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Ikuta, Daijo*; Otani, Eiji*; Sano, Asami; Shibazaki, Yuki*; Terasaki, Hidenori*; Yuan, L.*; Hattori, Takanori
Scientific Reports (Internet), 9, p.7108_1 - 7108_8, 2019/05
Times Cited Count：38 Percentile：92.44(Multidisciplinary Sciences)Hydrogen is likely one of the light elements in the Earth's core. Despite its importance, no direct observation has been made of hydrogen in an iron lattice at high pressure. We made the first direct determination of site occupancy and volume of interstitial hydrogen in a face-centered cubic (fcc) iron lattice up to 12 GPa and 1200 K using the in situ neutron diffraction method. At pressures 
5 GPa, the hydrogen content in the fcc iron hydride lattice (x) was small at x 0.3, but increased to x 
0.8 with increasing pressure. Hydrogen atoms occupy both octahedral (O) and tetrahedral (T) sites; typically 0.870 in O-sites and 0.057 in T-sites at 12 GPa and 1200 K. The fcc lattice expanded approximately linearly at a rate of 2.22 
per hydrogen atom, which is higher than previously estimated (1.9 /H). The lattice expansion by hydrogen dissolution was negligibly dependent on pressure. The large lattice expansion by interstitial hydrogen reduced the estimated hydrogen content in the Earth's core that accounted for the density deficit of the core. The revised analyses indicate that whole core may contain hydrogen of 80 times of the ocean mass with 79 and 0.8 ocean mass for the outer and inner cores, respectively.
Takayama, Yusuke*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Taki, Tomihiro; Sakao, Ryota; Ichikawa, Yasuaki*
Unsaturated Soils; Research & Applications, p.659 - 665, 2014/06
In this paper, a multiple unsaturated soil barrier consisting of gravel, sand and bentonite-mixed soil layers is considered as a hardly permeable covering to prevent rainwater from infiltrating into waste deposits. Not only the quite low permeability of bentonite-mixed soil layer but also a function of capillary barrier between granular layers having different water-retention capabilities is expected to prevent water infiltration. A series of numerical simulation is carried out to evaluate performance of the multiple soil barrier using saturated/unsaturated soil/water coupled FE computation technique. The multiple unsaturated soil barrier system considered here is 10m long and 1.5 m thick consisting of sandy soil surface, sand filter, gravel layer, sand filter and bentonite-mixed clayey layer. And the soil barrier system is assumed to be placed as a covering with a 5% inclination on the waste deposit. The performance of the multiple soil barrier system is shown as a management chart to maintain impermeable ability associated with possible rainfall intensity. Particularly, in this paper, actual rainfall record in Okayama area is employed to determine the rainfall intensity which is imposed as a boundary condition in the computation. According to the simulation results, it is found that the capillary barrier is a key issue in evaluating the long term performance of the barrier system. And, it is confirmed that the barrier system considered in this paper can work well against the maximum intensity of the rainfall in the past record.
Ohgama, Kazuya; Ando, Yoko; Yamaguchi, Mika; Ikuta, Yuko; Shinohara, Nobuo; Murakami, Hiroyuki; Yamashita, Kiyonobu; Uesaka, Mitsuru*; Demachi, Kazuyuki*; Komiyama, Ryoichi*; et al.
JAEA-Review 2013-004, 76 Pages, 2013/05
JAEA-Review-2013-004.pdf:13.53MB
JAEA together with the Japan Nuclear Human Resource Development Network (JN-HRD Net), the University of Tokyo (UT) and the Japan Atomic Industrial Forum (JAIF) cohosted the IAEA-Nuclear Energy Management School in Tokai Village, aiming that Japan will be the center of nuclear HRD in the Asian region. In the school, not only lectures by IAEA experts, but also lectures by Japanese experts and technical visits were included for foreign participants. The school contributed to the internationalization of Japanese young professionals, development of nuclear human resource of other countries, and enhancement of cooperation between IAEA and Japan. Additionally, collaborative relationship within JN-HRD Net was strengthened by the school. In this report, findings obtained during the preparatory work and the school period are reported for future international nuclear HRD activities in Japan.
Okura, Takehisa; Oishi, Tetsuya; Taki, Mitsumasa; Shibanuma, Yukio; Kikuchi, Masamitsu; Akino, Hitoshi; Kikuta, Yasuaki; Kawasaki, Masatsugu; Saegusa, Jun; Tsutsumi, Masahiro; et al.
JAEA-Data/Code 2012-010, 37 Pages, 2012/05
JAEA-Data-Code-2012-010.pdf:2.28MB
Due to the accident at Fukushima Daiichi Nuclear Power Plant caused by the 2011 off the Pacific coast of Tohoku Earthquake occurred at 11th March 2011, the emergency environmental radiation monitoring was conducted at Nuclear Science Research Institute, Japan Atomic Energy Agency (JAEA). This report provides the monitoring results of ambient 
-ray dose rate and atmospheric radioactivity concentration until the beginning of June 2011. Some anthropogenic radionuclides such as Cs-134, Cs-137, I-131, I-132, Te-132, Xe-133 and others were detected from air samples. The atmospheric radioactivity concentrations varied with some peaks corresponded with that of ambient -ray dose rate after 15th March 2011. Composition of each peak showed various characteristic. Internal exposure caused by inhalation was estimated from the observed atmospheric radioactivity.
Yoshida, Hiroyuki; Suzuki, Takayuki*; Takase, Kazuyuki; Ikuta, Ryuhei*; Koizumi, Yasuo*
Dai-16-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.103 - 106, 2011/06
no abstracts in English
Matsuura, Hideharu*; Iwata, Hiroshi*; Kagamihara, So*; Ishihara, Ryohei*; Yoneda, Masahiko*; Imai, Hideaki*; Kikuta, Masanori*; Inoue, Yuki*; Hisamatsu, Tadashi*; Kawakita, Shiro*; et al.
Japanese Journal of Applied Physics, Part 1, 45(4A), p.2648 - 2655, 2006/04
Times Cited Count：15 Percentile：49.28(Physics, Applied)no abstracts in English
Ikuta, Ryuhei*; Koizumi, Yasuo*; Takase, Kazuyuki
no journal, ,
no abstracts in English
Miyashita, Tomonori*; Ikuta, Hiroki*; Suzuki, Hiroshi*; Takai, Kenichi*; Hagihara, Yukito*; Hirade, Tetsuya
no journal, ,
The effect of hydrogen existence on the formation of lattice defects by the strain for pure iron and cold-drawn pearlite steel. The thermal desorption analysis (TDA) of hydrogen and the positron annihilation lifetime measurements gave that the interaction between hydrogen and strain could enhance the formation of the lattice defects for pure iron. TDA gave the same results even for the cold-drawn pearlite steel.
Ikuta, Ryuhei*; Koizumi, Yasuo*; Takase, Kazuyuki
no journal, ,
no abstracts in English
Yoshida, Hiroyuki; Suzuki, Takayuki*; Takase, Kazuyuki; Ikuta, Ryuhei*; Koizumi, Yasuo*
no journal, ,
no abstracts in English
Ikuta, Ryuhei*; Koizumi, Yasuo*; Yoshida, Hiroyuki; Takase, Kazuyuki
no journal, ,
no abstracts in English
Oishi, Tetsuya; Kikuchi, Masamitsu; Takahashi, Kenichi; Okura, Takehisa; Akino, Hitoshi; Kawasaki, Masatsugu; Kikuta, Yasuaki; Saegusa, Jun; Shibanuma, Yukio; Yamamoto, Hideaki
no journal, ,
no abstracts in English
Ikuta, Yuki*; Takayama, Yusuke*; Tsurumi, Shuhei*; Ichikawa, Yasuaki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Taki, Tomihiro; Sakao, Ryota
no journal, ,
As a part of remediation of closed uranium mine, "Yotsugi Mill Tailings Pond" has been remediated in Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency. The aim of remediation is to take measures to reduce the load of water treatment and the radon exposure to humans in future, and to prevent the occurrence of relevant environmental contamination. So far, the upstream of the Pond has been covered by the multi-layered capping in which layers are set to use gravel, sand and decomposed granite soil to drain penetrated rainwater to the neighboring river. This capping system needs to be monitored on a long-term basis and to be evaluated to work as expected in advance, therefore seepage analysis and settlement analysis has carried out. As a result, Settlement of analysis was well accorded with measured value and marked change of saturation accompanied by rain was not observed in the seepage analysis.
Sasaki, Yosuke*; Takayama, Yusuke*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Sakao, Ryota; Taki, Tomihiro
no journal, ,
As part of environmental remediation of Ningyo-toge Uranium Mine, multi-layered capping is constructed to reduce rainwater infiltration at the upstream of the Mill Tailings Pond. Settlement is expected due to consolidation characteristics of mill tailings and clayish sediments which exist below capping. Numerical simulation is carried out to expect the settlement amount during and after the capping construction. Settlement amount has been measured periodically, and the simulation result and measurement data are compared to evaluate the simulation method.
Okada, Mariko*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Sakao, Ryota; Ohara, Yoshiyuki
no journal, ,
no abstracts in English
