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110 results on '"Oyaidzu, M."'

1. Overview of tritium retention in divertor tiles and dust particles from the JET tokamak with the ITER-like wall

Author

Torikai, Y., Kikuchi, G., Owada, A., Masuzaki, S., Otsuka, T., Ashikawa, N., Yajima, M., Tokitani, M., Oya, Y., Lee, S. E., Hatano, Y., Asakura, N., Hayashi, T., Oyaidzu, M., Likonen, J., Widdowson, A., Rubel, Marek, Torikai, Y., Kikuchi, G., Owada, A., Masuzaki, S., Otsuka, T., Ashikawa, N., Yajima, M., Tokitani, M., Oya, Y., Lee, S. E., Hatano, Y., Asakura, N., Hayashi, T., Oyaidzu, M., Likonen, J., Widdowson, A., and Rubel, Marek

Abstract

Divertor tiles after Joint European Torus-ITER like wall (JET-ILW) campaigns and dust collected after JET-C and JET-ILW operation were examined by a set of complementary techniques (full combustion and radiography) to determine the total, specific and areal tritium activities, poloidal tritium distribution in the divertor and the presence of that isotope in individual dust particles. In the divertor tiles, the majority of tritium is detected in the surface region and, the areal activities in the ILW divertor are in the 0.5-12 kBq cm-2 range. The activity in the ILW dust is associated mainly with the presence of carbon particles being a legacy from the JET-C operation. The total tritium activities show significant differences between the JET operation with ILW and the earlier phase with the carbon wall (JET-C) indicating that tritium retention has been significantly decreased in the operation with ILW.

Published
2024
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9. R&D Activities for Fusion DEMO in the QST Rokkasho Fusion Institute

Author

Ishii, Y., primary, Aiba, N., additional, Ando, M., additional, Asakura, N., additional, Bierwage, A., additional, Cara, P., additional, Dzitko, H., additional, Edao, Y., additional, Gex, D., additional, Hasegawa, K., additional, Hayashi, T., additional, Hiwatari, R., additional, Hoshino, T., additional, Ikeda, Y., additional, Ishida, S., additional, Isobe, K., additional, Iwai, Y., additional, Jokinen, A., additional, Kasugai, A., additional, Kawamura, Y., additional, Kim, J. H., additional, Kondo, K., additional, Kwon, S., additional, Lorenzo, S. C., additional, Masuda, K., additional, Matsuyama, A., additional, Miyato, N., additional, Morishita, K., additional, Nakajima, M., additional, Nakajima, N., additional, Nakamichi, M., additional, Nozawa, T., additional, Ochiai, K., additional, Ohta, M., additional, Oyaidzu, M., additional, Ozeki, T., additional, Sakamoto, K., additional, Sakamoto, Y., additional, Sato, S., additional, Seto, H., additional, Shiroto, T., additional, Someya, Y., additional, Sugimoto, M., additional, Tanigawa, H., additional, Tokunaga, S., additional, Utoh, H., additional, Wang, W., additional, Watanabe, Y., additional, and Yagi, M., additional

Published
2021
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13. Surface morphology of the bulk tungsten divertor tiles from JET ITER-like wall

Author

Tokitani, M., Miyamoto, M., Masuzaki, S., Hatano, Y., Lee, S. E., Oya, Y., Otsuka, T., Oyaidzu, M., Kurotaki, H., Suzuki, T., Hamaguchi, D., Hayashi, T., Asakura, N., Widdowson, A., Jachmich, S., Rubel, Marek, Tokitani, M., Miyamoto, M., Masuzaki, S., Hatano, Y., Lee, S. E., Oya, Y., Otsuka, T., Oyaidzu, M., Kurotaki, H., Suzuki, T., Hamaguchi, D., Hayashi, T., Asakura, N., Widdowson, A., Jachmich, S., and Rubel, Marek

Abstract

Surface characterization of bulk tungsten tiles (W lamellae) used during the first campaign of JET with the ITER-Like Wall (JET-ILW) was performed by means of microscopy and tritium imaging techniques. This is the first report regarding very detailed structural studies of W lamellae from the JET-ILW divertor. A special feature of the W lamellae installed in JET is the intrinsic network of micro-cracks detected on surfaces of the as-manufactured material. Analyses of different W lamellae samples on the plasma-facing surface reveal two types of surface structures caused by plasma impact: areas with strong erosion and regions of mild plasma interaction. In regions of strong erosion, a thin modified layer (thickness of similar to 20 nm) with a high density of defects including bubble-like structures has been formed. In addition, features indicating melting along edges of micro-cracks with the micro-scale plastic deformation have been identified., QC 20200414

Published
2020
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16. Conceptual design progress of advanced fusion neutron source

Author

Ochiai, K., primary, Sato, S., additional, Kondo, H., additional, Ohta, M., additional, Oyaidzu, M., additional, Nakamura, M.M., additional, Kwon, S., additional, Tanigawa, H., additional, Nozawa, T., additional, Kasugai, A., additional, Sakamoto, K., additional, and Ishida, S., additional

Published
2020
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30. Conceptual design progress of advanced fusion neutron source.

Author

Ochiai, K., Sato, S., Kondo, H., Ohta, M., Oyaidzu, M., Nakamura, M.M., Kwon, S., Tanigawa, H., Nozawa, T., Kasugai, A., Sakamoto, K., and Ishida, S.

Subjects
TRITIUM, CONCEPTUAL design, NEUTRON sources, FUSION reactor blankets, TESTING laboratories, FUSION reactors, IRRADIATION
Abstract

Based on the results of the IFMIF/EVEDA project in the broader approach (BA) activities, the conceptual design of the Advanced Fusion Neutron Source (A-FNS) to obtain irradiation data of DEMO blanket materials is under consideration in Japan. This paper describes the progress of the A-FNS conceptual design, which consists of a 40 MeV, 125 mA deuteron beam, a liquid lithium target system, and a test and post-irradiation test facilities. the main objectives of the A-FNS are the acquisition of RAFM irradiation data up to 2035 and the tritium recovery test on the blanket. In addition, it is expected to be used for various neutron researches. The technical design activities of the A-FNS are focused on improvement of the lithium target design, review of impurity criteria, remote handling, and irradiation application plan. [ABSTRACT FROM AUTHOR]

Published
2021
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31. Dust generation in tokamaks : Overview of beryllium and tungsten dust characterisation in JET with the ITER-like wall

Author

Rubel, Marek, Widdowson, A., Grzonka, J., Fortuna-Zalesna, E., Moon, Sunwoo, Petersson, Per, Ashikawa, N., Asakura, N., Hamaguchi, D., Hatano, Y., Isobe, K., Masuzaki, S., Kurotaki, H., Oya, Y., Oyaidzu, M., Tokitani, M., Rubel, Marek, Widdowson, A., Grzonka, J., Fortuna-Zalesna, E., Moon, Sunwoo, Petersson, Per, Ashikawa, N., Asakura, N., Hamaguchi, D., Hatano, Y., Isobe, K., Masuzaki, S., Kurotaki, H., Oya, Y., Oyaidzu, M., and Tokitani, M.

Abstract

Operation of the JET tokamak with beryllium and tungsten ITER-like wall provides unique opportunity for detailed studies on dust generation: quantity, morphology, location, etc. The programme carried out in response to ITER needs for safety assessment comprises: (i) remotely controlled vacuum cleaning of the divertor; (ii) local sampling of loosely bound matter from plasma-facing components (PFC); (iii) collection of mobilized dust on various erosion-deposition probes located in the divertor and in the main chamber. Results of comprehensive analyses performed by a number of complementary techniques, e.g. a range of microscopy methods, electron and ion spectroscopy, liquid scintillography and thermal desorption, are summarized by following points: (a) Total amount of dust collected by vacuum cleaning after three campaigns is about 1-1.4 g per campaign (19.1-23.5 h plasma operation), i.e. over 100 times smaller than in JET operated with carbon walls (i.e. in JET-C). (b) Two major categories of Be dust are identified: flakes of co-deposits formed on PFC and droplets (2-10 mu m in diameter). Small quantifies, below 1 g, of Be droplets and splashes are associated mainly with melting of beryllium limiters., QC 20190109

Published
2018
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32. Correlation of surface chemical states with hydrogen isotope retention in divertor tiles of JET with ITER-Like Wall

Author

Oya, Y., Masuzaki, S., Tokitani, M., Azuma, K., Oyaidzu, M., Isobe, K., Asakura, N., Widdowson, A. M., Heinola, K., Jachmich, S., Rubel, Marek, Contributors, JET, Oya, Y., Masuzaki, S., Tokitani, M., Azuma, K., Oyaidzu, M., Isobe, K., Asakura, N., Widdowson, A. M., Heinola, K., Jachmich, S., Rubel, Marek, and Contributors, JET

Abstract

To understand the fuel retention mechanism correlation of surface chemical states and hydrogen isotope retention behavior determined by XPS (X-ray photoelectron spectroscopy) and TDS (Thermal desorption spectroscopy), respectively, for JET ITER-Like Wall samples from operational period 2011–2012 were investigated. It was found that the deposition layer was formed on the upper part of the inner vertical divertor area. At the inner plasma strike point region, the original surface materials, W or Mo, were found, indicating to an erosion-dominated region, but deposition of impurities was also found. Higher heat load would induce the formation of metal carbide. At the outer horizontal divertor tile, mixed material layer was formed with iron as an impurity. TDS showed the H and D desorption behavior and the major D desorption temperature for the upper part of the inner vertical tile was located at 370 °C and 530 °C. At the strike point region, the D desorption temperature was clearly shifted toward higher release temperatures, indicating the stabilization of D trapping by higher heat load., QC 20180529

Published
2018
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39. Tritium Retention in Reduced-Activation Ferritic/Martensitic Steels

Author

Hatano, Y., primary, Alimov, V. Kh., additional, Spitsyn, A. V., additional, Bobyr, N. P., additional, Cherkez, D. I., additional, Abe, S., additional, Ogorodnikova, O. V., additional, Klimov, N. S., additional, Khripunov, B. I., additional, Golubeva, A. V., additional, Chernov, V. M., additional, Oyaidzu, M., additional, Yamanishi, T., additional, and Matsuyama, M., additional

Published
2015
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48. Retention of Hydrogen Isotopes in Divertor Tiles Used in JT-60U

Author

Hirohata, Y., primary, Shibahara, T., additional, Tanabe, T., additional, Oya, Y., additional, Arai, T., additional, Gotoh, Y., additional, Masaki, K., additional, Yagyu, J., additional, Oyaidzu, M., additional, Okuno, K., additional, Nishikawa, M., additional, and Miya, N., additional

Published
2005
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49. Tritium Trapping on the Plasma Irradiated Tungsten Surface

Author

Torikai, Y., Alimov, V. Kh., Isobe, K., Oyaidzu, M., Yamanishi, T., Penzhorn, R.-D., Ueda, Y., Kurishita, H., Philipps, V., Kreter, A., and Zlobinski, M.

Abstract

AbstractTungsten (W) specimens previously exposed to deuterium (D) plasmas both in the TEXTOR tokamak and high flux linear plasma generator (LPG) were subsequently loaded with tritium at 573 K for 3 h. Retention of tritium in the near-surface W layer was examined by imaging plate technique. On the TEXTOR-plasma-exposed W surface, tritium was mainly trapped in carbon deposits. For LPG-plasma-exposed W specimens, tritium was trapped in defects created in the near-surface layer during the course of D plasma exposure.

Published
2015
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50. Hot atom chemical behavior of tritium in neutron-irradiated Li2TiO3 and Li2ZrO3.

Author

Oyaidzu, M., Yoshikawa, A., Nishikawa, Y., Munakata, K., Nishikawa, M., and Okuno, K.

Subjects
*TRITIUM, *HYDROGEN isotopes, *PARTICLES (Nuclear physics), *NEUTRON irradiation, *NUCLEAR reactions, *PHYSICAL & theoretical chemistry
Abstract

The annihilation behavior of irradiation defects induced in neutron-irradiated Li2TiO3 and Li2ZrO3 were investigated with the tritium release behavior. It was revealed that the common characteristics in both samples were that the annihilation process of irradiation defects consisted of two first-order processes and E’-center could act as tritium trapping site, and otherwise was the way how the E’-center annihilated. The difference was suggested to attribute to the mobility of M as M4+ (or M3+, etc.). [ABSTRACT FROM AUTHOR]

Published
2007
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