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Shiomi, Yuki*; Otani, Takashi*; Iguchi, Satoshi*; Sasaki, Takahiko*; Qiu, Z.*; Nakayama, Hiroyasu*; Uchida, Kenichi*; Saito, Eiji
Applied Physics Letters, 104(24), p.242406_1 - 242406_5, 2014/06
Times Cited Count：31 Percentile：73.52(Physics, Applied)Oda, Chie; Honda, Akira; Takase, Hiroyasu*; Ozone, Kenji*; Sasaki, Ryoichi*; Yamaguchi, Kohei*; Sato, Tsutomu*
Nendo Kagaku, 51(2), p.34 - 49, 2013/02
Proposed TRU repository designs for geological disposal envisage the use of a bentonite buffer to limit the migration of radionuclides by impeding groundwater flow. Under highly alkaline conditions due to cementitious materials could cause a complex series of coupled changes in the porewater chemistry, mineralogy and, ultimately, the mass transport properties of the bentonite buffer. To elucidate the consequences of these coupled changes, reactive-transport model analyses have been conducted for eight bentonite alteration test cases using different combinations of secondary minerals that could form in the bentonite buffer. It was found that after 100,000 years the amount of dissolved bentonite was at a maximum when metastable secondary minerals precipitated. It was also found that the diffusion and hydraulic coefficients after 100,000 years in all test cases were on the same order of magnitude as the initial values.
Kume, Tetsuji*; Machida, Akihiko; Aoki, Katsutoshi; Sasaki, Shigeo*; Shimizu, Hiroyasu*
Koatsuryoku No Kagaku To Gijutsu, 21(3), p.184 - 189, 2011/09
Raman and visible absorption spectra of rare earth trihydrides have been measured at high pressures, in order to investigate the structural and electronic phase transitions. The successive phase transitions of hcp-intermediatefcc phase were confirmed by Raman measurements. From the visible absorption experiments, the band gap energy was estimated. The gap closure was found to occur on the transition from the intermediate to the fcc phase.
Takahashi, Eiichi*; Kato, Susumu*; Furutani, Hirohide*; Sasaki, Akira; Kishimoto, Yasuaki*; Takada, Kenji*; Matsumura, Satoshi*; Sasaki, Hiroyasu*
Journal of Physics D; Applied Physics, 44(30), p.302001_1 - 302001_4, 2011/08
Times Cited Count：7 Percentile：29.62(Physics, Applied)A recently developed ultrafast camera that can acquire 
frames per second was used to investigate positive streamer discharge. It enabled single-shot evaluation of streamer evolution without the need to consider shot-to-shot reproducibility. This camera was used to investigate streamers in argon. Growing branches, the transition when a streamer forms a return stroke, and related phenomena were clearly observed.
; Raman, infrared, and visible absorption spectroscopyKume, Tetsuji*; Oura, Hiroyuki*; Takeichi, Tomoo*; Omura, Ayako*; Machida, Akihiko; Watanuki, Tetsu; Aoki, Katsutoshi; Sasaki, Shigeo*; Shimizu, Hiroyasu*; Takemura, Kenichi*
Physical Review B, 84(6), p.064132_1 - 064132_7, 2011/08
Times Cited Count：21 Percentile：62.22(Materials Science, Multidisciplinary)Raman, IR, and visible absorption spectra of scandium trihydride (ScH) have been measured at high pressures up to 50 GPa at room temperature. The structural and electronic phase transitions were investigated. Successive hcp-intermediate-fcc phase transitions took place at 25 and 46 GPa. It was suggested that the intermediate phase of ScH has the same structure as that of YH. The energy gap of ScH is 1.7 eV at the ambient condition and is closed around 50 GPa, at which the crystal structure transforms to fcc.
by Raman and visible absorption spectroscopyKume, Tetsuji*; Oura, Hiroyuki*; Sasaki, Shigeo*; Shimizu, Hiroyasu*; Omura, Ayako*; Machida, Akihiko; Watanuki, Tetsu; Aoki, Katsutoshi; Takemura, Kenichi*
Physical Review B, 76(2), p.024107_1 - 024107_5, 2007/07
Times Cited Count：40 Percentile：79.22(Materials Science, Multidisciplinary)Raman and visible absorption spectra of YH were measured at high pressures, in order to clarify the structural and electronic phase transitions. The Raman results revealed the presence of an intermediate phase at 9-24 GPa between the low-pressure hexagonal and high-pressure fcc phases. The Y-framework structure and the positions of interstitial H atoms are changed on the transition to the intermediate phase. The results of the absorption measurements demonstrate that the optical band gap begins to close in response to the phase transition.
Oda, Chie; Sasaki, Ryoichi; Takase, Hiroyasu*; Savage, D.*; Honda, Akira
Proceedings of International Workshop on Waste Management in Sapporo, p.163 - 165, 2005/08
The uncertainty in our understanding of the precise mineral paragenetic sequences of the interaction of bentonite with hyperalkaline fluids in the long-term still remains. In order to reflect this uncertainty, multiple scenarios of bentonite alteration were investigated based on the possible mineralogical changes derived from knowledge of both experiments and observation of natural systems.
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reactions for 
=1.5-2.4 GeVZegers, R. G. T.*; Sumihama, Mizuki*; Ahn, D. S.*; Ahn, J. K.*; Akimune, Hidetoshi*; Asano, Yoshihiro; Chang, W. C.*; Dat
, S.*; Ejiri, Hiroyasu*; Fujimura, Hisako*; et al.
Physical Review Letters, 91(9), p.092001_1 - 092001_4, 2003/08
Times Cited Count：128 Percentile：94.52(Physics, Multidisciplinary)no abstracts in English
= +1 Baryon resonance in photoproduction from the neutronNakano, Takashi*; Ahn, D. S.*; Ahn, J. K.*; Akimune, Hidetoshi*; Asano, Yoshihiro; Chang, W. C.*; Date, S.*; Ejiri, Hiroyasu*; Fujimura, Hisako*; Fujiwara, Mamoru; et al.
Physical Review Letters, 91(1), p.012002_1 - 012002_4, 2003/07
Times Cited Count：1024 Percentile：99.84(Physics, Multidisciplinary)no abstracts in English
; Umeki, Hiroyuki; Takase, Hiroyasu; Yui, Mikazu; Sasaki, Noriaki;
The Second Annual International High Level Radioa, 2, 1715 Pages, 1991/00
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Ouchi, Masayuki; Hoshi, Takahiro; Sasaki, Shunichi; Isobe, Hiroyasu; Nagaoka, Shinichi; Kurabayashi, Kazuaki; Obu, Tomoyuki
no journal, ,
Plutonium nitrate solution is stored in tanks that have cooling system to prevent boiling accident by decay heat and scavenging system to prevent explosion of hydrogen generated by radiolysis. These systems are designed to be provided power from emergency power generators at the Tokai Reprocessing Plant (TRP) when commercial power is lost. In addition, some apparatus (mobile power generators and nitrogen gas cylinder to scavenge hydrogen, etc.) are recently deployed at TRP on the basis of power loss in Fukushima Daiichi nuclear accident. In this report, these safety measures for emergency are shown.
