Preparation, thermoelectric properties, and crystal structure of boron-doped MgSi single crystals

Hayashi, Kei*; Saito, Wataru*; Sugimoto, Kazuya*; Oyama, Kenji*; Hayashi, Koichi*; Happo, Naohisa*; Harada, Masahide; Oikawa, Kenichi; Inamura, Yasuhiro; Miyazaki, Yuzuru*

AIP Advances (Internet), 10(3), p.035115_1 - 035115_7, 2020/03

https://doi.org/10.1063/1.5143839

Round Robin test for the determination of nitrogen concentration in solid lithium

Favuzza, P.*; Antonelli, A.*; Furukawa, Tomohiro; Groeschel, F.*; Heidinger, R.*; Higashi, Takuma*; Hirakawa, Yasushi; Iijima, Minoru; Ito, Yuzuru; Kanemura, Takuji; et al.

Fusion Engineering and Design, 107, p.13 - 24, 2016/06

https://doi.org/10.1016/j.fusengdes.2016.03.026

Three different partners, ENEA, JAEA and University of Tokyo, have been involved during 2014 and 2015 in the Round Robin experimentation for the assessment of the soundness of the analitycal procedure for the determination of the Nitrogen impurities contained inside a solid Lithium sample. Two different kinds of Lithium samples, differing by about an order of magnitude in Nitrogen concentration (about 230 wppm, about 20-30 wppm), have been selected for this cross analysis. The agreement of the achieved results appears very good for what concerns the most concentrated Lithium and indicates each partner's procedure is appropriate and intrinsically able to lead to meaningful values, characterized by a relative uncertainty of just few %. The smaller agreement in the case of the less concentrated Lithium anyway points out that particular attention must be paid to reduce as much as possible any source of external contamination and highlights the importance of the proper blank subtraction.

Crack growth behavior of F82H steel in the 288C water

Ito, Yuzuru; Saito, Masahiro*; Abe, Katsunori*; Wakai, Eiichi

Journal of Plasma and Fusion Research SERIES, Vol.11, p.73 - 78, 2015/03

http://www.jspf.or.jp/JPFRS/PDF/Vol11/jpfrs2015_11-073.pdf

Crack growth is a one of the key mechanical properties for the design evaluation in fusion materials to be tested at the High Flux Test Module (HFTM) in IFMIF. In this study, crack growth rate of the F82H steel in the 288C water was investigated by using an almost standard size specimen in order to avoid the specimen size effect on the crack growth. It was found that the typical intergranular fracture surface could be obtained during the crack propagation even at room temperature. Chromium carbide, CrC, precipitation along the grain boundaries in F82H steel may influence the intergranular fracture under the fatigue crack propagation at room temperature in air. The possible evidence of crack growth in the 288C water was also observed. The crack growth rate at 30 MPa in the 288C water was conservatively estimated to about 710 m/s. Further systematic study of crack growth, and the improvement of surface finishing against crack propagation are necessary for the design evaluation in fusion materials.

Status of development of Lithium Target Facility in IFMIF/EVEDA project

Wakai, Eiichi; Kondo, Hiroo; Kanemura, Takuji; Hirakawa, Yasushi; Furukawa, Tomohiro; Hoashi, Eiji*; Fukada, Satoshi*; Suzuki, Akihiro*; Yagi, Juro*; Tsuji, Yoshiyuki*; et al.

Proceedings of Plasma Conference 2014 (PLASMA 2014) (CD-ROM), 2 Pages, 2014/11

In the IFMIF/EVEDA (International Fusion Materials Irradiation Facility/ Engineering Validation and Engineering Design Activity), the validation tests of the EVEDA lithium test loop with the world's highest flow rate of 3000 L/min was succeeded in generating a 100 mm-wide and 25 mm-thick free-surface lithium flow steadily under the IFMIF operation condition of a high-speed of 15 m/s at 250C in a vacuum of 10 Pa. Some excellent results of the recent engineering validations including lithium purification, lithium safety, and remote handling technique were obtained, and the engineering design of lithium facility was also evaluated. These results will advance greatly the development of an accelerator-based neutron source to simulate the fusion reactor materials irradiation environment as an important key technology for the development of fusion reactor materials.

Thermal stability of butt joint for CS conductor in JT-60SA

Takao, Tomoaki*; Kawahara, Yuzuru*; Nakamura, Kazuya*; Yamamoto, Yusuke*; Yagai, Tsuyoshi*; Murakami, Haruyuki; Yoshida, Kiyoshi; Natsume, Kyohei*; Hamaguchi, Shinji*; Obana, Tetsuhiro*; et al.

IEEE Transactions on Applied Superconductivity, 24(3), p.4800804_1 - 4800804_4, 2014/06

https://doi.org/10.1109/TASC.2013.2284020

no abstracts in English

Development of small specimen test techniques for the IFMIF test cell

Wakai, Eiichi; Kim, B. J.; Nozawa, Takashi; Kikuchi, Takayuki; Hirano, Michiko*; Kimura, Akihiko*; Kasada, Ryuta*; Yokomine, Takehiko*; Yoshida, Takahide*; Nogami, Shuhei*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 6 Pages, 2013/03

https://inis.iaea.org/collection/NCLCollectionStore/_Public/44/060/44060304.pdf?r=1&r=1#page=596

Standard for prevention of gas entrainment phenomena in fast reactors, 1; Validations of CFD methods for reproducibilities of gas entrainment phenomena

Ohshima, Hiroyuki; Tanaka, Nobuatsu*; Eguchi, Yuzuru*; Nishimura, Motohiko*; Kunugi, Tomoaki*; Uchibori, Akihiro; Ito, Kei; Sakai, Takaaki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 11(4), p.316 - 328, 2012/12

https://doi.org/10.3327/taesj.J11.047

It is of importance for stable operations of sodium-cooled fast reactors (SFRs) to prevent gas entrainment (GE) phenomena due to free surface vortices. Therefore, the authors have been developing an evaluation method for GE based on computational fluid dynamics (CFD) methods. In this study, we determine the suitable CFD method for GE phenomena from several candidates through some numerical benchmarks. As the results, we obtain the following guideline for the vortex-induced gas entrainment. Free vortex flow around the vortex core can be correctly evaluated by using the appropriate numerical models such as enough mesh resolution, suitable advection solver, suitable turbulence and free surface modeling.

Partial gap opening on the Fermi surface of the noncentrosymmetric superconductor MoAlC

Koyama, Takehide*; Ozaki, Yuzuru*; Ueda, Koichi*; Mito, Takeshi*; Kohara, Takao*; Waki, Tsuyoshi*; Tabata, Yoshikazu*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Suzuki, Michito; et al.

Physical Review B, 84(21), p.212501_1 - 212501_4, 2011/12

https://doi.org/10.1103/PhysRevB.84.212501

The results of Al nuclear magnetic resonance and specific-heat measurements of the noncentrosymmetric superconductor MoAlC are reported. The phase transition around 130 K is inferred from a distinct change in the NMR spectrum, a clear peak in the spin-echo decay rate, and an anomaly in the specific heat. Possibility of charge-density wave ordering around 130 K is discussed by calculating the Fermi surfaces in the normal states and considering the partial quenching of the Fermi surfaces with the decrease in 1/ below the superconducting transition temperature.

Improvement of gas entrainment prediction method; Introduction of surface tension effect

Ito, Kei; Sakai, Takaaki; Eguchi, Yuzuru*; Monji, Hideaki*; Ohshima, Hiroyuki; Uchibori, Akihiro; Xu, Y.*

Journal of Nuclear Science and Technology, 47(9), p.771 - 778, 2010/09

https://doi.org/10.3327/jnst.47.771

A gas entrainment (GE) prediction method has been developed to establish design criteria for the large-scale sodium-cooled fast reactor (JSFR) systems. In this paper, the evaluation accuracy of gas core lengths is improved by introducing the surface tension effects into the prototype GE prediction method. For the improvement, the mechanical balance between gravitational, centrifugal, and surface tension forces is considered. The improved GE prediction method is validated by analyzing the gas core lengths observed in simple experiments. Results show that the analytical gas core lengths calculated by the improved GE prediction method become shorter in comparison to the prototype GE prediction method, and are in good agreement with the experimental data. In addition, the experimental data under different temperature and surfactant concentration conditions are reproduced by the improved GE prediction method.

Proposal of design criteria for gas entrainment from vortex dimples based on a computational fluid dynamics method

Sakai, Takaaki; Eguchi, Yuzuru*; Monji, Hideaki*; Ito, Kei; Ohshima, Hiroyuki

Heat Transfer Engineering, 29(8), p.731 - 739, 2008/08

https://doi.org/10.1080/01457630801981739

Design criteria for gas entrainments (GE) from the liquid surface in a fast breeder reactor system were proposed in this paper for the two types of GE phenomena from a vortex dimple based on a computational fluid dynamics (CFD) method. The first gas entrainment phenomenon is a gas core extension directly to the outlet piping level, which induces large amount of GE to the flow system. The second is continuous bubble detachments from the tip of the vortex dimple. Based on CFD calculations for elemental experiments of the surface vortex, local CFD non-dimensional numbers were defined as the design criteria to prevent GE. In conclusion, it was found that the CFD non-dimensional numbers are useful for the design parameters of GE prevention.