Manufacture of substitutive assemblies for MONJU reactor decommissioning

Sakakibara, Hiroshi; Aoki, Nobuhiro; Muto, Masahiro; Otabe, Jun; Takahashi, Kenji*; Fujita, Naoyuki*; Hiyama, Kazuhiko*; Suzuki, Hirokazu*; Kamogawa, Toshiyuki*; Yokosuka, Toru*; et al.

JAEA-Technology 2020-020, 73 Pages, 2021/03

JAEA-Technology-2020-020.pdf:8.26MB

The decommissioning is currently in progress at the prototype fast breeder reactor Monju. Fuel assemblies will be taken out of its core for the first step of the great task. Fuel assemblies stand on their own spike plugged into a socket on the core support plate and support with adjacent assemblies through their housing pads each other, resulting in steady core structure. For this reason, some substitutive assemblies are necessary for the purpose of discharging the fuel assemblies of the core. Monju side commissioned, therefore, Plutonium Fuel Development Center to manufacture the substitutive assemblies and the Center accepted it. This report gives descriptions of design, manufacture, and shipment in regard to the substitutive assemblies.

Dependence of heat transport and confinement on isotopic composition in conventional H-mode plasmas in JT-60U

Urano, Hajime; Takizuka, Tomonori*; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/01

http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/188_EX24.pdf

Dependence of heat transport on isotopic composition is investigated in conventional H-mode plasmas for the application to ITER. The identical profiles of , and are obtained for hydrogen and deuterium plasmas while the required power becomes clearly larger for hydrogen, resulting in the reduction of the heat diffusivity for deuterium. The result of the identical temperature profiles in spite of different heating power suggests that the characteristics of heat conduction differs essentially between hydrogen and deuterium even at the same scale length of temperature gradient. On the other hand, the edge stability is improved by increased total regardless of the difference of the isotropic composition.

The Unified effect of counter-toroidal rotation and power across separatrix on type-I ELMs in JT-60U

Urano, Hajime; Oyama, Naoyuki; Kamiya, Kensaku; Aiba, Nobuyuki; Kamada, Yutaka; Fujita, Takaaki; JT-60 Team

Nuclear Fusion, 52(10), p.103012_1 - 103012_7, 2012/10

https://doi.org/10.1088/0029-5515/52/10/103012

The unified effect of counter toroidal rotation and heating power on type-I ELMs was investigated in JT-60U tokamak. ELM frequency increased monotonically together with the power across the sepratrix for all the cases of tangential NBs. However, dependence of on was explicitly stronger than a proportional relation when the perpendicular NBs were injected. The toroidal rotation velocity at the H-mode pedestal shifted continuously in counter direction when the perpendicular NBs were applied. At fixed values of , increased clearly in proportion to .

Development of function-graded proton exchange membrane for PEFC using heavy ion beam irradiation

Shiraki, Fumiya*; Yoshikawa, Taeko*; Oshima, Akihiro*; Oshima, Yuji*; Takasawa, Yuya*; Fukutake, Naoyuki*; Oyama, Tomoko*; Urakawa, Tatsuya*; Fujita, Hajime*; Takahashi, Tomohiro*; et al.

Nuclear Instruments and Methods in Physics Research B, 269(15), p.1777 - 1781, 2011/08

https://doi.org/10.1016/j.nimb.2011.04.117

The graded energy deposition of heavy ion beam irradiation to polymeric materials was utilized to synthesize a novel proton exchange membrane (PEM) with the graded density of sulfonic acid groups toward the thickness direction. Stacked Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films were irradiated by Xe ion beam with the energy of 6 MeV/u under a vacuum condition. Irradiated films were grafted with styrene monomer and then sulfonated. The membrane electrode assembly (MEA) fabricated by the function graded PEM showed improved fuel cell performance in terms of voltage stability. It was expected that the function-graded PEM could control the graded concentration of sulfonic acid groups in PEM.

Measurement of type-I ELM pulse propagation in SOL through BES use of MSE diagnostics in JT-60U and impact of ELM on MSE diagnostics

Suzuki, Takahiro; Oyama, Naoyuki; Asakura, Nobuyuki; Fujita, Takaaki

Proceedings of 37th European Physical Society Conference on Plasma Physics (EPS 2010) (CD-ROM), 4 Pages, 2010/06

http://ocs.ciemat.es/EPS2010PAP/pdf/D4.516.pdf

Since transient heat and particle loads by the type-I ELMs are significantly high for the plasma facing components of the fusion reactor, understanding propagation of plasma ejected by ELMs (ELM pulse) in SOL is important. Increase in the SOL plasma density due to the ELM pulse has been measured through the increase in beam emission (BE) at various radial locations in SOL near equatorial plane, using MSE diagnostics as beam emission spectroscopy (BES) diagnostics. From the temporal delay of the increase of BE as a function of major radius in the SOL, radial velocity of the ELM pulse propagation has been evaluated as 0.8-1.8 km/s. In accurately evaluating the velocity, elimination of background (BG) light from the BES signal is found essential since the delay of the net BE is veiled by the BG light that increases in synchronous to the ELM pulse. The intermittent increase in the BG light synchronized with ELMs has been observed in MSE channels viewing not only the SOL but also the main plasma. Since this BG light affects the magnetic pitch angle measurement by MSE diagnostics as was reported in JET, the impact of the intermittent BG light by ELMs on MSE diagnostics has been investigated numerically. When intermittent BG light by ELMs mixes with PEM modulation for MSE diagnostics, broadband spectrum of the impulse-like BG light disturbs the spectrum intensities, even if the BG light is not polarized. Numerical simulation shows that error induced by ELMs piles up if ELM frequency is higher than , where is time constant of lock-in amplifier detecting PEM modulation, and then, the error remains even between ELMs.

Fast dynamics of type I and grassy ELMs in JT-60U

Kojima, Atsushi; Oyama, Naoyuki; Sakamoto, Yoshiteru; Kamada, Yutaka; Urano, Hajime; Kamiya, Kensaku; Fujita, Takaaki; Kubo, Hirotaka; Aiba, Nobuyuki; JT-60 Team

Nuclear Fusion, 49(11), p.115008_1 - 115008_8, 2009/11

https://doi.org/10.1088/0029-5515/49/11/115008

In order to understand the physics of the ELM trigger and determining the ELM size, the fast ELM dynamics of type I and grassy ELMs have been studied in JT-60U, using new fast diagnostics with high spatial and temporal resolutions. The evolution of the ion pressure profile in the pedestal region is evaluated for the first time by detailed edge profile measurements. Type I ELMs observed in co-rotating plasmas exhibited larger and wider ELM affected area than ctr-rotating plasmas. Just before type I ELM crash, the pedestal ion pressure and its maximum gradient in co-rotating plasmas are 20% and 12% higher than those in ctr-rotating plasmas, respectively. It is found that the radial extent of the ion pressure gradient at the pedestal region in co-rotating plasmas is 14% wider than that in ctr-rotating plasmas. The experimental results suggest that the ELM size is determined by the structure of the plasma pressure in the whole pedestal region.

The Impact of the current density profile on heat transport and pedestal structure in JT-60U

Urano, Hajime; Sakamoto, Yoshiteru; Suzuki, Takahiro; Fujita, Takaaki; Kamiya, Kensaku; Isayama, Akihiko; Kamada, Yutaka; Takenaga, Hidenobu; Oyama, Naoyuki; Matsunaga, Go; et al.

Nuclear Fusion, 49(9), p.095006_1 - 095006_7, 2009/09

https://doi.org/10.1088/0029-5515/49/9/095006

H-modes operated at higher with the current ramp down have shown higher energy confinement with higher density in JT-60U. The -factor evaluated for the core plasma depends strongly on with the relation of for the case without sawtooth activities. Center peaked profiles of electron density and electron temperature are obtained in high H-modes. The pedestal pressure is not significantly changed. The enhanced energy confinement in high H-modes is attributed to the core improvement with the peaked profiles of electron density and temperature. The electron heat diffusivity is reduced at the plasma core in high case, resulting in the center peaked profile while the profiles are approximately unchanged.

Dynamics of ion internal transport barrier in LHD heliotron and JT-60U tokamak plasmas

Ida, Katsumi*; Sakamoto, Yoshiteru; Yoshinuma, Mikiro*; Takenaga, Hidenobu; Nagaoka, Kenichi*; Hayashi, Nobuhiko; Oyama, Naoyuki; Osakabe, Masaki*; Yokoyama, Masayuki*; Funaba, Hisamichi*; et al.

Nuclear Fusion, 49(9), p.095024_1 - 095024_9, 2009/09

https://doi.org/10.1088/0029-5515/49/9/095024

Dynamics of ion internal transport barrier (ITB) formation and impurity transport both in the Large Helical Device (LHD) heliotron and JT-60U tokamak are described. Significant differences between heliotron and tokamak plasmas are observed. The location of the ITB moves outward during the ITB formation regardless of the sign of magnetic shear in JT-60U and the ITB becomes more localized in the plasma with negative magnetic shear. In LHD, the low Te/Ti ratio ( 1) of the target plasma for the high power heating is found to be necessary condition to achieve the ITB plasma and the ITB location tends to expand outward or inward depending on the condition of the target plasmas. Associated with the formation of ITB, the carbon density tends to be peaked due to inward convection in JT-60U, while the carbon density becomes hollow due to outward convection in LHD. The outward convection observed in LHD contradicts the prediction by neoclassical theory.

Status of JT-60SA tokamak under the EU-JA broader approach agreement

Matsukawa, Makoto; Kikuchi, Mitsuru; Fujii, Tsuneyuki; Fujita, Takaaki; Hayashi, Takao; Higashijima, Satoru; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Ide, Shunsuke; Ishida, Shinichi; et al.

Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12

https://doi.org/10.1016/j.fusengdes.2008.06.047

no abstracts in English

Heat transport and pedestal structure of H-mode in the variation of current density profiles in JT-60U

Urano, Hajime; Sakamoto, Yoshiteru; Suzuki, Takahiro; Fujita, Takaaki; Kamiya, Kensaku; Isayama, Akihiko; Kamada, Yutaka; Takenaga, Hidenobu; Oyama, Naoyuki; Matsunaga, Go; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

http://www-naweb.iaea.org/napc/physics/FEC/FEC2008/html/node477.htm#95259

Dependence of the H-mode confinement and pedestal structure on the plasma current is investigated. Higher energy confinement is obtained in higher H-mode. The profiles of the core and are tends to be peaked. The H-factor for the core plasma depends strongly on . Higher energy confinement obtained at higher is attributed to the core confinement improvement. The edge pedestal pressure is not significantly changed by core current density profile. In both ramp and scan experiments, the core energy confinement is improved by the increased core value. The effect of magnetic shear on the confinement should be investigated in next step study.