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Nemoto, Yoshiyuki; Oishi, Makoto; Ito, Masayasu; Kaji, Yoshiyuki; Keyakida, Satoshi*
Hozengaku, 14(4), p.83 - 90, 2016/01
Authors previously reported that magnetic data obtained by using Eddy current method and AC magnetization method showed correlation with the increase of susceptibility of the irradiation assisted stress corrosion cracking (IASCC) on neutron irradiated austenitic stainless alloy specimens. To discuss the mechanism of the correlation, microstructure observation was conducted on the irradiated specimen, and magnetic permalloy phase (FeNi
) formation along grain boundary was revealed in this work. From this result, the radiation induced magnetic phase formation along grain boundary seems to be a factor of the magnetic property change of the irradiated materials, and related to the correlation between magnetic data and IASCC susceptibility. In addition, sensor probe development was conducted in this work to obtain higher sensitivity and resolution. It was applied for magnetic measurement on type304 stainless steel irradiated up to different doses. In this case, magnetic ferrite phase was existed in the type304 stainless steel sample before irradiation therefore it was concerned that magnetic measurement on the irradiated ones would be disturbed by the magnetic signal from the pre-existing ferrite phase. In the magnetic measurements, increase of the magnetic data was clearly seen on the irradiated specimens. Thus, it was thought that the developed magnetic measurement technics can be applied for the irradiated austenite stainless steels which contain certain quantity of ferrite phase before irradiation.
Takaya, Shigeru; Arakawa, Hisashi*; Keyakida, Satoshi*
Hozengaku, 14(3), p.81 - 87, 2015/10
A magnetic sensor which can be applied to measurement at elevated temperature was newly developed. It is a kind of flux gate magnetic sensor. Permendur was employed for a magnetic core instead of Permalloy which is commonly used because Permendur has much higher Curie point, about 1000
C. Heat resistant ceramic coating Cu wires were used for coils. External magnetic field is detected by shift of peak position of differential permeability during induction of triangular excitation current. A magnetic core has race track shape with a fine part to make peak position more clear and increase detectability. The output of the developed sensor showed good linearity with external magnetic field even at 500C. Furthermore, the durability of the sensor was discussed, and it was shown that decrease in coil performance after some operation at elevated temperature seems to be a critical issue.
Nemoto, Yoshiyuki; Keyakida, Satoshi*; Uchimoto, Tetsuya*; Takaya, Shigeru; Tsukada, Takashi
International Journal of Applied Electromagnetics and Mechanics, 35(2), p.123 - 139, 2011/02
Times Cited Count：1 Percentile：11.16(Engineering, Electrical & Electronic)JP, 2008-301850
Patent publication (In Japanese)
This paper presents a study conducted to develop a diagnostic system that can detect IASCC precursors in stainless steels by measuring the magnetic properties of the material. The eddy current method and alternating current (AC) magnetization method were used, as these will be more practical for use in actual reactors. Probes were developed for these measurement methods, providing sufficient tolerance for environments in nuclear reactors. An attempt was also made to improve spatial resolution by manufacturing a smaller probe. A sensor system was designed for remote control, performance tests were conducted by measuring neutron-irradiated specimens and mock specimens, and magnetic data were evaluated by comparing the IASCC susceptibility of the specimens. It was proved that the sensor system developed in this study is capable of detecting IASCC precursors. Further developments necessary for application in actual nuclear reactors and the mechanism of correlation between magnetic properties and IASCC susceptibility were also discussed.
Oikawa, Ryota*; Uchimoto, Tetsuya*; Takagi, Toshiyuki*; Urayama, Ryoichi*; Nemoto, Yoshiyuki; Takaya, Shigeru; Keyakida, Satoshi*
International Journal of Applied Electromagnetics and Mechanics, 33(3-4), p.1303 - 1308, 2010/10
Times Cited Count：5 Percentile：35(Engineering, Electrical & Electronic)This paper discusses feasibility of non-linear eddy current method to evaluate material degradations of austenitic stainless steels associated with irradiation assisted stress corrosion cracking (IASCC). For the purpose, tensile test at elevated temperature was conducted using model alloys simulating radiation induced segregation (RIS), then magnetization curve of the specimens was measured by vibrating sample magnetometer (VSM), and microstructure of magnetization was observed by magnetic force microscopy (MFM). Moreover non-linear eddy current method was carried out. It was shown that the 3rd higher harmonic ration of the pick-up signal would relate to nominal strain of the specimens.
Takaya, Shigeru; Nemoto, Yoshiyuki; Uchimoto, Tetsuya*; Keyakida, Satoshi*
Nihon AEM Gakkai-Shi, 17(1), p.156 - 161, 2009/03
In a previous study, authors showed experimentally the correlation between leakage magnetic flux density and irradiation assisted stress corrosion cracking susceptibility of high purity model austenitic stainless steels. This study aimed to investigate mechanism of the correlation. Tensile test at elevated temperature and aging test were conducted on materials simulating irradiation-induced segregation, and leakage magnetic flux density was measured before and after these tests in order to study the influence of chemical composition change and lattice defect to leakage magnetic flux density. Furthermore, dependency of magnetic moment on chemical composition and vacancy was evaluated by first principle calculation. As result, it was shown that leakage magnetic flux density of irradiated materials is thought to increase in severe irradiation-induced segregation region with and without vacancy.
Nemoto, Yoshiyuki; Keyakida, Satoshi*; Uchimoto, Tetsuya*; Takaya, Shigeru; Tsukada, Takashi
Hozengaku, 7(4), p.57 - 68, 2009/01
Authors previously reported leakage magnetic flux density measured by flux gate (FG) sensor seems to depend on irradiation assisted stress corrosion cracking (IASCC) susceptibility of neutron irradiated austenitic stainless steels. This study aimed to evaluate possibility to develop diagnostic method to detect symptom of IASCC by more practical methods such as Eddy current method and AC magnetization method. Magnetic properties of neutron irradiated specimens and mockup specimens were studied and dependence on IASCC susceptibility was revealed. Microstructure observation using transmission electron microscope (TEM) was conducted to study magnetic phase formation by radiation induced segregation. It was shown that measurement of magnetic signal changed by magnetic phase formation along grain boundaries caused by radiation induced segregation would be a mechanism of the diagnostic method to detect symptom of IASCC.
Nemoto, Yoshiyuki; Uchimoto, Tetsuya*; Keyakida, Satoshi*; Nagae, Yuji; Takaya, Shigeru; Ebine, Noriya; Tsukada, Takashi
no journal, ,
It was suggested by the authors that electromagnetic method could detect irradiation assisted stress corrosion cracking (IASCC) of austenitic stainless steel in advance of crack initiation. Authors investigated the mechanism using mock specimens of radiation induced segregation (RIS). SCC susceptibility and electromagnetic properties of the mock specimens were studied. Results were compared with the data of irradiated specimens and mechanism of electromagnetic diagnosis were discussed. A sensor system will be developed by application of these mechanism.
Nemoto, Yoshiyuki; Takaya, Shigeru; Ebine, Noriya; Tsukada, Takashi; Uchimoto, Tetsuya*; Keyakida, Satoshi*
no journal, ,
no abstracts in English
Nemoto, Yoshiyuki; Miwa, Yukio; Takaya, Shigeru; Ebine, Noriya; Tsukada, Takashi; Uchimoto, Tetsuya*; Keyakida, Satoshi*
no journal, ,
Authors reported previously that magnetic parameter seems to depend on irradiation assisted stress corrosion cracking susceptibility of high purity model austenitic stainless steels. This study aimed to investigate mechanism of the dependence. Electron diffraction patterns obtained by transmission electron microscopy were evaluated to study precipitation in irradiated specimens. Influence of element segregation on electro magnetic property of austenitic stainless steel was investigated applying mockup specimens. It was shown that magnetic phases were formed in irradiated austenitic stainless steels. Mockup experiments showed that radiation induced segregation can bring magnetic phase formation along grain boundaries. The magnetic phase was thought to involve with mechanism of magnetic parameter dependence on irradiation assisted stress corrosion cracking susceptibility.
Nemoto, Yoshiyuki; Miwa, Yukio; Takaya, Shigeru; Ebine, Noriya; Tsukada, Takashi; Uchimoto, Tetsuya*; Keyakida, Satoshi*
no journal, ,
Authors reported previously that magnetic parameter seems to depend on irradiation assisted stress corrosion cracking susceptibility of high purity model austenitic stainless steels. This study aimed to investigate mechanism of the dependence. Electron diffraction patterns obtained by transmission electron microscopy were evaluated to study precipitation in irradiated specimens. Influence of element segregation on electro magnetic property of austenitic stainless steel was investigated applying mockup specimens. It was shown that magnetic phases were formed in irradiated austenitic stainless steels. Mockup experiments showed that radiation induced segregation can bring magnetic phase formation along grain boundaries. The magnetic phase was thought to involve with mechanism of magnetic parameter dependence on irradiation assisted stress corrosion cracking susceptibility.
Takaya, Shigeru; Nemoto, Yoshiyuki; Uchimoto, Tetsuya*; Keyakida, Satoshi*
no journal, ,
In a previous study, authors showed experimentally the correlation between leakage magnetic flux density and irradiation assisted stress corrosion cracking susceptibility of high purity model austenitic stainless steels. This study aimed to investigate mechanism of the correlation. Tensile test at elevated temperature and aging test were conducted on materials simulating irradiation-induced segregation, and leakage magnetic flux density was measured before and after these tests in order to study the influence of chemical composition change and lattice defect to leakage magnetic flux density. Furthermore, dependency of magnetic moment on lattice constant was evaluated by first principle calculation. As result, it was shown that leakage magnetic flux density of irradiated materials is thought to increase in severe irradiation-induced segregation region.
Uchimoto, Tetsuya*; Takagi, Toshiyuki*; Nemoto, Yoshiyuki; Takaya, Shigeru; Keyakida, Satoshi*
no journal, ,
This paper discusses feasibility of non-linear eddy current method to evaluate material degradations of austenitic stainless steels associated with irradiation assisted stress corrosion cracking. For the purpose, tensile test at elevated temperature was conducted on materials simulating radiation-induced segregation, and non linear harmonic analysis of eddy current was carried out for the tensile test specimens. In addition, microstructure of magnetization of the tensile test specimens was observed by magnetic force microscopy. It was shown that non linear harmonics of eddy current is associated with the Cr depletion and Ni enrichment at grain boundary and intragranular phase transformation.
Oikawa, Ryota*; Uchimoto, Tetsuya*; Takagi, Toshiyuki*; Urayama, Ryoichi*; Nemoto, Yoshiyuki; Takaya, Shigeru; Keyakida, Satoshi*
no journal, ,
no abstracts in English
Uchimoto, Tetsuya*; Oikawa, Ryota*; Takagi, Toshiyuki*; Urayama, Ryoichi*; Nemoto, Yoshiyuki; Takaya, Shigeru; Keyakida, Satoshi*
no journal, ,
Takaya, Shigeru; Arakawa, Hisashi*; Keyakida, Satoshi*
no journal, ,
A heat-resistant flux gate magnetic sensor has been developed. Permendur, which has high Curie temperature, is employed as the magnetic core material and the detection method of the external magnetic field is modified. The characteristics of the developed magnetic sensor at 300C were evaluated. The sensor output increases linearly with the external magnetic field in the range of 
5 G and the sensitivity is about 0.89 G.
Takaya, Shigeru; Arakawa, Hisashi*; Keyakida, Satoshi*
no journal, ,
A heat-resistant flux gate magnetic sensor has been developed. Permendur, which has high Curie point, is employed as the magnetic core material and the detection method of the external magnetic field is modified. The characteristics of the developed magnetic sensor up to 500C were evaluated. The sensor output increased linearly with the external magnetic field in the range of 5 G and the standard deviation at 500C was about 0.85G.
Takaya, Shigeru; Arakawa, Hisashi*; Keyakida, Satoshi*
no journal, ,
A hear-resistant magnetic sensor was newly developed. Permendur, a high Curie temperature material, was employed as a magnetic core material, and magnetic detection principle was modified by taking the magnetic property of Permendur into account. It was shown that sensor output is linear with respect to external magnetic field at least up to 500C, though sensitivity decreased slightly with temperature. Effect of oxidation of magnetic core was investigated, but it was concluded that oxidation of magnetic core is not major factor of decreasing in sensitivity.
