JOPSS - Search Results

Journal Articles

Multi-dimensional characteristics of upward bubbly flows in a vertical large-size square channel

Sun, Haomin; Kunugi, Tomoaki*; Yokomine, Takehiko*; Shen, X.*; Hibiki, Takashi*

International Journal of Heat and Mass Transfer, 211, p.124214_1 - 124214_17, 2023/09

https://doi.org/10.1016/j.ijheatmasstransfer.2023.124214

Times Cited Count：2 Percentile：53.66(Thermodynamics)

Journal Articles

A Study on self-terminating behavior of sodium-concrete reaction, 2

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 55(8), p.874 - 884, 2018/08

https://doi.org/10.1080/00223131.2018.1449677

Times Cited Count：4 Percentile：38.11(Nuclear Science & Technology)

As parts of severe accident studies in sodium-cooled fast reactor, experiments were performed to investigate the termination mechanism of sodium-concrete reaction (SCR). In the experiment, the reaction time was controlled to investigate the distribution change of sodium (Na) and the reaction products in the pool and around the reaction front. In the results, the Na around the reaction front decreased from the enough amount with the reaction time. The concentrations were 18-24 wt.% for Na, and 22-18 wt.% for Si after the termination. From the thermodynamics calculations, the stable materials around the reaction front comprised more than 90 wt.% solid products such as Na $_{2}$ SiO $_{3}$ , and no Na. Further, the distribution of Na and reaction products could be explained by a steady-state sedimentation-diffusion model. At the early stage of SCR, the reaction products were suspended as particles in the Na pool because of the high H $_{2}$ -generation rate. As the concrete ablation proceeds, they start settling down due to the decreased H $_{2}$ -generation rate, thereby allowing SCR termination. It was concluded that SCR termination was caused by the sediment of the reaction products and the lack of Na around the reaction front.

Journal Articles

Anthropogenic radionuclides in seawater of the Japan Sea; The Results of recent observations and the temporal change of concentrations

Ito, Toshimichi; Aramaki, Takafumi*; Otosaka, Shigeyoshi; Suzuki, Takashi; Togawa, Orihiko; Kobayashi, Takuya; Kawamura, Hideyuki; Amano, Hikaru; Senju, Tomoharu*; Chaykovskaya, E. L.*; et al.

Journal of Nuclear Science and Technology, 42(1), p.90 - 100, 2005/01

https://doi.org/10.3327/jnst.42.90

Times Cited Count：14 Percentile：67.75(Nuclear Science & Technology)

During 1996-2002, a wide-area research project on anthropogenic radionuclides was done in the Japanese and Russian EEZ of the Japan Sea to investigate their migration. As the results of expeditions in 2001 and 2002, (1) the concentrations and distributions of radionuclides are similar to the results of previous, (2) inventories of these radionuclides indicate accumulation in the Japan Sea seawater compared to the amounts supplied by global fallout, (3) $^{90}$ Sr and $^{137}$ Cs concentrations in intermediate layer show temporal variations, and 4) the variations may reflect the water mass movement in upper part of the Japan Sea.

Journal Articles

Coupled hydrogen moderator optimization with ortho/para hydrogen ratio

Kai, Tetsuya; Harada, Masahide; Teshigawara, Makoto; Watanabe, Noboru; Ikeda, Yujiro

Nuclear Instruments and Methods in Physics Research A, 523(3), p.398 - 414, 2004/05

https://doi.org/10.1016/j.nima.2003.11.427

Times Cited Count：36 Percentile：89.19(Instruments & Instrumentation)

Neutronic performance of a coupled hydrogen moderator was studied as a function of para hydrogen concentration, moderator thickness, height and premoderator thickness. It was found that a thick (120140mm) moderator with 100% para hydrogen was optimal to provide the highest time- and energy- integrated neutron intensity below 15 meV together with the highetst possible pulse-peak intensity. Low-energy neutron distribution on the moderator viewed surface was found to exhibit an intensity-enhanced region at a picture frame part near premoderator. The rather peculiar distribution suggested that the moderator and the viewed surface must be designed so as to take the brighter region near premoderator in use.

Journal Articles

Studies on two types of built-in inhomogeneities for polymer gels; Frozen segmental concentration fluctuations and spatial distribution of cross-links

Norisue,Tomohisa*; Kida, Yusuke*; Masui, Naoki*; Tran-Cong-Miyata, Q.*; Maekawa, Yasunari; Yoshida, Masaru; Shibayama, Mitsuhiro*

Macromolecules, 36(16), p.6202 - 6212, 2003/08

https://doi.org/10.1021/ma030067h

Times Cited Count：76 Percentile：89.41(Polymer Science)

The shrinking kinetics of poly(N-isopropylacrylamide) (PNIPA) gels has been studied for two types of PNIPA gels prepared by (i) copolymerization of constituent monomer and cross-linker and (ii) -ray irradiation in the PNIPA solutions in order to investigate the role of cross-linking on shrinking kinetics. The shrinking kinetics of the monomer cross-linked gels is quite similar to that of the polymer cross-linked gels. On the other hand, a significant difference was found when the microscopic structure and the dynamics were investigated by small-angle neutron scattering (SANS) and static/dynamic light scattering (SLS/DLS). The degree of built-in inhomogeneities and dynamic fluctuations were evaluated as a function of the cross-linking degree and the gel preparation temperature by intensity decomposition methods for both types of gels. It is concluded that the monomer cross-linked gels have extra built-in inhomogeneities due to the spatial distribution of crosslinks in addition to the frozen concentration fluctuations inherent in polymer gels.