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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
) 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 evaluation. In this study, we performed fracture toughness tests and finite element analyses (FEAs) to investigate the effect of cladding on K 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 for the UCC was higher than that for the surface crack from tests and the local approach.
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.
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)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
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.
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
-based magnet in a nanoporous metal complexSoda, 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-
-1,4-cyclohexanedicarboxylic acid (Cu-CHD) adsorbing O molecules to identify the spin model of the O-based magnet realized in the host complex. It is found that the magnetic excitations of Cu-CHDs adsorbing low- and high-concentration O 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.
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
MnGeO
, is studied by a combination of bulk measurements, neutron diffraction, and inelastic neutron-scattering techniques. Easy plane type antiferromagnetic order is identified at T
4.0 K. The exchange interactions are estimated as 
= 27.8(3) 
eV and
= 1.0(1) eV, and the saturation field 
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 
0.85.
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.
Ha, Yoosung; Iwata, Keiko; Takamizawa, Hisashi; Okamoto, Yoshihiro; Shimoyama, Iwao; Honda, Mitsunori; Hanawa, Satoshi; Nishiyama, Yutaka
no journal, ,
no abstracts in English
Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka
no journal, ,
no abstracts in English
Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka
no journal, ,
no abstracts in English
Ha, Yoosung; Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka
no journal, ,
no abstracts in English
Ha, Yoosung; Iwata, Keiko; Takamizawa, Hisashi; Okamoto, Yoshihiro; Honda, Mitsunori; Hanawa, Satoshi; Nishiyama, Yutaka
no journal, ,
no abstracts in English
Ha, Yoosung; Iwata, Keiko; Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka
no journal, ,
no abstracts in English
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.
Takamizawa, Hisashi; Hanawa, Satoshi; Nishiyama, Yutaka
no journal, ,
no abstracts in English
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.
Takamizawa, Hisashi; Hata, Kuniki; Hanawa, Satoshi; Nishiyama, Yutaka; Toyama, Takeshi*; Nagai, Yasuyoshi*
no journal, ,
no abstracts in English
