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Yamashita, Keishiro*; Komatsu, Kazuki*; Klotz, S.*; Fabelo, O.*; Fernndez-Daz, M. T.*; Abe, Jun*; Machida, Shinichi*; Hattori, Takanori; Irifune, Tetsuo*; Shimmei, Toru*; et al.
Proceedings of the National Academy of Sciences of the United States of America, 119(40), p.e2208717119_1 - e2208717119_6, 2022/10
Times Cited Count:2 Percentile:19.02(Multidisciplinary Sciences)Here we present the first elucidation of the disordered structure of ice VII, the dominant high-pressure form of water, at 2.2 GPa and 298 K from both single-crystal and powder neutron diffraction techniques. We reveal the three-dimensional atomic distributions from the maximum entropy method and unexpectedly find a ring-like distribution of hydrogen in contrast to the commonly-accepted discrete sites. In addition, total scattering analysis at 274 K clarified the difference in the intermolecular structure from ice VIII, the ordered counterpart of ice VII, despite an identical molecular geometry. Our complementary structure analyses robustly demonstrate the unique disordered structure of ice VII. Furthermore, these noble findings are related to the proton dynamics which drastically vary with pressure, and will contribute to an understanding of the structural origin of anomalous physical properties of ice VII under pressures.
Yamashita, Keishiro*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Irifune, Tetsuo*; Shimmei, Toru*; Sugiyama, Kazumasa*; Kawamata, Toru*; Kagi, Hiroyuki*
High Pressure Research, 42(1), p.121 - 135, 2022/03
Times Cited Count:3 Percentile:54.42(Physics, Multidisciplinary)Yamato, Masaaki; Sugiyama, Tomoyuki; Nagase, Fumihisa
no journal, ,
To confirm the reactor safety design, safety reviews are performed under accident conditions as well as under normal operation conditions. One of such Design Basis Accidents is the Loss-of-Coolant Accident (LOCA) in which the reactor coolant water is lost typically due to a pipe break. This presentation shows the concept of the current LOCA safety regulation, and presents the results from the recently started experiments on mechanical properties of post-LOCA cladding, breakaway phenomenon in cladding high temperature oxidation, and influence of sea water on the cladding high temperature oxidation.