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Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro*
Journal of Power and Energy Systems (Internet), 6(2), p.76 - 86, 2012/06
In a sodium-cooled fast reactor (SFR), liquid sodium is used as heat transfer fluid to carry the energy from the reactor core to the steam generation (SG) system for power generation. If the heat transfer tube in the SG is failed, high pressurized water vapor blows into the liquid sodium and the sodium-water reaction (SWR) takes place. The extremely high-temperature reaction jet formed by the SWR, causes damage to the surface of the neighboring heat transfer tubes by thermal and chemical effects. Therefore, it is important to clearly understand the SWR for safety assessment of SG. In this study, we investigated the surface reaction mechanism in the SWR by ab initio method. The potential energy profiles of the dissociations of HO and OH were obtained. The estimated rate constant of the former was much larger than the latter.
Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 11(2), p.147 - 157, 2012/06
A breach of the heat transfer tube in a steam generator (SG) of a sodium-cooled fast reactor results in sodium-water reaction (SWR) by direct contact between liquid sodium and water vapor, which generates high temperature reaction jet. This reaction jet causes damage to the surface of neighboring heat transfer tubes by thermal and chemical effects. Therefore, it is important to clearly understand the SWR for safety assessment of SG. Regarding chemical effect, the surface and gas-phase reaction model are considered. As for the surface reaction, the water vapor encounters the liquid sodium, and the reaction occurs at their interface. Subsequently, the chemical reaction heating vaporizes the liquid sodium, causing the gas-phase reaction. However, there is limited knowledge on surface reaction because of extremely rapid-reaction. Therefore, in this study, ab-initio calculation was performed to evaluate the reaction path on surface reaction in SWR. The reaction path on dissociation of a water molecule at the liquid sodium surface was obtained. In addition, we also confirmed the generation mechanism of hydrogen in the liquid sodium.
Kikuchi, Shin; Ohshima, Hiroyuki; Hashimoto, Kenro*
Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 8 Pages, 2011/10
In a sodium-cooled fast reactor (SFR), liquid sodium is used as heat transfer fluid to carry the energy from the reactor core to the steam generation (SG) system for power generation. If the heat transfer tube in the SG is failed, high pressurized water vapor blows into the liquid sodium and the sodium-water reaction (SWR) takes place. The extremely high temperature reaction jet formed by the SWR causes damage to the surface of the neighboring heat transfer tubes by thermal and chemical effects. Therefore, it is important to clearly understand the SWR for safety assessment of SG. In this work, we studied the surface reaction in the SWR by using ab initio calculations. The successive OH cleavages of a water molecule at the liquid sodium surface were focused. The possible reaction path and the related energies including the barrier heights were reported. The relative rates of the OH cleavages were also discussed.
Saeki, Morihisa; Ishiuchi, Shunichi*; Sakai, Makoto*; Hashimoto, Kenro*; Fujii, Masaaki*
Journal of Physical Chemistry A, 114(42), p.11210 - 11215, 2010/10
Times Cited Count:10 Percentile:32.14(Chemistry, Physical)Kikuchi, Shin; Ohshima, Hiroyuki; Nitta, Hitoshi*; Hashimoto, Kenro*
no journal, ,
no abstracts in English
Kikuchi, Shin; Ohshima, Hiroyuki; Hashimoto, Kenro*; Koike, So*; Uda, Tsuyoshi*; Nishimura, Tamio*
no journal, ,
In order to evaluate failure of the steam generator tube in a sodium cooled fast reactor, JAEA is developing the evaluation system based on the mechanism for sodium-water reaction. Ab-initio molecular dynamics simulation has been performed to analyze potential reaction paths for dominant overall reaction formula to be introduced in the developing evaluation system. This report reveals that we have identified a reaction path and evaluated the rate constant.