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Journal Articles

Forced convection heat transfer of subcooled liquid nitrogen in horizontal tube

Tatsumoto, Hideki; Shirai, Yasuyuki*; Hata, Koichi*; Kato, Takashi; Shiotsu, Masahiro*

AIP Conference Proceedings 985, p.665 - 672, 2008/03

The knowledge of forced convection heat transfer of liquid hydrogen is important for the cooling design of a material of a cold neutron moderator. An experimental apparatus that obtain forced flow without a pump was developed. As a first step of the study, the forced flow heat transfer of subcooled liquid nitrogen in a horizontal tube, instead of liquid hydrogen, was measured for the pressures (0.3 to 2.5 MPa). The inlet temperature was varied from 78 K to around its saturation temperature. The flow velocity was varied from 0.1 to 7 m/s. The heat transfer coefficients in non boiling region and the DNB heat fluxes were higher for higher flow velocity and higher subcooling. The measured values of Nu/Pr$$^{0.4}$$ in non-boiling region were proportional to Re to the power of 0.8. With decrease in Re, they approached a constant value corresponding to that in a pool of liquid nitrogen. The correlation of DNB derived here can describe the experimental data within 15% difference was derived.

Journal Articles

Thermal stress analysis for a transfer line of hydrogen moderator in J-PARC

Tatsumoto, Hideki; Teshigawara, Makoto; Aso, Tomokazu; Otsu, Kiichi; Maekawa, Fujio; Kato, Takashi

AIP Conference Proceedings 985, p.1225 - 1232, 2008/03

In JSNS, cryogenic hydrogen at supercritical pressure is selected as a moderator material. Three kinds of hydrogen moderator are installed to provide higher neutronic performance. The transfer lines around the moderators should be changed every 6 years due to its radiation damage. The detachment of the transfer line will be only performed by a hands-on. Therefore, minimum pipe size and elbow-type bend sections are installed to reduce the radiation dose by the radiation streaming. Some spacers are installed so as to avoid touching the hydrogen pipe to the outer vacuum pipe due to thermal shrinkage. In the design, we should consider mechanical stress concentration, deformation, and, touching between the pipes due to the thermal shrinkage at the cryogenic hydrogen temperature. The appropriate locations of spacers to keep the thermal stress below an allowable stress and to avoid touching between the pipes were determined.

Journal Articles

The JT-60SA cryoplant current design status

Henry, D.*; Michel, F.*; Roussel, P.*; Reynaud, P.*; Journeaux, J. Y.*; Mar$'e$chal, J. L.*; Balaguer, D.*; Roux, C.*; Matsukawa, Makoto; Yoshida, Kiyoshi

AIP Conference Proceedings 985, p.445 - 452, 2008/03

 Times Cited Count:0 Percentile:0.07

In the framework of the ITER Broader Approach, CEA is carrying out the procurement of the Cryogenic System to the JA-EU Satellite Tokamak JT-60SA, which should be operated in Japan at JAEA, Naka in 2014. According to the Conceptual Design Report, JT-60SA is to operate for periods of at least 6 months per year, with major shutdown periods in between for maintenance and further installation upgrades. For this operation scenario, the cryoplant and the cryodistribution have to cope with different heat loads which depend on the different JT-60SA operating states. The cryoplant consists of one 4.5 K refrigerator and one 80 K helium loop, each pre-cooled by LN2. These cryogenic subsystems have to operate simultaneously in order to remove the heat loads from the superconducting magnets, 80 K shields and the divertor cryopumps. The first part of this study is based on the Process Flow Diagram (PFD) and presents the current design status of the JT-60SA cryogenic system. The second part is dedicated to the analysis of the cryoplant normal operation modes including the regeneration mode of the divertor cryopumps.

Journal Articles

Development of jacketing technologies for ITER CS and TF conductor

Hamada, Kazuya; Nakajima, Hideo; Matsui, Kunihiro; Kawano, Katsumi; Takano, Katsutoshi; Tsutsumi, Fumiaki; Okuno, Kiyoshi; Teshima, Osamu*; Soejima, Koji*

AIP Conference Proceedings 986, p.76 - 83, 2008/03

The ITER Toroidal Field (TF) coil and Central Solenoid (CS) use Nb$$_{3}$$Sn cable-in-conduit conductor. Conductor fabrication process are as follows; (1) Fabrication of jacket. (2) Butt welding of jacket to make a long tube (CS: 880 m, TF: 760 m) and insertion of superconducting cable into jacket. (3) Compaction of jacket. (4) Winding for transportation. JAEA has developed jacketing technologies in the cooperation with industries. Major achievements are as follows; (1) Full scale TF and CS jackets were fabricated using low carbon SUS316LN and boron added and high manganese stainless steel (JK2LB), respectively. The jackets satisfied ITER mechanical and dimensional requirement. (2) Butt welding condition was studied to obtain good internal surface condition of welded joint. (3) Compaction machine was constructed. As results of compaction test of TF and CS jacket, compacted jacket dimensions satisfied ITER requirement. Therefore, JAEA demonstrated jacketing technologies for ITER conductor.

Journal Articles

Gas evolution from insulating materials for superconducting coil of ITER by gamma ray irradiation at liquid nitrogen temperature

Idesaki, Akira; Koizumi, Norikiyo; Sugimoto, Makoto; Morishita, Norio; Oshima, Takeshi; Okuno, Kiyoshi

AIP Conference Proceedings 986, p.169 - 173, 2008/03

A laminated material composed of glass cloth/polyimide film/epoxy resin will be used as an insulating material for superconducting coil of ITER. In order to keep safe and stable operation of the superconducting coil system, it is indispensable to evaluate radiation resistance of the material, because the material is exposed to high radiation field of 10 MGy at low temperature of 4 K. In this work, the gas evolution from the laminated material by gamma ray irradiation at liquid nitrogen temperature (77 K) was investigated, and the difference of gas evolution behavior due to difference of components in the epoxy resin was discussed. As a result, it was found that the main gases from the epoxy resin by the irradiation were hydrogen, carbon monoxide and carbon dioxide, and that the amount of the gases from epoxy resin containing cyanate ester was 30-40% less than that from the epoxy resin containing tetraglycidyl-diaminophenylmethane (TGDDM).

Oral presentation

Cryogenic structural materials for the ITER superconducting magnets

Okuno, Kiyoshi; Nakajima, Hideo; Hamada, Kazuya; Kawano, Katsumi; Takano, Katsutoshi; Tsutsumi, Fumiaki

no journal, , 

The ITER superconducting magnet system consists of 18 Toroidal Field (TF) coils, one Central Solenoid (CS) and six Poloidal Field (PF) coils. The TF coil has a D-shape with a height of 14 m, a width of 9 m and a weight of 310 tons. In order to sustain large electromagnetic forces, the TF coil has a massive coil case that contains a winding pack The total weight of stainless steel required for the 19 TF coils (18 + one spare) amounts to 3,800 tons in finished shape, which corresponds to more than 10,000 tons in raw materials. Trial fabrications of the TF structures are underway at full scale in extensive collaboration with industries. Complete database on mechanical properties of these materials is being established. Technologies for the machining and welding of these materials into coil case segments are also under development and successful results have so-far been obtained.

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