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Journal Articles

Constraint effect on fracture behavior of underclad crack in reactor pressure vessel

Shimodaira, Masaki; Tobita, Toru; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi

Journal of Pressure Vessel Technology, 144(1), p.011304_1 - 011304_7, 2022/02

 Times Cited Count:0 Percentile:0.00(Engineering, Mechanical)

In the structural integrity assessment of a reactor pressure vessel (RPV), the fracture toughness (K$$_{Jc}$$) should be higher than the stress intensity factor at the crack tip of an under-clad crack (UCC), which is prescribed in JEAC4206-2016. However, differences in crack depth and existence of cladding between the postulated crack and fracture toughness test specimens would be affected to the plastic constraint state and K$$_{Jc}$$ evaluation. In this study, we performed fracture toughness tests and finite element analyses (FEAs) to investigate the effect of cladding on K$$_{Jc}$$ evaluation. FEA showed that the cladding decreased the plastic constraint in the UCC rather than the surface crack. Moreover, it was also found that the apparent K$$_{Jc}$$ for the UCC was higher than that for the surface crack from tests and the local approach.

Journal Articles

Constraint effect on fracture mechanics evaluation for an under-clad crack in a reactor pressure vessel steel

Shimodaira, Masaki; Tobita, Toru; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi

Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 7 Pages, 2020/08

In JEAC 4206 which prescribes the methodology for assessing the structural integrity of reactor pressure vessels (RPVs), an under-clad crack (UCC) at the inner surface of RPV is postulated, and it is required that the fracture toughness of RPV steels is higher than stress intensity factor for at the crack tip during the pressurized thermal shock event. In the present study, to investigate the effect of cladding on the fracture toughness, we performed three-point bending fracture toughness tests and finite element analyses (FEAs) for an RPV steel containing an UCC or a surface crack, and the constraint effect for UCC was also discussed. As the result, we found that the fracture toughness for UCC was considerably higher than that for surface crack. On the other hand, the FEAs showed that the cladding decreased the constraint effect for UCC.

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:4 Percentile:40.00(Instruments & Instrumentation)

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

JAEA Reports

Confirmation tests for Warm Pre-stress (WPS) effect in reactor pressure vessel steel (Contract research)

Chimi, Yasuhiro; Iwata, Keiko; Tobita, Toru; Otsu, Takuyo; Takamizawa, Hisashi; Yoshimoto, Kentaro*; Murakami, Takeshi*; Hanawa, Satoshi; Nishiyama, Yutaka

JAEA-Research 2017-018, 122 Pages, 2018/03

JAEA-Research-2017-018.pdf:44.03MB

Warm pre-stress (WPS) effect is a phenomenon that after applying a load at a high temperature fracture does not occur in unloading during cooling, and then the fracture toughness in reloading at a lower temperature increases effectively. Engineering evaluation models to predict an apparent fracture toughness in reloading are established using experimental data with linear elasticity. However, there is a lack of data on the WPS effect for the effects of specimen size and surface crack in elastic-plastic regime. In this study, fracture toughness tests were performed after applying load-temperature histories which simulate pressurized thermal shock transients to confirm the WPS effect. The experimental results of an apparent fracture toughness tend to be lower than the predictive results using the engineering evaluation models in the case of a high degree of plastic deformation in preloading. Considering the plastic component of preloading can refine the engineering evaluation models.

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

Spin model of O$$_{2}$$-based magnet in a nanoporous metal complex

Soda, Minoru*; Homma, Yuki*; Takamizawa, Satoshi*; Kawamura, Seiko; Nakajima, Kenji; Masuda, Takatsugu*

Journal of the Physical Society of Japan, 85(3), p.034717_1 - 034717_9, 2016/03

 Times Cited Count:1 Percentile:11.30(Physics, Multidisciplinary)

Inelastic neutron scattering experiments are performed on the nanoporous metal complex Cu-${{it trans}}$-1,4-cyclohexanedicarboxylic acid (Cu-CHD) adsorbing O$$_{2}$$ molecules to identify the spin model of the O$$_{2}$$-based magnet realized in the host complex. It is found that the magnetic excitations of Cu-CHDs adsorbing low- and high-concentration O$$_{2}$$ molecules are explained by different spin models, the former by spin dimers and the latter by spin trimers. By using the obtained parameters and by assuming that the levels of the group of the highest energy states are reduced because of the nonnegligible spin dependence of the molecular potential of oxygen, the magnetization curves are explained quantitatively.

Journal Articles

Instability of magnons in two-dimensional antiferromagnets at high magnetic fields

Masuda, Takatsugu*; Kitaoka, Shuji*; Takamizawa, Satoshi*; Metoki, Naoto; Kaneko, Koji; Rule, K. C.*; Kiefer, K.*; Manaka, Hiroshi*; Nojiri, Hiroyuki*

Physical Review B, 81(10), p.100402_1 - 100402_4, 2010/00

 Times Cited Count:42 Percentile:81.23(Materials Science, Multidisciplinary)

Spin dynamics of the square lattice Heisenberg antiferromagnet, Ba$$_2$$MnGe$$_2$$O$$_7$$, is studied by a combination of bulk measurements, neutron diffraction, and inelastic neutron-scattering techniques. Easy plane type antiferromagnetic order is identified at T$$leq$$4.0 K. The exchange interactions are estimated as $$J_1$$ = 27.8(3) $$mu$$eV and$$J_2$$ = 1.0(1) $$mu$$eV, and the saturation field $$H$$$$_{rm C}$$ is 9.75 T. Magnetic excitation measurements with high experimental resolution setup by triple axis neutron spectrometer reveals the instability of one magnon excitation in the field range of 0.7$$H$$$$_{rm C}$$ $$_sim^{<}$$ $$H$$ $$_sim^{<}$$ 0.85$$H$$$$_{rm C}$$.

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

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

Study on reliability and predictability of Bayesian statistical analysis for irradiation embrittlement data

Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka

no journal, , 

no abstracts in English

Oral presentation

Statistical analysis on irradiation embrittlement data of Japanese RPV steels; Evaluation of influence factor on irradiation embrittlement

Takamizawa, Hisashi; 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

Solute cluster formation in heat-affected zone of ion-irradiated low alloy steel

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

no journal, , 

no abstracts in English

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

Statistical analysis on embrittlement factor in highly neutron irradiated RPV steels

Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka

no journal, , 

no abstracts in English

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

Microstructural analyses on Japanese RPV steels irradiated in PWR, 1; Effect of Cu and Si content on solute cluster formation

Takamizawa, Hisashi; Hata, Kuniki; Hanawa, Satoshi; Nishiyama, Yutaka; Toyama, Takeshi*; Nagai, Yasuyoshi*

no journal, , 

no abstracts in English

19 (Records 1-19 displayed on this page)
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