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Journal Articles

France-Japan collaboration on severe accident studies in sodium-cooled fast reactors, 2; Methodologies and calculations of severe accident phases

Sogabe, Joji; Ishida, Shinya; Tagami, Hirotaka; Okano, Yasushi; Kamiyama, Kenji; Onoda, Yuichi; Matsuba, Kenichi; Yamano, Hidemasa; Kubo, Shigenobu; Kubota, Ryuzaburo*; et al.

Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10

In the frame of France-Japan collaboration, the calculational methodologies were defined and assessed, and the phenomenology and the severe accident consequences were investigated in a pool-type sodium-cooled fast reactor.

Journal Articles

Development of severe accident simulation code for sodium-cooled fast reactors: SIMMER-V, 1; Overview of the SIMMER-V code development

Tagami, Hirotaka; Ishida, Shinya; Okano, Yasushi; Yamano, Hidemasa; Kubo, Shigenobu; Payot, F.*; Saas, L.*; Trotignon, L.*; Gubernatis, P.*; Dufour, E.*; et al.

Proceedings of 11th European Review Meeting on Severe Accident Research Conference (ERMSAR 2024) (Internet), 12 Pages, 2024/05

JAEA has been developing the SIMMER-V code in collaboration with CEA to perform severe accident (SA) simulations of future sodium-cooled fast reactors (SFRs) including a unique core design with large-scale heterogeneous cores. An SA sequence in SFRs has been analyzed by: the SAS4A code for the Initiation Phase (IP), in which fuel pin disruption and vertical fuel dispersion occur in individual fuel subassemblies; and the two-dimensional SIMMER-III or three-dimensional SIMMER-IV code for the Transition Phase (TP), in which core disruption extends to the whole core. The joint development of SIMMER-V is of limited scope but aims at significantly expanding the code applicability by providing flexible interfaces to couple a SIMMER-V calculation with other computational domains or other codes, and by adding new advanced physical models such as a detailed fuel pin model and a model of flexible treatment of fuel isotopic composition. The former tasks are conducted by CEA the latter tasks by JAEA. In parallel to the code development, verification and validation of the new models and methods have been performed. This paper describes the objectives and overall framework of SIMMER-V code development program, representative new elements, and recent development progress.

Journal Articles

Development of severe accident simulation code for sodium-cooled fast reactors: SIMMER-V, 2; Development and verification of detailed fuel pin model

Ishida, Shinya; Tagami, Hirotaka; Okano, Yasushi; Yamano, Hidemasa; Kubo, Shigenobu; Tobita, Yoshiharu

Proceedings of 11th European Review Meeting on Severe Accident Research Conference (ERMSAR 2024) (Internet), 10 Pages, 2024/05

Journal Articles

Development and verification of detailed fuel pin model in the SIMMER-V code

Ishida, Shinya; Tagami, Hirotaka; Tobita, Yoshiharu; Okano, Yasushi; Yamano, Hidemasa; Kubo, Shigenobu

Dai-27-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 5 Pages, 2023/09

no abstracts in English

Journal Articles

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Journal Articles

Deexcitation dynamics of muonic atoms revealed by high-precision spectroscopy of electronic $$K$$ X rays

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.

Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07

 Times Cited Count:16 Percentile:77.14(Physics, Multidisciplinary)

We observed electronic $$K$$X rays emitted from muonic iron atoms using a superconducting transition-edge-type sensor microcalorimeter. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic $$K$$$$alpha$$ and $$K$$$$beta$$ X rays together with the hypersatellite $$K$$$$alpha$$ X rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the $$L$$-shell electrons, accompanied by electron side-feeding. Assisted by a simulation, this data clearly reveals the electronic $$K$$- and $$L$$-shell hole production and their temporal evolution during the muon cascade process.

Journal Articles

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

 Times Cited Count:22 Percentile:84.92(Materials Science, Multidisciplinary)

Journal Articles

Deuterium retention in tungsten coating layers irradiated with deuterium and carbon ions

Fukumoto, Masakatsu; Nakano, Tomohide; Ueda, Yoshio*; Itami, Kiyoshi; Kubo, Hirotaka

Journal of Nuclear Materials, 462, p.354 - 359, 2015/07

 Times Cited Count:4 Percentile:30.57(Materials Science, Multidisciplinary)

Journal Articles

Roles of argon seeding in energy confinement and pedestal structure in JT-60U

Urano, Hajime; Nakata, Motoki; Aiba, Nobuyuki; Kubo, Hirotaka; Honda, Mitsuru; Hayashi, Nobuhiko; Yoshida, Maiko; Kamada, Yutaka; JT-60 Team

Nuclear Fusion, 55(3), p.033010_1 - 033010_9, 2015/03

 Times Cited Count:45 Percentile:89.32(Physics, Fluids & Plasmas)

Physics picture of improving energy confinement with argon seeding at high density has been investigated in JT-60U. Better confinement is sustained at high density by argon seeding accompanied by higher core and pedestal temperatures. Peaked density profiles are kept with argon seeding. Density peaking and dilution effects lower the pedestal density at a given averaged density. The pedestal density in the argon seeded plasmas which is relatively lower than that in a single deuterium puff enables the pedestal temperature to be higher. The density peaking is a key factor of sustaining better confinement in argon seeded H-mode plasmas.

Journal Articles

Impurity, radiation, and plasma spectroscopy in divertor/SOL plasmas

Kubo, Hirotaka

Genshiryoku, Ryoshi, Kakuyugo Jiten, 1, p.196 - 197, 2014/12

Explanation about impurity, radiation, and plasma spectroscopy in divertor/SOL plasmas is presented as an article of an introductory encyclopedia on atomic power, quantum and nuclear fusion. Impurity control using divertor/SOL plasmas is essential to improve performance of fusion plasmas and prevent erosion of plasma facing components. Spatial distribution, ionization, excitation, and radiation of impurity in divertor/SOL plasmas is determined by their production, transport, and atomic processes. Here, we describe radiation loss coefficients as a brief explanation of the radiation processes and impurity flux measurement as a simple example of the plasma spectroscopy.

Journal Articles

Dismantlement of large fusion experimental device JT-60U

Ikeda, Yoshitaka; Okano, Fuminori; Sakasai, Akira; Hanada, Masaya; Akino, Noboru; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; Kubo, Hirotaka; Kobayashi, Kazuhiro; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(4), p.167 - 178, 2014/12

The JT-60U torus was disassembled so as to newly install the superconducting tokamak JT-60SA torus. The JT-60U used the deuterium for 18 years, so the disassembly project of the JT-60U was the first disassembly experience of a fusion device with radioactivation in Japan. All disassembly components were stored with recording the data such as dose rate, weight and kind of material, so as to apply the clearance level regulation in future. The lessons learned from the disassembly project indicated that the cutting technologies and storage management of disassembly components were the key factors to conduct the disassembly project in an efficient way. After completing the disassembly project, efforts have been made to analyze the data for characterizing disassembly activities, so as to contribute the estimation of manpower needs and the radioactivation of the disassembly components on other fusion devices.

Journal Articles

Safe disassembly and storage of radioactive components of JT-60U torus

Ikeda, Yoshitaka; Okano, Fuminori; Hanada, Masaya; Sakasai, Akira; Kubo, Hirotaka; Akino, Noboru; Chiba, Shinichi; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; et al.

Fusion Engineering and Design, 89(9-10), p.2018 - 2023, 2014/10

 Times Cited Count:2 Percentile:15.28(Nuclear Science & Technology)

Disassembly of the JT-60U torus was started in 2009 after 18-years D$$_{2}$$ operations, and was completed in October 2012. The JT-60U torus was featured by the complicated and welded structure against the strong electromagnetic force, and by the radioactivation due to D-D reactions. Since this work is the first experience of disassembling a large radioactive fusion device in Japan, careful disassembly activities have been made. About 13,000 components cut into pieces with measuring the dose rates were removed from the torus hall and stored safely in storage facilities by using a total wokers of 41,000 person-days during 3 years. The total weight of the disassembly components reached up to 5,400 tons. Most of the disassembly components will be treated as non-radioactive ones after the clearance verification under the Japanese regulation in future. The assembly of JT-60SA has started in January 2013 after this disassembly of JT-60U torus.

Journal Articles

Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Direct imaging of vortex polygons and vortex shells in mesoscopic squares of a weak pinning superconducting thin film

Kokubo, Nobuhito*; Okayasu, Satoru; Nojima, Tsutomu*; Tamochi, Hirotaka*; Shinozaki, Bunju*

Journal of the Physical Society of Japan, 83(8), p.083704_1 - 083704_5, 2014/08

 Times Cited Count:15 Percentile:65.73(Physics, Multidisciplinary)

Journal Articles

Magnification of a polarization angle with a Littrow layout brazed grating

Sasao, Hajime; Arakawa, Hiroyuki*; Kubo, Hirotaka; Kawano, Yasunori; Itami, Kiyoshi

Review of Scientific Instruments, 85(8), p.086106_1 - 086106_3, 2014/08

 Times Cited Count:2 Percentile:10.58(Instruments & Instrumentation)

Journal Articles

Role of seed impurity for H-mode plasmas in JT-60U

Urano, Hajime; Nakata, Motoki; Aiba, Nobuyuki; Kubo, Hirotaka; Honda, Mitsuru; Yoshida, Maiko; Hayashi, Nobuhiko; Kamada, Yutaka; JT-60 Team

Europhysics Conference Abstracts (Internet), 38F, p.P4.018_1 - P4.018_4, 2014/06

This paper reports the analysis result of heat transport and pedestal structure in H-mode plasmas with and without argon seeding on JT-60U.

Journal Articles

The Emission rates of CH, CD and C$$_{2}$$ spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates

Nakano, Tomohide; Higashijima, Satoru; Kubo, Hirotaka; Asakura, Nobuyuki; Fukumoto, Masakatsu

Nuclear Fusion, 54(4), p.043004_1 - 043004_10, 2014/03

 Times Cited Count:2 Percentile:9.67(Physics, Fluids & Plasmas)

We have determined the CH photon emission rate defined as the number of photons over dissociation and/or ionization event of $$mbox{CH}_4$$, from the ratio of the measured emission intensity of CH spectral band to the $$mbox{CH}_4$$ injection rate into the divertor plasma of JT-60U. Similar photon emission rates of CD for $$mbox{CD}_4$$, CH and $$mbox{C}_2$$ for $$mbox{C}_2mbox{H}_4$$ and $$mbox{C}_2mbox{H}_6$$ have also been determined. Interestingly, during the $$mbox{CH}_4$$ and the $$mbox{CD}_4$$ injection, the $$mbox{C}_2$$ spectral band intensity increases, suggesting that injected $$mbox{CH}_4$$ reacts with the carbon divertor plates to form heavier hydrocarbons. From the determined emission rates, previously published chemical sputtering yields, have been reevaluated. The reevaluated total chemical sputtering yield becomes lower ($$sim6%$$) compared to the original ($$sim8%$$) and the dependence on the incident ion flux and energy becomes weaker.

Journal Articles

Assembly study for JT-60SA tokamak

Shibanuma, Kiyoshi; Arai, Takashi; Hasegawa, Koichi; Hoshi, Ryo; Kamiya, Koji; Kawashima, Hisato; Kubo, Hirotaka; Masaki, Kei; Saeki, Hisashi; Sakurai, Shinji; et al.

Fusion Engineering and Design, 88(6-8), p.705 - 710, 2013/10

 Times Cited Count:11 Percentile:61.71(Nuclear Science & Technology)

Journal Articles

Contribution of Ne ions to radiation enhancement in JT-60U divertor plasmas

Nakano, Tomohide; Asakura, Nobuyuki; Kubo, Hirotaka; JT-60 Team

Journal of Nuclear Materials, 438, p.S291 - S296, 2013/07

 Times Cited Count:22 Percentile:82.87(Materials Science, Multidisciplinary)

It is already concluded that neon injection is more effective than argon injection in order to enhance the radiative power from the divertor plasmas in JT-60U. In this study, we have investigated radiation processes of neon ions in low-temperature and high-density divertor plasmas with spectroscopic technique. It was observed that the emission intensities of Ne VII spectral lines became high during plasma detachment. A collisional-radiative model analysis with the intensity ratio of Ne VII emission lines gave an electron temperature of 100 eV and a radiative power of only 5% of total radiative power, measured with a bolometer. Because C IV emission intensity was low, it is probable that the radiative power of C IV was also low. Therefore, it is possible that neon and carbon ions at other charge states contribute much to the total radiative power from the divertor plasma.

Journal Articles

Storage and safety management of radioactive components for disassembly of JT-60 tokamak device

Nishiyama, Tomokazu; Okano, Fuminori; Miyo, Yasuhiko; Kubo, Hirotaka; Miya, Naoyuki; Oikawa, Akira; Sasajima, Tadayuki; Sakasai, Akira

Heisei-22-Nendo Kumamoto Daigaku Sogo Gijutsu Kenkyukai Hokokushu (CD-ROM), 5 Pages, 2011/03

no abstracts in English

276 (Records 1-20 displayed on this page)