11.46(Multidisciplinary Sciences)Murakami, Hiroshi
Journal of Molecular Liquids, 210, Part A, p.37 - 43, 2015/10
Times Cited Count:10 Percentile:38.6(Chemistry, Physical)Picosecond relaxation dynamics of water before and after water shedding from reverse micelles are studied using temperature-dependent terahertz time-domain spectroscopy measurements to clarify the confinement effect of the reverse micelle on the dynamics of water. Before water shedding, the relaxation process due to the collective motion of bulk-like water in the core of the reverse micelle exhibits a considerable slowing down in comparison with that in liquid water as the temperature decreases. This is attributed to the confinement effect of reverse micelles. Moreover, the time constant abruptly drops at the water shedding, and its temperature behavior is similar to that of liquid water afterwards. These results demonstrate that the water extracted from the reverse micelle attains the property of liquid water by reduction in the confinement imposed on the motion of the water.
Kubota, Masato; Yamada, Hiroyuki*; Nakao, Hironori*; Okamoto, Jun*; Yamasaki, Yuichi*; Sawa, Akihito*; Murakami, Yoichi*
Japanese Journal of Applied Physics, 53(5S1), p.05FH07_1 - 05FH07_5, 2014/05
Times Cited Count:2 Percentile:8.84(Physics, Applied)Okamoto, Jun*; Nakao, Hironori*; Yamasaki, Yuichi*; Wadachi, Hiroki*; Tanaka, Arata*; Kubota, Masato; Horigane, Kazumasa*; Murakami, Yoichi*; Yamada, Kazuyoshi*
Journal of the Physical Society of Japan, 83(4), p.044705_1 - 044705_6, 2014/04
Times Cited Count:9 Percentile:55.36(Physics, Multidisciplinary)Hiraishi, Masatoshi*; Iimura, Soshi*; Kojima, Kenji*; Yamaura, Junichi*; Hiraka, Haruhiro*; Ikeda, Kazutaka*; Miao, P.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Miyazaki, Masanori*; et al.
Nature Physics, 10(4), p.300 - 303, 2014/04
Times Cited Count:103 Percentile:95.46(Physics, Multidisciplinary)