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Journal Articles

Fracture toughness in postulated crack area of PTS evaluation in highly-neutron irradiated RPV steel

Ha, Yoosung; Shimodaira, Masaki; Takamizawa, Hisashi; Tobita, Toru; Katsuyama, Jinya; Nishiyama, Yutaka

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07

Journal Articles

Assessment of residual stress for thick butt-welded plate of a reactor pressure vessel steel

Ha, Yoosung; Okano, Shigetaka*; Takamizawa, Hisashi; Katsuyama, Jinya; Mochizuki, Masahito*

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07

Journal Articles

Ion-induced irradiation hardening of the weld heat-affected zone in low alloy steel

Ha, Yoosung; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi; Nishiyama, Yutaka

Nuclear Instruments and Methods in Physics Research B, 461, p.276 - 282, 2019/12

 Times Cited Count:0 Percentile:0.02(Instruments & Instrumentation)

Journal Articles

Study on irradiation hardening mechanism of RPV steel; Experiments for irradiation temperature control

Ha, Yoosung; Shimodaira, Masaki; Tobita, Toru; Hanawa, Satoshi; Yamasaki, Shota*; Uno, Sadanori*

2018-Nendo Ryoshi Kagaku Gijutsu Kenkyu Kaihatsu Kiko Shisetu Kyoyo Jisshi Hokokusho (Internet), 3 Pages, 2019/09

no abstracts in English

Journal Articles

Susceptibility to neutron irradiation embrittlement of heat-affected zone of reactor pressure vessel steels

Takamizawa, Hisashi; Katsuyama, Jinya; Ha, Yoosung; Tobita, Toru; Nishiyama, Yutaka; Onizawa, Kunio

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 8 Pages, 2019/07

no abstracts in English

Journal Articles

Applicability of miniature compact tension specimens for fracture toughness evaluation of highly neutron irradiated reactor pressure vessel steels

Ha, Yoosung; Tobita, Toru; Otsu, Takuyo; Takamizawa, Hisashi; Nishiyama, Yutaka

Journal of Pressure Vessel Technology, 140(5), p.051402_1 - 051402_6, 2018/10

 Times Cited Count:1 Percentile:11.36(Engineering, Mechanical)

Journal Articles

Fracture toughness evaluation of heat-affected zone under weld overlay cladding in reactor pressure vessel steel

Ha, Yoosung; Tobita, Toru; Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka

Proceedings of 2018 ASME Pressure Vessels and Piping Conference (PVP 2018), 6 Pages, 2018/07

Journal Articles

Microstructure analysis using X-ray absorption on heat-affected zone of reactor pressure vessel steel

Iwata, Keiko; Takamizawa, Hisashi; Ha, Yoosung; Okamoto, Yoshihiro; Shimoyama, Iwao; Honda, Mitsunori; Hanawa, Satoshi; Nishiyama, Yutaka

Photon Factory Activity Report 2017, 2 Pages, 2018/00

no abstracts in English

Journal Articles

Fracture toughness evaluation of neutron-irradiated reactor pressure vessel steel using miniature-C(T) specimens

Ha, Yoosung; Tobita, Toru; Takamizawa, Hisashi; Nishiyama, Yutaka

Proceedings of 2017 ASME Pressure Vessels and Piping Conference (PVP 2017) (CD-ROM), 5 Pages, 2017/07

The applicability of miniature-C(T) (Mini-C(T)) specimens to fracture toughness evaluation was investigated for neutron-irradiated reactor pressure vessel (RPV) steel. $$T_{o}$$ value determined from irradiated Mini-C(T) specimens was in good agreement with that determined from the irradiated pre-cracked Charpy-type (PCCv) specimens. Also, the scatter of the 1T-equivalent fracture toughness values obtained from the irradiated Mini-C(T) specimens was not significantly different from that obtained from the irradiated PCCv. $$T_{o}$$ values determined from Mini-C(T) specimens agreed very well with the correlation between Charpy 41J transition temperature and $$T_{o}$$ of commercially manufactured RPV steels.

Oral presentation

Microstructure analysis on thermally aged stainless overlay cladding using X-ray absorption

Iwata, Keiko; Takamizawa, Hisashi; Ha, Yoosung; Okamoto, Yoshihiro; Shimoyama, Iwao; Kojima, Hiroshi*; Mayumi, Ren*; Iwase, Akihiro*; Nagai, Yasuyoshi*; Nishiyama, Yutaka

no journal, , 

Microstructure analysis for thermally aged stainless overlay cladding was conducted by using X-ray absorption. X-ray absorption fine structure analysis was adapted, which was possible to obtain the average information of a material and to identify the bond length and chemical state by the selected atoms. In this study, changes of coordination number and bond length around the Mn atom were recognized.

Oral presentation

The Correlation between microstructure and ion irradiation hardening in heat affected zone of reactor pressure vessel

Ha, Yoosung; Takamizawa, Hisashi; Iwata, Keiko; Tobita, Toru; Chimi, Yasuhiro; Katsuyama, Jinya; Nishiyama, Yutaka

no journal, , 

The microstructure of heat affected zone (HAZ) in stainless over-ray clad is predicted by finite element method (FEM). From the results of FEM analysis, the coarse grain area and fine grain area could obtain from HAZ and base metal also obtained in 1/4 thickness part for the irradiation experiment. After ion irradiation, the irradiation hardening of HAZ has higher tendency than that of base metal. In addition, the change of hardening is observed in fine grain area.

Oral presentation

Microstructure and hardening of ion-irradiated heat-affected zone of reactor pressure vessel steel

Ha, Yoosung; Takamizawa, Hisashi; Katsuyama, Jinya; Nishiyama, Yutaka; Yoshida, Kenta*; Toyama, Takeshi*; Nagai, Yasuyoshi*

no journal, , 

Heat-affected zone of stainless over-ray clad is included in a supposed cracking area during the pressurized thermals shock regime. It is necessary to confirm the irradiation embrittlement susceptibility of HAZ compared with that of matrix. In this study, Fe$$^{2+}$$ ion irradiated into HAZ and matrix. We discussed the correlation between irradiation hardening and microstructure in HAZ. The irradiation hardening of SCFGHAZ is highest. As results of TEM observation, the precipitates dispersed with ~200 nm of sizes in SCFGHAZ specimen. Also, dislocation loops with high density by irradiation exist.

Oral presentation

Ion irradiation-induced microstructural changes in heat-affected zone of stainless weld overlay cladding of RPV steel

Ha, Yoosung; Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka; Ebisawa, Naoki*; Toyama, Takeshi*; Nagai, Yasuyoshi*

no journal, , 

Heat affected zone (HAZ) under stainless overlay cladding of RPV steel was irradiated by iron ions. To investigate the mechanism of irradiation hardening, the solute clusters distributions were confirmed by 3D-Atom Probe Tomography analysis, and the correlation between the irradiation hardening and the microstructure change in HAZ and matrix was discussed. As result of APT analysis, Cu and Si-Mn-Ni clusters were observed in irradiated area, but not in un-irradiated area. The distributions of cluster were different in coarse grain HAZ, fine grain HAZ and matrix, and the amounts of clusters in matrix were significantly lower than that in HAZ. In addition, size, chemical composition and number densities of clusters and their distributions were correlated with irradiation hardening.

Oral presentation

Effect of ion irradiation on microstructural change and hardening in HAZ under weld overlay cladding of RPV

Ha, Yoosung; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi; Nishiyama, Yutaka; Yoshida, Kenta*; Toyama, Takeshi*; Nagai, Yasuyoshi*

no journal, , 

This talk will present the effect of ion irradiation on heat affected zone (HAZ) of stainless overlay cladding in RPV steels. After ion-irradiation, microstructural changes of HAZ were observed by TEM and APT. We confirmed the distributions of precipitates and solute clusters in both HAZ and base metal. Correlation between irradiation hardening and microstructural changes will be discussed in this study.

Oral presentation

Ion irradiation effect on micro structures of heat affected zone under stainless overlay clad in RPV steel

Ha, Yoosung; Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka; Ebisawa, Naoki*; Yoshida, Kenta*; Toyama, Takeshi*; Nagai, Yasuyoshi*

no journal, , 

Stainless overlay clad is welded on the inner surface of the reactor pressure vessel steel to prevent corrosion by the primary coolant. Heat affected zone (HAZ) is created during the welding and the micro structure at the HAZ is different from that of the base metal. This microstructural difference would cause the difference in irradiation hardening as well as embrittlement between the HAZ and the base metal. In order to confirm the irradiation embrittlement susceptibility of HAZ, Fe2+ ion irradiation experiment was carried out to both the HAZ and the base metal in this study. As results of TEM observation, precipitates dispersed with the size of ~200 nm in SCFGHAZ. Also, finer and higher number density of solute clusters were observed in the HAZ than that of the base metal by the atom prove tomography analysis. It was considered that the higher irradiation hardening of HAZ was caused by the precipitates and these solute clusters.

Oral presentation

JAEA research on the structural integrity assessment of reactor pressure vessel for safe long-term operation; Fracture toughness evaluation

Ha, Yoosung; Takamizawa, Hisashi; Tobita, Toru; Nishiyama, Yutaka

no journal, , 

no abstracts in English

Oral presentation

Microstructure analysis using X-ray absorption on HAZ of ion-irradiated RPV steel

Ha, Yoosung; Iwata, Keiko; Takamizawa, Hisashi; Okamoto, Yoshihiro; Shimoyama, Iwao; Honda, Mitsunori; Hanawa, Satoshi; Nishiyama, Yutaka

no journal, , 

no abstracts in English

Oral presentation

Microstructural change of heat-affected zone under stainless overlay cladding of RPV steel irradiated with ions

Ha, Yoosung; Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka

no journal, , 

no abstracts in English

Oral presentation

Ion-induced microstructural change of A533B steel analyzed by X-ray absorption fine structure spectroscopy

Ha, Yoosung; Iwata, Keiko; Takamizawa, Hisashi; Okamoto, Yoshihiro; Honda, Mitsunori; Hanawa, Satoshi; Nishiyama, Yutaka

no journal, , 

no abstracts in English

Oral presentation

Effect of microstructure on fracture toughness of un-irradiated and irradiated heat affected zone materials of RPV steels

Katsuyama, Jinya; Takamizawa, Hisashi; Ha, Yoosung; Nishiyama, Yutaka; Onizawa, Kunio

no journal, , 

We will present microstructure analysis results obtained by SEM and APT and so on for heat affected zone (HAZ) materials. The effects of microstructures such as grain size, phase fraction and martensite-austenite constituent on fracture toughness of HAZ materials were investigated. Also, the effects of solute cluster in the matrix and segregation near the carbide on irradiation embrittlement susceptibility will be discussed.

28 (Records 1-20 displayed on this page)