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Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Journal Articles

Influence of microstructure on IASCC growth behavior of neutron irradiated type 304 austenitic stainless steels in simulated BWR condition

Kaji, Yoshiyuki; Miwa, Yukio*; Shibata, Akira; Nakano, Junichi; Tsukada, Takashi; Takakura, Kenichi*; Nakata, Kiyotomo*

International Journal of Nuclear Energy Science and Engineering, 2(3), p.65 - 71, 2012/09

Crack growth rate (CGR) tests have been conducted with neutron irradiated compact tension (CT) specimens. The specimens were irradiated in the core region of the Japan Materials Testing Reactor (JMTR) in simulated BWR water environments at 288 $$^{circ}$$C from 0.37 to 5.55$$times$$10$$^{25}$$ n/m$$^{2}$$ (E$$>$$ 1 MeV) (0.62 to 9.2 dpa). The CGRs of base metals in high electrochemical corrosion potential (ECP) condition with 10 $$<$$ stress intensity factor, K $$<$$ 30 MPam$$^{1/2}$$, increased with increasing neutron fluence until 2 dpa and the CGRs were almost the same from 2 to 10 dpa. We investigated the influence of microstructure on CGR by microstructure observation and local strain measurement around the precipitate. This paper will discuss the relationship between CGR and microstructure, radiation hardening, radiation induced segregation.

Journal Articles

Influence of microstructure on IASCC growth behavior of neutron irradiated type 304 austenitic stainless steels in simulated BWR condition

Kaji, Yoshiyuki; Miwa, Yukio; Shibata, Akira; Nakano, Junichi; Tsukada, Takashi; Takakura, Kenichi*; Nakata, Kiyotomo*

Proceedings of 14th International Conference on Environmental degradation of Materials in Nuclear Power Systems (CD-ROM), p.1181 - 1191, 2009/08

The CGR tests of neutron irradiated Type 304 SS were conducted in BWR conditions and the results were compared with those of Type 304L and 316L SS, and following results were obtained. (1) The CGR increase with increasing neutron fluence and the power law of K on the CGR was observed above F2 neutron fluence level (1.4 dpa). The different tendency is observed between Type 304 SS and L-grade SS (Type 304L and 316L SS) with increasing neutron fluence above F3 (4.3 dpa) level. (2) The CGR of Type 304 SS is slightly small as compared with those of Type 304L and 316L SS at the same neutron fluence and shows an increasing tendency above 4 dpa and reaches to 1.0$$times$$10$$^{-9}$$m/s in 9 dpa. (3) The neutron fluence dependence on uniform elongation is different with Type 304, 304L SS and Type 316L SS, that is, the neutron fluence in which the local deformation like channeling deformation is dominant, is high for Type 316L SS.

Journal Articles

Evaluation of deformation behavior of In grains and grain boundaries of L-grade austenitic stainless steel 316L

Nagashima, Nobuo*; Hayakawa, Masao*; Tsukada, Takashi; Kaji, Yoshiyuki; Miwa, Yukio*; Ando, Masami*; Nakata, Kiyotomo*

Atsuryoku Gijutsu, 47(4), p.236 - 244, 2009/07

In this study, micro-hardness tests and AFM observations were performed on SUS316L low-carbon austenitic stainless steel pre-strained by cold rolling to investigate its deformation behavior. The following results were obtained. Despite the fact that the same plastic strain was applied, post-tensile test AFM showed narrower slip-band spacing in a reduction in area of 30% cold-rolled specimen than the unrolled specimen. Concentrated slip bands were observed near grain boundaries. Micro-hardness exceeding 300 was found to occur frequently in after tensile test specimens with a reduction in area of 30% or more, particularly at grain boundaries. It is suggested that the nonuniformity of deformation at grain boundaries plays an important role of IGSCC crack propagation mechanism of low-carbon austenitic stainless steel.

Journal Articles

Recent results on beryllium and beryllides in Japan

Mishima, Yoshinao*; Yoshida, Naoaki*; Kawamura, Hiroshi; Ishida, Kiyohito*; Hatano, Yuji*; Shibayama, Tamaki*; Munakata, Kenzo*; Sato, Yoshiyuki*; Uchida, Munenori*; Tsuchiya, Kunihiko; et al.

Journal of Nuclear Materials, 367-370(2), p.1382 - 1386, 2007/08

 Times Cited Count:25 Percentile:84.96(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years

Kawamura, Kenji*; Parrenin, F.*; Lisiecki, L.*; Uemura, Ryu*; Vimeux, F.*; Severinghaus, J. P.*; Hutterli, M. A.*; Nakazawa, Takakiyo*; Aoki, Shuji*; Jouzel, J.*; et al.

Nature, 448(7156), p.912 - 916, 2007/08

 Times Cited Count:309 Percentile:96.49(Multidisciplinary Sciences)

We present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations.

Journal Articles

Development of beryllides as advanced neutron multipliers for fusion blankets

Tsuchiya, Kunihiko; Kawamura, Hiroshi; Mishima, Yoshinao*; Yoshida, Naoaki*; Tanaka, Satoru*; Uchida, Munenori*; Ishida, Kiyohito*; Shibayama, Tamaki*; Munakata, Kenzo*; Sato, Yoshiyuki*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 83(3), p.207 - 214, 2007/03

no abstracts in English

Journal Articles

IASCC crack growth rate of neutron irradiated low carbon austenitic stainless steels in simulated BWR condition

Chatani, Kazuhiro*; Takakura, Kenichi*; Ando, Masami*; Nakata, Kiyotomo*; Tanaka, Shigeaki*; Ishiyama, Yoshihide*; Hishida, Mamoru*; Kaji, Yoshiyuki

Proceedings of 13th International Conference on Environmental Degradation of Materials in Nuclear Power Systems (CD-ROM), 9 Pages, 2007/00

Crack growth rate (CGR) tests have been conducted with neutron irradiated compact tension (CT) specimens. The CGR tests of 316L and 304L base metals irradiated from 0.516 to 1.07$$times$$10$$^{25}$$n/m$$^{2}$$ (E$$>$$1MeV), and of 316L and 308L weld metals irradiated from 0.523 to 0.541$$times$$10$$^{25}$$n/m$$^{2}$$ (E$$>$$1MeV) were performed using the reversing dc potential drop (DCPD) method under constant load at a few average stress intensity factors (K) and electrochemical corrosion potential (ECP) conditions at 288$$^{circ}$$C in water. CGRs of base metals were increased with increasing neutron fluence. Clear reductions in CGRs of base metals and weld metals were measured with decreasing ECP levels.

Journal Articles

CGR behavior of low carbon stainless steel of hardened heat affected zone in PLR piping weld joints

Ando, Masami*; Nakata, Kiyotomo*; Ito, Mikiro*; Tanaka, Norihiko*; Koshiishi, Masato*; Obata, Ryoji*; Miwa, Yukio; Kaji, Yoshiyuki; Hayakawa, Masao*

Proceedings of 13th International Conference on Environmental Degradation of Materials in Nuclear Power Systems (CD-ROM), 16 Pages, 2007/00

Long term SCC growth tests for nuclear grade stainless steel (SUS316(NG)) were conducted in a simulated BWR environment using specimens taken from mock-up PLR piping weld joints to obtain the crack growth rate (CGR) of the hardened heat affected zone due to weld shrinkage around weld, in order to develop the CGR curve which will be used for flaw evaluation. The piping joints were made of forged and extracted materials with several welding techniques. The obtained CGRs were higher than that of solution heat treated material. The CGRs for hardened SUS316(NG) have a correlation with hardness regardless of materials and welding techniques. The CGRs increased with hardness in the range from 210 to 250 Hv. The CGR acceleration mechanism in hardened HAZ of low carbon stainless steel was estimated based on the strain distribution and the AFM image around a SCC crack tip. It was suggested that the interaction of the plastic strain gradient at a crack tip and local strain along GBs.

Journal Articles

Deformation behavior around grain boundaries for SCC propagation in hardened low-carbon austenitic stainless steel by micro hardness test

Nagashima, Nobuo*; Hayakawa, Masao*; Tsukada, Takashi; Kaji, Yoshiyuki; Miwa, Yukio; Ando, Masami*; Nakata, Kiyotomo*

Proceedings of 13th International Conference on Environmental Degradation of Materials in Nuclear Power Systems (CD-ROM), 15 Pages, 2007/00

Stress corrosion cracking (SCC) was found in shroud and PLR piping made of low-carbon austenitic stainless steels in Japanese BWR plants. The intergranular type (IG) SCC propagated in hardened heat affected zones (HAZ) around welds. Strength behavior and local plastic deformation for a low-carbon austenitic stainless steel 316L, cold-rolled at the reductions in area of 10, 30% at room temperature to simulate the hardened HAZ, were measured by a micro-hardness test machine and observed by atomic force microscopy (AFM), respectively. The tensile deformation at yield point (0.2% plastic strain) had given to the work-hardened 316L to simulate the plastic zone at the crack tip. It is suggested that one of the IGSCC propagation mechanisms for 316L was related with the intergranular strength behavior and local plastic deformation around grain boundaries.

Journal Articles

Status of beryllium R&D in Japan

Kawamura, Hiroshi; Tsuchiya, Kunihiko; Mishima, Yoshinao*; Yoshida, Naoaki*; Munakata, Kenzo*; Ishida, Kiyohito*; Hatano, Yuji*; Shibayama, Tamaki*; Sato, Yoshiyuki*; Uchida, Munenori*; et al.

INL/EXT-06-01222, p.1 - 7, 2006/02

no abstracts in English

Journal Articles

Present status of beryllide R&D as neutron multiplier

Kawamura, Hiroshi; Takahashi, Heishichiro*; Yoshida, Naoaki*; Mishima, Yoshinao*; Ishida, Kiyohito*; Iwadachi, Takaharu*; Cardella, A.*; Van der Laan, J. G.*; Uchida, Munenori*; Munakata, Kenzo*; et al.

Journal of Nuclear Materials, 329-333(1), p.112 - 118, 2004/08

 Times Cited Count:31 Percentile:87.68(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

EXAFS study on local structural changes in amorphous Fe-Zr-B alloys

Nakata, Yoshiyuki*; Hara, Naoyuki*; Hirotsu, Yoshihiko*; Emura, Shuichi*; Makino, Akihiro*; Uruga, Tomoya*; Harada, Makoto*; Nishihata, Yasuo; Yoneda, Yasuhiro; Kubozono, Yoshihiro*

Japanese Journal of Applied Physics, 38(Suppl.38-1), p.404 - 407, 1999/06

The EXAFS spectra on Zr K-edge are investigated for as-formed Fe-7at%Zr-3at%B amorphous alloys and annealed ones at 693 K and 773 K for an hour in order to reveal local structural changes due to annealing. The analysis shows that the atomic distances of Fe-Zr and Zr-Zr pairs increase during annealing and approach those in a Fe3Zr or/and Fe2Zr metallic comound. The change in the atomic distances suggests that medium range ordered clusters should be formed during annealing.

Journal Articles

The XAFS beamline BL01B1 at SPring-8

Uruga, Tomoya*; Tanida, Hajime*; Yoneda, Yasuhiro; Takeshita, Kunikazu*; Emura, Shuichi*; Takahashi, Masao*; Harada, Makoto*; Nishihata, Yasuo; Kubozono, Yoshihiro*; Tanaka, Tsunehiro*; et al.

Journal of Synchrotron Radiation, 6(Part3), p.143 - 145, 1999/05

An x-ray absorption fine-structure (XAFS) spectroscopy beamline, BL01B1, was installed at a bending magnet source at SPring-8 and has been open to users since October 1997. It was designed for XAFS experiments covering a wide energy range. Position tables and automatical control programs were established to adjust the x-ray optics and achieve the designed performance of the beamline under each experimental condition. This has enabled conventional XAFS measurements to be made with a good data quality from 4.5 to 110 keV.

Oral presentation

Analysis of deformation behavior at SCC crack tip, 3; Plastic deformation analysis by EBSP method

Kaji, Yoshiyuki; Miwa, Yukio; Tsukada, Takashi; Nagashima, Nobuo*; Hayakawa, Masao*; Ando, Masami*; Nakata, Kiyotomo*; Koshiishi, Masato*

no journal, , 

In recent years, incidents of the stress corrosion cracking (SCC) were frequently reported that occurred in the weld part of core shroud and primary loop recirculation (PLR) piping of low carbon stainless steels, and the cause investigation and measure become the present important issue. In this study, to investigate the effect of plastic deformation behavior at the crack, analyses of plastic deformation behavior at the SCC crack tip were performed by electron back-scattering diffraction pattern (EBSP) method. SCC crack propagated along the grain boundary in the 45 degree direction of a fatigue crack, especially random grain boundary. The plastic deformation showed 10 to 20% in the one grain region of the crack. The plastic deformation behavior was different in both of a SCC crack and large plastic deformation was observed on one side of grain. From these results, it was considered that SCC crack propagation behavior was controlled by plastic deformation of very near crack tip.

Oral presentation

Investigation of effect of dose rate on SCC growth behavior of irradiated materials

Kaji, Yoshiyuki; Miwa, Yukio; Ugachi, Hirokazu; Tsukada, Takashi; Shibata, Akira; Kato, Yoshiaki; Arai, Kensaku*; Nakata, Kiyotomo*

no journal, , 

In order to investigate the effect of dose rate on SCC growth behavior, the SCC growth tests were carried out under simulated boiling water reactor (BWR) water conditions using irradiated materials at different dose rate. It was confirmed that the effect of dose rate on SCC growth rate was considered to be small.

Oral presentation

IASCC growth behavior evaluation of neutron-irradiated SUS304 stainless steel under BWR simulated high temperature water condition

Kaji, Yoshiyuki; Miwa, Yukio; Shibata, Akira; Kato, Yoshiaki; Taguchi, Taketoshi; Nakano, Junichi; Tsukada, Takashi; Takakura, Kenichi*; Nakata, Kiyotomo*

no journal, , 

SCC growth tests have been carried out using type 304 stainless steel that had been pre-irradiated 0.62 to 9.2dpa under BWR simulated high temperature water condition at 288$$^{circ}$$C in the JMTR. This paper describes the investigated results of crack growth rate characteristics from the point of view of microstructure, radiation hardening and radiation induced segregation.

Oral presentation

SCC growth behavior of type 304 stainless steel irradiated under the different dose rates at JMTR

Tsukada, Takashi; Kaji, Yoshiyuki; Ugachi, Hirokazu; Nakano, Junichi; Kondo, Keietsu; Arai, Kensaku*; Nakata, Kiyotomo*

no journal, , 

In order to investigate the effect of neutron dose rate on the mechanical property and stress corrosion cracking (SCC) growth behavior of type 304 stainless steel, the crack growth rate (CGR) test, tensile test and microstructure observation have been conducted after neutron irradiation. The specimens were irradiated up to about 1dpa with different dose rates in the Japan Materials Testing Reactor (JMTR). The radiation hardening increased with the high dose rate condition, and a little difference of radiation-induced segregation at grain boundaries was observed in specimens irradiated by different dose rates. There was no remarkable effect of dose rates on IASCC growth behavior.

Oral presentation

Cs$$_{2}$$O and ZrO$$_{2}$$ containing Cr$$_{2}$$O$$_{3}$$-CoO-Al$$_{2}$$O$$_{3}$$-Fe$$_{2}$$O$$_{3}$$-P$$_{2}$$O$$_{5}$$ glasses

Yano, Tetsuji*; Kishi, Tetsuo*; Nakata, Yoshiyuki*; Kofuji, Hirohide; Takeuchi, Masayuki

no journal, , 

Oral presentation

Secure and development of radiation protection experts to be active in nuclear emergency

Takada, Chie; Nakano, Masanao; Munakata, Masahiro; Yoshida, Tadayoshi; Yokosuka, Yoshiyuki; Yamada, Junya; Maeda, Eita; Watanabe, Yuki; Tomioka, Akifumi; Momose, Takumaro

no journal, , 

no abstracts in English

Oral presentation

Current and future perspectives of collaborative activities of academic society on radiation protection, 3; Efforts to train and secure on radiation protection experts in nuclear emergencies

Takada, Chie; Nakano, Masanao; Munakata, Masahiro; Yoshida, Tadayoshi; Yokosuka, Yoshiyuki; Yamada, Junya; Maeda, Eita; Watanabe, Yuki; Tomioka, Akifumi; Momose, Takumaro

no journal, , 

no abstracts in English

21 (Records 1-20 displayed on this page)