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Journal Articles

Numerical study on effect of pressure on behavior of bubble coalescence by using CMFD simulation

Ono, Ayako; Suzuki, Takayuki*; Yoshida, Hiroyuki

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 6 Pages, 2018/07

The mechanism of critical heat flux (CHF) for higher system pressure remains to be clarified, even though it is important to evaluate the CHF for the light water reactor (LWR) which is operated under the high pressure condition. In this study, the process of bubble coalescence was simulated by using a computational multi-fluid dynamics (CMFD) simulation code TPFIT under various system pressure in order to investigate the behavior of bubbles as a basic study. The growth of bubbles was simulated by blowing of vapor from a tiny orifice simulating bubble bottom. One or four orifices were located on the bottom surface in this simulation study. The numerical simulations were conducted by varying the pressure and temperature.

Journal Articles

Development of residual thermal stress-relieving structure of CFC monoblock target for JT-60SA divertor

Tsuru, Daigo; Sakurai, Shinji; Nakamura, Shigetoshi; Ozaki, Hidetsugu; Seki, Yohji; Yokoyama, Kenji; Suzuki, Satoshi

Fusion Engineering and Design, 98-99, p.1403 - 1406, 2015/10

 Times Cited Count:3 Percentile:32.14(Nuclear Science & Technology)

Journal Articles

Progress of ITER full tungsten divertor technology qualification in Japan

Ezato, Koichiro; Suzuki, Satoshi; Seki, Yohji; Mori, Kensuke; Yokoyama, Kenji; Escourbiac, F.*; Hirai, Takeshi*; Kuznetsov, V.*

Fusion Engineering and Design, 98-99, p.1281 - 1284, 2015/10

 Times Cited Count:28 Percentile:95.79(Nuclear Science & Technology)

Japan Atomic Energy Agency (JAEA) is now devoting to development of Full-W ITER divertor outer vertical target (OVT), especially, PFU that needs to withstand the repetitive heat load as high as 20MW/m$$^{2}$$. JAEA have succeeded in demonstrating that the soundness of a bonding technology is sufficient for the full-W ITER divertor. For the development of bonding technology, the load carrying capability test on the W monoblock with a leg attachment to an OVT support structure was carried out and shows that the attachment can withstand against the uniaxial load more than 20 kN which is three times higher than the IO requirement. JAEA manufactured 6 small-scale mock-ups and tested under the repetitive heat load of 10 and 20 MW/m$$^{2}$$ to examine the durability of the divertor structure including W tile bonding and the cooling tube. All of the mock-ups could survived 5000 cycles at 10 MW/m$$^{2}$$ and 1000 cycles 20 MW/m$$^{2}$$ with no failure such as debonding of the W tile and water leak from the cooling tube. The number of cycles at 20 MW/m$$^{2}$$ is three times longer than the requirement of ITER divertor.

Journal Articles

Experimental examination of heat removal limitation of screw cooling tube at high pressure and temperature conditions

Ezato, Koichiro; Suzuki, Satoshi; Dairaku, Masayuki; Akiba, Masato

Fusion Engineering and Design, 81(1-7), p.347 - 354, 2006/02

 Times Cited Count:10 Percentile:52.29(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Critical heat flux testing on screw cooling tube made of RAFM-steel F82H for divertor application

Ezato, Koichiro; Suzuki, Satoshi; Dairaku, Masayuki; Akiba, Masato

Fusion Engineering and Design, 75-79, p.313 - 318, 2005/11

 Times Cited Count:8 Percentile:47.08(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Study of plasma termination using high-Z noble gas puffing in the JT-60U tokamak

Bakhtiari, M.; Tamai, Hiroshi; Kawano, Yasunori; Kramer, G. J.*; Isayama, Akihiko; Nakano, Tomohide; Kamiya, Kensaku; Yoshino, Ryuji; Miura, Yukitoshi; Kusama, Yoshinori; et al.

Nuclear Fusion, 45(5), p.318 - 325, 2005/05

 Times Cited Count:41 Percentile:79.32(Physics, Fluids & Plasmas)

In the previous works we had shown that injecting a mixture of large amounts of hydrogen and small amounts of argon can terminate a tokamak discharge quickly with avoiding runaway electron generation. In this work we have done the same experiments but with different gases in addition to argon. In fact we compared the effect of the puffing of argon, krypton, and xenon gases with and without simultaneous hydrogen gas puffing on disruption mitigation. We observed that injecting all impurities in the form of an admixture in hydrogen lead to faster plasma shutdowns with less runaway electron generation. We also found that injecting krypton gas (with or without hydrogen) seems to be a good candidate for plasma shutdown purposes since it induces low heat flux to divertor plates and avoids runaway electron generation more effectively.

Journal Articles

ITER relevant high heat flux testing on plasma facing surfaces

Hirai, Takeshi*; Ezato, Koichiro; Majerus, P.*

Materials Transactions, 46(3), p.412 - 424, 2005/03

 Times Cited Count:101 Percentile:90.2(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Development of ITER divertor vertical target with annular flow concept, 2; Development of brazing technique for CFC/CuCrZr joint and heating test of large-scale mock-up

Ezato, Koichiro; Dairaku, Masayuki; Taniguchi, Masaki; Sato, Kazuyoshi; Suzuki, Satoshi; Akiba, Masato; Ibbott, C.*; Tivey, R.*

Fusion Science and Technology, 46(4), p.530 - 540, 2004/12

 Times Cited Count:14 Percentile:68.23(Nuclear Science & Technology)

The first fabrication and heating test of a large-scale CFC monoblock divertor mock-up using annular flow concept have been performed to demonstrate its manufacturability and thermo-mechanical performance. Prior to the fabrication of the mock-up, brazed joint tests between the CFC monoblock and the CuCrZr tube have been carried out to find the suitable heat treatment mitigating loss of the high mechanical strength of the CuCrZr material. Basic mechanical examination on CuCrZr undergoing the brazing heat treatment and FEM analyses are also performed to support the design of the mock-up. High heat flux tests on the large-scale divertor mock-up have been performed in an ion beam facility. The mock-up has successfully withstood more than 1,000 thermal cycles of $$rm 20 MW/m^2$$ for 15 s and 3,000 cycles more than $$rm 10 MW/m^2$$ for 15 s, which simulates the heat load condition of the ITER divertor. No degradation of the thermal performance of the mock-up has been observed throughout the thermal cycle test.

Journal Articles

Development of ITER divertor

Ezato, Koichiro

Koon Gakkai-Shi, 30(5), p.248 - 255, 2004/09

no abstracts in English

Journal Articles

Thermal fatigue experiment of screw cooling tube under one-sided heating condition

Ezato, Koichiro; Suzuki, Satoshi; Sato, Kazuyoshi; Akiba, Masato

Journal of Nuclear Materials, 329-333(1), p.820 - 824, 2004/08

 Times Cited Count:5 Percentile:36.97(Materials Science, Multidisciplinary)

This paper presents thermal fatigue experiments of a cooling tube with a helical triangular fin on its inner cooled surface, namely a ${it screw tube}$. The screw thread is directly shaped in a CuCrZr heat sink bar as a cooling channel. Slits with the width of 1.5 mm are machined at the heated side of the heat sink. The thermal fatigue experiments are carried out at 20 and 30 $$rm MW/m^2$$ by using an electron beam irradiation facility in JAERI. Water leakages from fatigue cracks, which locate at the slit of the heat sink, occurred at around 4500th and 1400th cycles at 20 and 30 $$rm MW/m^2$$, respectively. These results show good agreement with lifetime predictions using Manson-Coffin's law based on finite element analyses. Fractographic observations reveal that the fatigue cracks start from the outer heated surface at the slit region of the cooling channel and propagate toward its inner surface.

Journal Articles

Microstructural development and radiation hardening of neutron irradiated Mo-Re alloys

Nemoto, Yoshiyuki; Hasegawa, Akira*; Sato, Manabu*; Abe, Katsunori*; Hiraoka, Yutaka*

Journal of Nuclear Materials, 324(1), p.62 - 70, 2004/01

 Times Cited Count:34 Percentile:89.82(Materials Science, Multidisciplinary)

In this study, stress-relieved specimens and recrystallized specimens of pure Mo and Mo-Re alloys (Re content=2,4,5,10,13 and 41wt%) were neutron irradiated up to 20dpa at various temperatures (681-1072K). On microstructure observation, sigma phase and chi phase precipitates were observed in all irradiated Mo-Re alloys. Voids were observed in all irradiated specimen, and dislocation loops and dislocations were observed in the specimens that were irradiated at lower temperatures. On Vickers hardness testing, all of the irradiated specimens showed hardening. Especially Mo-41Re were drastically embrittled after irradiation at 874K or less. From these results, authors discuss about relation between microstructure development and radiation hardening, embrittlement, and propose the most efficient Re content and thermal treatment for Mo-Re alloys to be used under irradiation condition.

Journal Articles

Development of supercritical pressure water cooled solid breeder blanket in JAERI

Akiba, Masato; Ishitsuka, Etsuo; Enoeda, Mikio; Nishitani, Takeo; Konishi, Satoshi

Purazuma, Kaku Yugo Gakkai-Shi, 79(9), p.929 - 934, 2003/09

no abstracts in English

Journal Articles

Present research status on divertor and plasma facing components for fusion power plants

Suzuki, Satoshi; Ueda, Yoshio*; Tokunaga, Kazutoshi*; Sato, Kazuyoshi; Akiba, Masato

Fusion Science and Technology, 44(1), p.41 - 48, 2003/07

 Times Cited Count:22 Percentile:81.33(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Development of HIP technique for bonding of CuCrZr with stainless steel and beryllium for application to the ITER first wall

Hatano, Toshihisa; Enoeda, Mikio; Kuroda, Toshimasa*; Akiba, Masato

JAERI-Tech 2002-075, 59 Pages, 2002/10

JAERI-Tech-2002-075.pdf:17.38MB

no abstracts in English

Journal Articles

Wall conditioning and experience of the carbon-based first wall in JT-60U

Masaki, Kei; Yagyu, Junichi; Arai, Takashi; Kaminaga, Atsushi; Kodama, Kozo; Miya, Naoyuki; Ando, Toshiro; Hiratsuka, Hajime; Saido, Masahiro

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.386 - 395, 2002/09

 Times Cited Count:8 Percentile:49.76(Nuclear Science & Technology)

The wall conditioning of JT-60U consists of the 300$$^{circ}$$C baking, He-TDC, He-GDC, tokamak discharge cleaning and boronization. Using these methods, total pressure of the vacuum vessel reached finally 10$$^{-6}$$ $$sim$$ 10$$^{-5}$$ Pa. The oxygen impurity was decreased to $$sim$$0.5%. The experience with the carbon-based first wall showed that taper shaping is effective to reduce the local heat concentration to the tile edges. The observed poloidal asymmetric deposition of carbon on the divertor region implies that the carbon impurity produced in the outer divertor contributes to the deposition on the inner divertor. In 1992 and 1993, the B$$_{4}$$C converted CFC tiles were installed in the outer divertor to reduce chemical sputtering of CFC tiles and oxygen impurity. The reduction was successfully demonstrated with the B$$_{4}$$C converted CFC tiles. In order to understand the tritium behavior in JT-60U, tritium in the first wall and the exhaust gas were measured. The estimated tritium inventory in the first wall was $$sim$$50% of the generated tritium.

Journal Articles

Critical heat flux at high velocity channel flow with high subcooling

Sudo, Yukio; Kaminaga, Masanori

Nucl. Eng. Des., 187, p.215 - 227, 1999/00

 Times Cited Count:7 Percentile:51.01(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

DSCu/SUS joining techniques development and testing

Sato, Satoshi; Hatano, Toshihisa; Furuya, Kazuyuki; Kuroda, Toshimasa*; Enoeda, Mikio; Takatsu, Hideyuki

JAERI-Research 97-092, 80 Pages, 1998/01

JAERI-Research-97-092.pdf:5.11MB

no abstracts in English

Journal Articles

High heat flux testing of a HIP bonded first wall panel with built-in circular cooling tubes

Hatano, Toshihisa; ; ; *; *; Kitamura, Kazunori*; Kuroda, Toshimasa*; Akiba, Masato; Takatsu, Hideyuki

Fusion Engineering and Design, 39-40, p.363 - 370, 1998/00

 Times Cited Count:20 Percentile:82.55(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Development of divertor plate with CFCs bouded onto DSCu cooling tube for fusion reactor application

; *; Araki, Masanori; Nakamura, Kazuyuki; Akiba, Masato

Journal of Nuclear Materials, 258-263, p.318 - 322, 1998/00

 Times Cited Count:8 Percentile:58.55(Materials Science, Multidisciplinary)

no abstracts in English

38 (Records 1-20 displayed on this page)