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Araki, Kenji*; Suzuki, Kei*; Gubler, P.; Oka, Makoto
Physics Letters B, 780, p.48 - 53, 2018/05
Times Cited Count：3 Percentile：28.65(Astronomy & Astrophysics)Charmonium spectral functions in vector and pseudoscalar channels at finite temperature are investigated through the complex Borel sum rules and the maximum entropy method. Our approach enables us to extract the peaks corresponding to the excited charmonia, as well as those of the ground states, which has never been achieved in usual QCD sum rule analyses. We show the spectral functions in vacuum and their thermal modification around the critical temperature, which leads to the almost simultaneous melting (or peak disappearance) of the ground and excited states.
Watanabe, Kazuhito; Nakamura, Makoto; Tobita, Kenji; Someya, Yoji; Tanigawa, Hisashi; Uto, Hiroyasu; Sakamoto, Yoshiteru; Araki, Takao*; Asano, Shiro*; Asano, Kazuhito*
Proceedings of 26th IEEE Symposium on Fusion Engineering (SOFE 2015), 6 Pages, 2016/06
Safety studies of a water-cooled fusion DEMO reactor have been performed. In the event of the blanket cooling pipe break outside the vacuum vessel, i.e. ex-vacuum vessel loss of coolant accident (ex-VV LOCA), the pressurized steam and air may lead to damage reactor building walls which have confinement function, and to release the radioactive materials to the environment. In response to this accident, we proposed three cases of confinement strategies. In each case, the pressure and thermal loads to the confinement boundaries and total mass of tritium released to outside the boundaries were analyzed by accident analysis code MELCOR modified for fusion reactor. These analyses developed design parameters to maintain the integrity of the confinement boundaries.
Nakamura, Makoto; Tobita, Kenji; Gulden, W.*; Watanabe, Kazuhito*; Someya, Yoji; Tanigawa, Hisashi; Sakamoto, Yoshiteru; Araki, Takao*; Matsumiya, Hisato*; Ishii, Kyoko*; et al.
Fusion Engineering and Design, 89(9-10), p.2028 - 2032, 2014/10
Times Cited Count：13 Percentile：70.2(Nuclear Science & Technology)After the Fukushima Dai-ichi nuclear accident, a social need for assuring safety of fusion energy has grown gradually in the Japanese (JA) fusion research community. DEMO safety research has been launched as a part of BA DEMO Design Activities (BA-DDA). This paper reports progress in the fusion DEMO safety research conducted under BA-DDA. Safety requirements and evaluation guidelines have been, first of all, established based on those established in the Japanese ITER site invitation activities. The amounts of radioactive source terms and energies that can mobilize such source terms have been assessed for a reference DEMO, in which the blanket technology is based on the Japanese fusion technology R&D programme. Reference event sequences expected in DEMO have been analyzed based on the master logic diagram and functional FMEA techniques. Accident initiators of particular importance in DEMO have been selected based on the event sequence analysis.
Nakamura, Makoto; Tobita, Kenji; Someya, Yoji; Tanigawa, Hisashi; Gulden, W.*; Sakamoto, Yoshiteru; Araki, Takao*; Watanabe, Kazuhito*; Matsumiya, Hisato*; Ishii, Kyoko*; et al.
Plasma and Fusion Research (Internet), 9, p.1405139_1 - 1405139_11, 2014/10
Key aspects of the safety study of a water-cooled fusion DEMO reactor is reported. Safety requirements, dose target, DEMO plant model and confinement strategy of the safety study are briefly introduced. The internal hazard of a water-cooled DEMO, i.e. radioactive inventories, stored energies that can mobilize these inventories and accident initiators and scenarios, are evaluated. It is pointed out that the enthalpy in the first wall/blanket cooling loops, the decay heat and the energy potentially released by the Be-steam chemical reaction are of special concern for the water-cooled DEMO. An ex-vessel loss-of-coolant of the first wall/blanket cooling loop is also quantitatively analyzed. The integrity of the building against the ex-VV LOCA is discussed.
Sakamoto, Yoshiteru; Tobita, Kenji; Araki, Masanori
Journal of Plasma and Fusion Research SERIES, Vol.9, p.375 - 380, 2010/08
Recent tokamak experiments have achieved high fusion performances. Moreover, the ITER as the next step device will demonstrate the fusion burning with Q = 10, which provides the physics basis of burning plasma, including the behavior of energetic particle and the effect of self-heating towards DEMO reactors. The DEMO reactor requires not only the fusion performance but also the integrated performance. This paper summarizes the present status of the integrated performance achieved in the experiments to clarify the critical issues towards the DEMO reactor.
Araki, Masanori; Hayashi, Kimio; Tobita, Kenji; Nishitani, Takeo; Tanigawa, Hiroyasu; Nozawa, Takashi; Yamanishi, Toshihiko; Nakamichi, Masaru; Hoshino, Tsuyoshi; Ozeki, Takahisa; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 86(4), p.231 - 239, 2010/04
The Broader Approach Activities, which support the ITER Project and implement activities to aim early realization of fusion energy, is an EU-Japan collaborative project to carry out various kinds of researches and developments during the period of the ITER construction phase. In this special topic, achievements and prospects of the projects on the International Fusion Energy Research Centre (IFERC) is described.
Khan, A.*; Yamaguchi, Masafumi*; Oshita, Yoshio*; Dharmarasu, N.*; Araki, Kenji*; Abe, Takao*; Ito, Hisayoshi; Oshima, Takeshi; Imaizumi, Mitsuru*; Matsuda, Sumio*
Journal of Applied Physics, 90(3), p.1170 - 1178, 2001/08
Times Cited Count：56 Percentile：86.43(Physics, Applied)1MeV-electron and 10MeV-proton irradiations into Si doped various impurities such as B, Ga, O and C were performed and residual defects in the Si were studied using DLTS and C-V measurements.It was revealed that Ci-Oi whose level is Ev-0.36 eV and Bi-Oi whose energy is Ec-0.18eV were generated. In Ga-doped Si, the generation of Ci-Oi was suppressed. Since Ci-Oi acts as scattering center, this result indicates that the radiation resistance of solar cells is improved by using Ga-doped Si substrates.Furthermore, a new defect level (Ev+18eV) was observed in Ga-dpoed Si by irradiation. This defect level was annealed out above 350 C.
Kuriyama, Masaaki; ; Araki, Masanori; ; Hanada, Masaya; Inoue, Takashi; Kawai, Mikito; Kazawa, Minoru; *; Kunieda, Shunsuke; et al.
Fusion Engineering and Design, 26, p.445 - 453, 1995/00
Times Cited Count：43 Percentile：95.65(Nuclear Science & Technology)no abstracts in English
Suzuki, Satoshi; Akiba, Masato; Araki, Masanori; Sato, Kazuyoshi; Yokoyama, Kenji; Dairaku, Masayuki
Journal of Nuclear Materials, 212-215(1), p.1365 - 1369, 1994/09
no abstracts in English
Ushigusa, Kenkichi; Imai, Tsuyoshi; Ikeda, Yoshitaka; Sakamoto, Keishi; F.X.Soeldner*; *; Tsuji, Shunji; Shimizu, Katsuhiro; Naito, Osamu; Uehara, Kazuya; et al.
Nuclear Fusion, 29(2), p.265 - 276, 1989/02
Times Cited Count：17 Percentile：58.82(Physics, Fluids & Plasmas)no abstracts in English
Ushigusa, Kenkichi; Imai, Tsuyoshi; Ikeda, Yoshitaka; Sakamoto, Keishi; F.X.Soldner*; *; Tsuji, Shunji; Shimizu, Katsuhiro; Naito, Osamu; Uehara, Kazuya; et al.
JAERI-M 88-115, 28 Pages, 1988/06
no abstracts in English
Tobita, Kenji; Nishio, Satoshi; Nishitani, Takeo; Ozeki, Takahisa; Araki, Masanori; Okano, Kunihiko*; Hiwatari, Ryoji*; Ogawa, Yuichi*
no journal, ,
During the first three years of BA DEMO design activity, exchange of opinions is carried out between Japanese and European experts in a workshop style. In the previous two workshops, the both parties were devoted to discussions on definition of DEMO, role of DEMO in their fusion development program, requirements for DEMO and issues on DEMO physics and engineering. Throughout the discussion, common design issues which are not independent DEMO design concepts, including (1) divertor, (2) maintenance, (3) superconducting magnet, (4)current drive (steady state operation), etc. Key issues regarding each subject are removal of high heat load in the divertor under severe neutron environment, maintenance scheme which could provide high availability, need for high field superconducting magnet, and current drive schemes favorable in the aspects of the current drive efficiency and the controllability of current profile.
Sakamoto, Yoshiteru; Araki, Masanori; Tobita, Kenji; Lorenzo, S.*; Maisonnier, D.*
no journal, ,
BA DEMO Design Activity is one of the sub-projects on the Project on the International Fusion Energy Research Centre (IFERC Project). Objectives of BA DEMO design activity are aiming at establishing a common basis for a DEMO design, including: (1) holding of seminars and other meetings; (2) provision and exchange of scientific and technical information; and (3) DEMO conceptual design activities. Taking into account of the present divergence in the DEMO concepts, the activity consist of at least the two phases. In the Phase One until the middle of 2010, the activity is mainly done by workshops, which are focused on assessment of the DEMO design basis and definition of critical issues for DEMO design. In the Phase Two, joint work will be organised at Rokkasho to develop potential conceptual DEMO design. This presentation will report summary of Phase One activity and the tentative plans of Phase Two.
Nakamura, Makoto; Tobita, Kenji; Someya, Yoji; Tanigawa, Hisashi; Araki, Takao*; Watanabe, Kazuhito*; Kittaka, Daigo*; Ishii, Kyoko*; Matsumiya, Hisato*
no journal, ,
Recent findings on safety characteristics of a tokamak DEMO reactor are reported in the case where all the coolant water is lost completely and instantaneously. Assuming that there are neither off-site power nor active emergency cooling, we have analyzed temporal histories of the temperatures of the reactor components using the fusion reactor thermo-hydraulic analysis code MELCOR-fus. We have found that even in such an extremely severe case, the temperatures of the vacuum vessel and in-vessel components do not reach their melting points.
