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Sakasegawa, Hideo; Nakajima, Motoki*; Kato, Taichiro*; Nozawa, Takashi*; Ando, Masami*
Materials Today Communications (Internet), 40, p.109659_1 - 109659_8, 2024/08
Times Cited Count：1 Percentile：7.27(Materials Science, Multidisciplinary)Nanometric oxide particles play an important role in improving the creep property of Oxide Dispersion Strengthened (ODS) steels. In our previous research, we examined a microstructural feature known as prior particle boundary (PPB). PPB refers to the surface of mechanically alloyed (MA) powders before consolidation. We revealed that the ODS steel with fine PPBs produced from smaller MA powders, exhibited shorter creep rupture times, compared to that with coarse PPBs produced from larger MA powders. The size of MA powders had an impact on the creep property. In this study, we examined the shape of MA powders, which were non-spherical shapes. Such shapes have the potential to induce anisotropic creep behavior. We conducted small punch creep tests on specimens with two different orientations to study the possible anisotropy. The results revealed that the creep rupture times varied depending on the orientation of specimen, thus indicating anisotropic creep property.
Teshigawara, Makoto; Tsuchikawa, Yusuke*; Ichikawa, Go*; Takata, Shinichi; Mishima, Kenji*; Harada, Masahide; Oi, Motoki; Kawamura, Yukihiko*; Kai, Tetsuya; Kawamura, Seiko; et al.
Nuclear Instruments and Methods in Physics Research A, 929, p.113 - 120, 2019/06
Times Cited Count：23 Percentile：87.09(Instruments & Instrumentation)A nano-diamond is an attractive neutron reflection material below cold neutron energy. The total neutron cross section of a nano-diamond was derived from a neutron transmission measurement over the neutron energy range of 0.2 meV to 100 meV because total neutron cross section data were not available. The total cross section of a nano-diamond with particle size of approximately 5 nm increased with a decrease in neutron energy to 0.2 meV. It was approximately two orders of magnitude larger than that of graphite at 0.2 meV. The contribution of inelastic scattering to the total cross section was to be shown negligible small at neutron energies of 1.2, 1.5, 1.9, 2.6, and 5.9 meV in the inelastic neutron scattering measurement. Moreover, small-angle neutron scattering measurements of the nano-diamond showed a large scattering cross section in the forward direction for low neutron energies.
Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya*; Kofu, Maiko; Kawakita, Yukinobu; Inamura, Yasuhiro; Kambara, Wataru*; Aoyama, Kazuhiro*; Wakai, Daisuke*; Harada, Masahide; et al.
Journal of Physics; Conference Series, 1021(1), p.012031_1 - 012031_5, 2018/06
Times Cited Count：6 Percentile：93.12(Nuclear Science & Technology)Hirose, Takanori; Sakasegawa, Hideo; Nakajima, Motoki; Tanigawa, Hiroyasu
Fusion Engineering and Design, 98-99, p.1982 - 1985, 2015/10
Times Cited Count：5 Percentile：34.28(Nuclear Science & Technology)As a R&D activity on materials engineering for DEMO blanket in ITER-BA activity, characterization of F82H weld joints prepared with Tungsten-Inert-Gas (TIG) and electron beam (EB) have been investigated. In this work, 50 mm thick plates of F82H were welded using both processes. A similar-metal was employed as a filler for TIG welding. Post-weld-heat-treatment was conducted according to the conditions for Grade 91 defined as ASME P-No.15E, Group No.1. Although the maximum and the minimum hardness of the both joint are similar, the hardness distribution is quite different. The width of EB welds were smaller than that of TIG, and the hardness of EB weld metal was 10% higher than that of TIG. In the TIG welds, the strongest part was heat affected zone (HAZ) heated above phase transformation temperature, Ac1 and the hardness was very similar to the weld metal of EB joint, 280Hv. The hardness of TIG weld metal was around 260 Hv. Both welds demonstrated the smallest hardness, 180 Hv in the HAZ heated below Ac1 temperature. As a investigation of manufacturing process of box fabrication, second EB weld bead was perpendicularly put on the first EB bead. As a result, the second weld did not weaken the HAZ, but reduced the hardness of the weld metal to 260 Hv.
Nakajima, Motoki; Hirose, Takanori; Tanigawa, Hisashi; Enoeda, Mikio
Journal of Plasma and Fusion Research SERIES, Vol.11, p.69 - 72, 2015/03
Water-cooled blanket is an attractive concept for its compactness and its compatibility with the conventional technologies for PWR. For blanket application, the structural material is required to be as thin as possible for tritium breeding. On the other hand, it is also required the pressure tightness to withstand 15 MPa of internal pressure. Therefore it is necessary to understand the corrosion mechanism in high temperature pressurized water. The effects of water flow and DO in the test water on corrosion properties were investigated using rotating disk specimen in autoclave. In summary, the weight loss by flowing was occurred except for test with DO 8 ppm, and it was more pronounced at lower DO concentration. Since Fe
O
was observed on the specimen of small weight change, and the iron-poor layer thickness increased with decreasing the specimen weight, it seemed that the formation of FeO was effective for the suppression of weight loss.
Kanai, Akihiko*; Kasada, Ryuta*; Nakajima, Motoki; Hirose, Takanori; Tanigawa, Hisashi; Enoeda, Mikio; Konishi, Satoshi*
Journal of Nuclear Materials, 455(1-3), p.431 - 435, 2014/12
Times Cited Count：2 Percentile：14.00(Materials Science, Multidisciplinary)Enoeda, Mikio; Tanigawa, Hisashi; Hirose, Takanori; Nakajima, Motoki; Sato, Satoshi; Ochiai, Kentaro; Konno, Chikara; Kawamura, Yoshinori; Hayashi, Takumi; Yamanishi, Toshihiko; et al.
Fusion Engineering and Design, 89(7-8), p.1131 - 1136, 2014/10
Times Cited Count：22 Percentile：80.73(Nuclear Science & Technology)The development of a Water Cooled Ceramic Breeder (WCCB) Test Blanket Module (TBM) is being performed as one of the most important steps toward DEMO blanket in Japan. Regarding the fabrication technology development using F82H, the fabrication of a real scale mockup of the back wall of TBM was completed. Also the assembling of the complete box structure of the TBM mockup and planning of the pressurization testing was studied. The development of advanced breeder and multiplier pebbles for higher chemical stability was performed for future DEMO blanket application. From the view point of TBM test result evaluation and DEMO blanket performance design, the development of the blanket tritium simulation technology, investigation of the TBM neutronics measurement technology and the evaluation of tritium production and recovery test using D-T neutron in the Fusion Neutronics Source (FNS) facility has been performed.
Nakata, Toshiya; Komazaki, Shinichi*; Nakajima, Motoki*; Kono, Yutaka*; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Koyama, Akira*
Nihon Kinzoku Gakkai-Shi, 70(8), p.642 - 645, 2006/08
Times Cited Count：4 Percentile：32.73(Metallurgy & Metallurgical Engineering)no abstracts in English
Sb
Kogi, Masafumi*; Iwasa, Kazuaki*; Nakajima, Motoki*; Metoki, Naoto; Araki, Shingo; Bernhoeft, N.*; Mignot, J.-M.*; Gukasov, A.*; Sato, Hideyuki*; Aoki, Yuji*; et al.
Journal of the Physical Society of Japan, 72(5), p.1002 - 1005, 2003/05
Times Cited Count：199 Percentile：96.96(Physics, Multidisciplinary)no abstracts in English
Nakajima, Motoki; Kanai, Akihiko*; Hirose, Takanori; Tanigawa, Hisashi; Enoeda, Mikio
no journal, ,
no abstracts in English
Nakajima, Motoki
no journal, ,
Reduced activation ferritic/martensitic steel, F82H is the most promising candidate structural material for fusion blanket. Water-cooled ceramic breeder blanket is an attractive concept for its compactness and its compatibility with the technologies in conventional pressurized water reactor (PWR). For blanket application, the structural material is required to be as thin as possible for tritium breeding. On the other hand, it is also required the pressure tightness which could withstand internal pressure of 15 MPa. Therefore it is necessary to determine corrosion allowance for cooling tubes precisely. This work reports corrosion properties of F82H in high temperature pressurized water. Moreover, the effects of water flow on corrosion properties were investigated using rotating disk specimen in autoclave.
Harada, Masahide; Abe, Yutaka*; Oikawa, Kenichi; Kawasaki, Takuro; Kawamura, Seiko; Nakajima, Kenji; Inamura, Yasuhiro; Takahashi, Ryuta*; Teshigawara, Makoto; Oi, Motoki; et al.
no journal, ,
no abstracts in English
Tanigawa, Hiroyasu*; Nakajima, Motoki*; Sakasegawa, Hideo; Ando, Masami*; Watanabe, Yoshiyuki*; Nozawa, Takashi*; Kato, Yutai*; Nakata, Toshiya*
no journal, ,
Nakajima, Motoki; Hirose, Takanori; Gwon, H.; Tanigawa, Hisashi; Kawamura, Yoshinori
no journal, ,
As the primary candidate of ITER-TBM of Japan, development of WCCB TBM is being performed. In this blanket, the high temperature pressurized water was used as the coolant. Therefore it is necessary to understand the corrosion mechanism in high temperature pressurized water. Additionally, it is also required that understanding of corrosion properties of temperature ranging from 543K to 593K, because inlet and outlet temperatures of TBM are 543K and 593K, respectively. In this study, the corrosion test was performed at temperature ranging from 543K to 593K in deaerated (20ppb DO) and oxygen-saturated (8ppm DO) high temperature water.
Tanigawa, Hisashi; Gwon, H.; Hirose, Takanori; Nakajima, Motoki; Kawamura, Yoshinori
no journal, ,
Blanket in fusion nuclear reactor has three functions such as neutron shielding, heat recovery and tritium breeding. Blankets with ceramic breeder materials has a box structure made of reduced activation ferritic/martensitic steel, and pebbles of breeder and neutron multiplier materials are packed into the box. Heat and neutron loads on the blanket are cooled by high temperature and pressure coolant such as water and helium. In this study, strength and pressure integrity are assessed for the water-cooled ceramic breeder blanket developed in JAEA. Existing design standards for pressure equipment are used in the analysis and their applicability to the fusion blanket is discussed.
Hirose, Takanori; Tanigawa, Hisashi; Nakajima, Motoki; Gwon, H.; Miyata, Satoru; Sato, Satoshi; Kawamura, Yoshinori; Yamanishi, Toshihiko
no journal, ,
no abstracts in English
Gwon, H.; Tanigawa, Hisashi; Nakajima, Motoki; Hirose, Takanori; Kawamura, Yoshinori
no journal, ,
It is expected that the neutron wall loading in DEMO is larger than that in ITER, over 0.78 MW/m
. It is concerned that the decay heat due to the large neutron wall loading will lead to excessive temperature rising in blanket. In present study, the thermal response characteristics of blanket caused by the decay heat under LOCA were evaluated. In addition we considered how to effectively mitigate the excessive temperature rising based on the evaluation results.
Harada, Masahide; Abe, Yutaka*; Teshigawara, Makoto; Oi, Motoki; Ikeda, Yujiro; Oikawa, Kenichi; Nakajima, Kenji; Kawamura, Seiko
no journal, ,
By using neutron instruments, NOBORU and AMATERAS, in J-PARC spallation neutron source, we started to measure temperature dependent total and scattering cross section data of hydrogenous material ranging in thermal and cold neutron region. The cross section data of light water and ethanol were measured.
Gwon, H.; Tanigawa, Hisashi; Nakajima, Motoki; Hirose, Takanori; Kawamura, Yoshinori
no journal, ,
It is concerned that the temperature of the blanket would increase excessively due to the decay heat even after the plasma shutdown. In present study, we focuses the relationship between the blanket structures and the passive cooling performance and considers how to effectively mitigate the excessive temperature rising due to the decay heat. The arrangement of both pebble beds and the ribs was changed as a way to relieve the temperature rising. The thermal response characteristics of the modified blanket models were evaluated by using a two-dimensional nuclear-thermal-coupled analysis code, DOHEAT3. The TBR of each model was also evaluated. Based on the results, the useful design policies for blanket were proposed from the viewpoint of the decay heat removal.
Nakajima, Motoki; Hirose, Takanori; Tanigawa, Hisashi; Enoeda, Mikio
no journal, ,
no abstracts in English
