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Journal Articles

Development of in-vessel components of the microfission chamber for ITER

Ishikawa, Masao; Kondoh, Takashi; Okawa, Kiyofumi*; Fujita, Kyoichi*; Yamauchi, Michinori*; Hayakawa, Atsuro*; Nishitani, Takeo; Kusama, Yoshinori

Review of Scientific Instruments, 81(10), p.10D308_1 - 10D308_3, 2010/10

 Times Cited Count:2 Percentile:14.37(Instruments & Instrumentation)

Microfission chambers (MFCs) will provide total neutron source strength in ITER. The MFC is a pencil-sized gas counter containing the fissile material, $$^{235}$$U. The MFCs will be installed behind blanket modules in the vacuum vessel (VV). Double coaxial mineral insulated (MI) cables will carry signals from the MFCs to the upper port. Though the MI cables will be installed at a factory of the vacuum vessel or ITER assembly hall, detectors with $$^{235}$$U will be installed to the vacuum vessel at the tokamak pit. Then, the MI cable should be connected in the vacuum vessel. In this work, the connection of the MI cable with the MFC was conceptually designed. The MI cable should be also installed with small curvature radius (R) of 100 $$sim$$ 200 mm to avoid the VV structure and other diagnostics. So, the vending test of the MI cable was conducted. As a result, damages leak, electrical disconnection and the change in insulation resistance have not been observed at R = 100 mm.

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.

JAEA Reports

Multi-scale analysis of deformation behavior at SCC crack tip, 3 (Contract research)

Kaji, Yoshiyuki; Miwa, Yukio; Tsukada, Takashi; Hayakawa, Masao*; Nagashima, Nobuo*

JAEA-Research 2008-064, 118 Pages, 2008/08

JAEA-Research-2008-064.pdf:26.9MB

This report describes a result of the research conducted by the Japan Atomic Energy Agency and the National Institute for Materials Science under contract with JNES that was concerned with a multi-scale analysis of plastic deformation behavior at the crack tip of SCC. In this research, analyses of the plastic deformation behavior and microstructure around the crack tip were performed in a nano-order scale. The hardness measured in nano, meso and macro scales was employed as a common index of the strength, and the essential data necessary to understand the SCC propagation behavior were acquired and analyzed that are mainly a size of plastic deformation region and a microstructural information in the region, e.g. data of crystallografy, microscopic deformation and dislocations at the inside of grains and grain boundaries.

JAEA Reports

Detail design of microfission chamber for fusion power diagnostic on ITER

Ishikawa, Masao; Kondoh, Takashi; Hayakawa, Atsuro*; Nishitani, Takeo; Kusama, Yoshinori

JAEA-Technology 2007-062, 57 Pages, 2007/12

JAEA-Technology-2007-062.pdf:45.95MB

The microfission chambers (MFC)provide time-resolved measurements of the global neutron source strength and fusion power from ITER. In the previous work, it was found that combination of the MFC for low power operation and for high power operation can cover the target measurement requirement of ITER. Signals from the MFC are transferred by double coaxial mineral cable (MI) cable. These MFC will be installed in the vacuum vessel, so that the MI cables should be placed in the vacuum vessel. In this design work, the placing route of the MI cables from the installation position of the microfission chamber to the feed-through in the upper port is designed. As far placing of the MI cable, since the MI cable is filled with Ar gas at 14.6 atom, the double pipe structure that the outer pipe covers the MI cable is adopted in order to prevent the gas leak into the vacuum vessel. The exhaust system of the double pipe is also designed for detection and exhaust of the leaked Ar gas.

JAEA Reports

Multi-scale analysis of deformation behavior at SCC crack tip, 2 (Contract research)

Kaji, Yoshiyuki; Miwa, Yukio; Tsukada, Takashi; Hayakawa, Masao*; Nagashima, Nobuo*

JAEA-Research 2007-008, 69 Pages, 2007/03

JAEA-Research-2007-008.pdf:25.87MB

The research was carried out to evaluate the validity of the SCC growth data acquired in the IGSCC project based on a mechanistic understanding of SCC. The hardness measured in nano, meso and macro scales was employed as a common index of the strength, and the essential data necessary to understand the SCC propagation behavior were acquired and analyzed that are mainly a size of plastic deformation region and a microstructural information in the region, e.g. data of crystallografy, microscopic deformation and dislocations at the inside of grains and grain boundaries. In this year, we analyzed the state of plastic deformation region at the crack tip of IGSCC under various conditions and investigated relationship between crack growth behavior and stress intensity factor. Especially, we investigated in detail about two different hardened specimens used in the SCC growth tests in the IGSCC project.

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.

JAEA Reports

Multi-scale analysis of deformation behavior at SCC crack tip (Contract research)

Kaji, Yoshiyuki; Miwa, Yukio; Tsukada, Takashi; Hayakawa, Masao*; Nagashima, Nobuo*; Matsuoka, Saburo*

JAERI-Research 2005-029, 156 Pages, 2005/09

JAERI-Research-2005-029.pdf:57.24MB

This report describes a result of the research conducted under contract with JNES that was concerned with a multi-scale analysis of plastic deformation behavior at the crack tip of SCC. The research was carried out to evaluate the validity of the SCC growth data acquired in the IGSCC project based on a mechanistic understanding of SCC. For the purpose, in this research, analyses of the plastic deformation behavior and microstructure around the crack tip were performed in a nano-order scale. The hardness measured in nano, meso and macro scales was employed as a common index of the strength, and the essential data necessary to understand the SCC propagation behavior were acquired and analyzed that are mainly a size of plastic deformation region and a microstructural information in the region, e.g. data of crystallografy, microscopic deformation and dislocations at the inside of grains and grain boundaries.

Journal Articles

Isomer-scope: A new instrument for in-beam $$gamma$$-ray spectroscopy through deep inelastic collisions

Ishii, Tetsuro; *; ; Makishima, Akiyasu*; Hossain, I.*; Hayakawa, Takehito*; Kono, Toshiyuki*; Ogawa, Masao*

Nuclear Instruments and Methods in Physics Research A, 395(2), p.210 - 216, 1997/00

 Times Cited Count:39 Percentile:92.7(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

2nd power-up test for JRR-2

Kambara, Toyozo; Uno, Hidero; Shoda, Katsuhiko; Hirata, Yutaka; Shoji, Tsutomu; Kohayakawa, Toru; Takayanagi, Hiroshi; Fujimura, Tsutomu; Morita, Morito; Ichihara, Masahiro; et al.

JAERI 1045, 11 Pages, 1963/03

JAERI-1045.pdf:0.72MB

no abstracts in English

JAEA Reports

The First loading fuel elements and power-up for JRR-2

JRR-2 Control Office; Kambara, Toyozo; Shoda, Katsuhiko; Hirata, Yutaka; Shoji, Tsutomu; Kohayakawa, Toru; Morozumi, Minoru; Kambayashi, Yuichiro; Shitomi, Hajimu; Kokanezawa, Takashi; et al.

JAERI 1027, 57 Pages, 1962/09

JAERI-1027.pdf:4.76MB

no abstracts in English

JAEA Reports

Critical experiments and characteristic measurement for JRR-2

JRR-2 Critical Experiments Group; Kambara, Toyozo; Shoda, Katsuhiko; Hirata, Yutaka; Shoji, Tsutomu; Kohayakawa, Toru; Morozumi, Minoru; Kambayashi, Yuichiro; Shitomi, Hajimu; Kokanezawa, Takashi; et al.

JAERI 1025, 62 Pages, 1962/03

JAERI-1025.pdf:4.6MB

no abstracts in English

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.

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