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Hirata, Sakiko*; Kusaka, Ryoji; Meiji, Shogo*; Tamekuni, Seita*; Okudera, Kosuke*; Hamada, Shoken*; Sakamoto, Chihiro*; Honda, Takumi*; Matsushita, Kosuke*; Muramatsu, Satoru*; et al.
Inorganic Chemistry, 62(1), p.474 - 486, 2023/01
Times Cited Count：0 Percentile：0.01(Chemistry, Inorganic & Nuclear)Torikawa, Tomoaki*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
Konsoryu, 36(1), p.63 - 69, 2022/03
On free surface of a sodium cooled fast reactor, gas entrainment can be caused by free surface vortices, which may result in disturbance in core power. It is important to develop an evaluation model to predict accurately entrained gas flow rate. In this study, entrained gas flow rate a simple gas entrainment experiment is conducted with focusing on effect of pressure difference between upper and lower tanks. Pressure difference between upper and lower tanks are controlled by changing gas pressure in lower tank. As a result, it is confirmed that the entrained gas flow rate increases with increasing pressure difference between upper and lower tanks. By visualization of swirling annular flow in suction pipe, it is also observed that pressure drop in suction pipe increases with increase in entrained gas flow rate, which implies that entrained gas flow rate can be predicted by evaluation model based on pressure drop in swirling annular flow region.
CoLokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Authelet, G.*; et al.
Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03
Times Cited Count：10 Percentile：69.78(Physics, Nuclear)The structures of the neutron-rich Co isotopes were investigated via (
) knockout reactions at the Radioactive Isotope Beam Factory, RIKEN. Level schemes were reconstructed using the 
coincidence technique, with tentative spin-parity assignments based on the measured inclusive and exclusive cross sections. Comparison with shell-model calculations suggests coexistence of spherical and deformed shapes at low excitation energies in the Co isotopes.
He
excimer cluster tracers in superfluid helium-4 via neutron-
He absorption reactionSonnenschein, V.*; Tsuji, Yoshiyuki*; Kokuryu, Shoma*; Kubo, Wataru*; Suzuki, So*; Tomita, Hideki*; Kiyanagi, Yoshiaki*; Iguchi, Tetsuo*; Matsushita, Taku*; Wada, Nobuo*; et al.
Review of Scientific Instruments, 91(3), p.033318_1 - 033318_12, 2020/03
Times Cited Count：0 Percentile：0(Instruments & Instrumentation)Ito, Kei*; Ito, Daisuke*; Saito, Yasushi*; Ezure, Toshiki; Matsushita, Kentaro; Tanaka, Masaaki; Imai, Yasutomo*
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.6632 - 6642, 2019/08
In this paper, a mechanistic model is proposed to calculate the entrained gas flow rate by a free surface vortex. The model contains the theoretical equation of transient gas core elongation and the empirical equation of critical gas core length for gas bubble detachment. Based on those two equations, the entrained gas flow rate is calculated as the portion of the gas core elongated beyond the critical gas core length per unit time. Then, the mechanistic model was applied to the calculation of the entrained gas flow rate in a simple water experiment. As a result, it is confirmed that the entrained gas flow rate grows rapidly when the liquid (water) flow rate, which determine the strength of a free surface vortex, exceeds a certain threshold value.
He
clusters via neutron-He absorption reaction toward visualization of full velocity field in quantum turbulenceMatsushita, Taku*; Sonnenschein, V.*; Guo, W.*; Hayashida, Hirotoshi*; Hiroi, Kosuke; Hirota, Katsuya*; Iguchi, Tetsuo*; Ito, Daisuke*; Kitaguchi, Masaaki*; Kiyanagi, Yoshiaki*; et al.
Journal of Low Temperature Physics, 196(1-2), p.275 - 282, 2019/07
Times Cited Count：1 Percentile：4.76(Physics, Applied)
Ni from the (
,
) reactionElekes, Z.*; Kripk
, 
*; Sohler, D.*; Sieja, K.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Doornenbal, P.*; Obertelli, A.*; Authelet, G.*; Baba, Hidetada*; et al.
Physical Review C, 99(1), p.014312_1 - 014312_7, 2019/01
Times Cited Count：10 Percentile：64.15(Physics, Nuclear)The nuclear structure of the Ni nucleus was investigated by (,) reaction using a NaI(Tl) array to detect the deexciting prompt 
rays. A new transition with an energy of 2227 keV was identified by 
and 
coincidences. Our shell-model calculations using the Lenzi, Nowacki, Poves, and Sieja interaction produced good candidates for the experimental proton hole states in the observed energy region, and the theoretical cross sections showed good agreement with the experimental values. Although we could not assign all the experimental states to the theoretical ones unambiguously, the results are consistent with a reasonably large Z = 28 shell gap for nickel isotopes in accordance with previous studies.
=28 and 
=50; Spectroscopy of 
ZnShand, C. M.*; Podoly
k, Zs.*; Grska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.
Physics Letters B, 773, p.492 - 497, 2017/10
Times Cited Count：25 Percentile：87.36(Astronomy & Astrophysics)
atoms at the wall on the production profile of H
ions in large negative ion sourcesTakado, Naoyuki*; Matsushita, Daisuke*; Fujino, Ikuro*; Hatayama, Akiyoshi*; Tobari, Hiroyuki; Inoue, Takashi
Review of Scientific Instruments, 79(2), p.02A503_1 - 02A503_4, 2008/02
Times Cited Count：2 Percentile：14.59(Instruments & Instrumentation)Production and transport process of the H atoms are numerically simulated using a three-dimensional Monte Carlo transport code. The code was applied to the "JAEA 10 ampere negative ion source" under Cs-seeded condition to obtain a spatial distribution of surface-produced H ions. In this analysis, we focus on the effect of the energy relaxation of the H atoms at the wall on the H ion production from the H atoms. The result indicates that, by considering the energy relaxation of the H atoms at the wall, the production profile of the surface-produced H ion is well reflected in the production profile of the H atom production.
ion transport processes in Cs-seeded negative ion sourcesMatsushita, Daisuke*; Takado, Naoyuki*; Hatayama, Akiyoshi*; Inoue, Takashi
Review of Scientific Instruments, 79(2), p.02A527_1 - 02A527_4, 2008/02
Times Cited Count：5 Percentile：28.3(Instruments & Instrumentation)The H ion transport processes are numerically simulated to understand the extraction process of surface-produced H ions. The three-dimensional transport code using Monte Carlo method has been applied to calculate the H ion extraction probabilities in the model geometry of the JAEA 10 ampere negative ion source. The roles of (1) filter magnetic field and (2) collisions with neutrals (H atoms and H molecules) on the H ion extraction are systematically studied. The results show that H ions are extracted mainly by the filter magnetic field under the low gas pressure condition. The simulation results of extracted H ion beam intensity in the JAEA 10 ampere negative ion source without the magnetic filter tend to be smaller than the experimental results, especially under the low pressure condition.
Ishino, Masahiko; Namikawa, Kazumichi; Matsushita, Mitsuyoshi*; Owada, Kenji; Shimizu, Daisuke*; Sakamoto, Junya*; Mizuki, Junichiro
no journal, ,
no abstracts in English
Torikawa, Tomoaki*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
no journal, ,
On free surface of a sodium cooled fast reactor, gas entrainment can be caused by free surface vortices, which may result in disturbance in core power. It is important to develop an evaluation model to predict accurately entrained gas flow rate. In this study, the effect of pressure gradient in vortex axis direction on the gas entrainment flow rate is investigated in a simple gas experimental apparatus, in which upper and lower tanks are connected by a suction pipe. As a result, it was observed that there are two flow regime: swirling annular flow regime shows the tendency that only the gas entrainment flow rate increases with almost constant pressure gradient, then, when liquid plug is induced by the development of free surface disturbance, the gas entrainment flow rate increases as the pressure gradient increases. In addition, it was confirmed that the transformation of those two flow regimes is advanced by higher liquid level in the upper tank.
Ito, Kei*; Ito, Daisuke*; Odaira, Naoya*; Saito, Yasushi*; Song, K.*; Ezure, Toshiki; Matsushita, Kentaro; Tanaka, Masaaki
no journal, ,
The entrained gas flow rate by a bathtub vortex must be evaluated to achieve stable operation of a sodium-cooled fast reactor. In this study, a simple vortex-type gas entrainment experiment is conducted to evaluated the entrained gas flow rate under various conditions of free surface level, downstream pressure and suction pipe diameter. As a result, it is clarified that the entrained gas flow rate increases with the decrease in the downstream pressure. Based on the experimental result, we model the annular two-phase flow in the suction pipe and propose a new evaluation model of the entrained gas flow rate in which the influence of the downstream pressure.
Ito, Kei*; Odaira, Naoya*; Ito, Daisuke*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki
no journal, ,
In a sodium-cooled fast reactor, the inflow of entrained gas by a free surface vortex in the reactor vessel into the reactor core may cause reactivity disturbance. Therefore, a method to evaluate the gas entrainment (GE) volume flow rate is required in the design of fast reactors. In this study, as part of the investigation of the mechanism determining the GE volume flow rate, the numerical analysis targeting the free surface vortex in an experimental system in which the upper and lower cylindrical containers are connected by piping was performed, and the GE volume flow rate under various pressure conditions was evaluated. As the result, it was confirmed that the change in GE volume flow rate when the pressure difference between the upper and lower containers was changed was consistent between the experimental and analysis results, and that the GE volume flow rate could be evaluated by numerical analysis.
