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Iwata, Keiko; Takamizawa, Hisashi; Ha, Yoosung; Shimodaira, Masaki; Okamoto, Yoshihiro; Honda, Mitsunori; Katsuyama, Jinya; Nishiyama, Yutaka
Nuclear Instruments and Methods in Physics Research B, 511, p.143 - 152, 2022/01
Times Cited Count：1 Percentile：33.4(Instruments & Instrumentation)Iwata, Keiko; Hata, Kuniki; Tobita, Toru; Hirota, Takatoshi*; Takamizawa, Hisashi; Chimi, Yasuhiro; Nishiyama, Yutaka
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 7 Pages, 2021/07
-rays after neutron capture by 
La for a T-violation searchOkudaira, Takuya; Shimizu, Hirohiko*; Kitaguchi, Masaaki*; Hirota, Katsuya*; Haddock, C. C.*; Ito, Ikuya*; Yamamoto, Tomoki*; Endo, Shunsuke*; Ishizaki, Kohei*; Sato, Takumi*; et al.
EPJ Web of Conferences, 219, p.09001_1 - 09001_6, 2019/12
Parity violating effects enhanced by up to 10
times have been observed in several neutron induced compound nuclei. There is a theoretical prediction that time reversal (T) violating effects can also be enhanced in these nuclei implying that T-violation can be searched for by making very sensitive measurements. However, the enhancement factor has not yet been measured in all nuclei. The angular distribution of the (n,) reaction was measured with La by using a germanium detector assembly at J-PARC, and the enhancement factor was obtained. From the result, the measurement time to achieve the most sensitive T-violation search was estimated as 1.4 days, and a 40% polarized La target and a 70% polarized 
He spin filter whose thickness is 70 atm
cm are needed. Therefore high quality He spin filter is developed in JAEA. The measurement result of the (n,) reaction at J-PARC and the development status of the He spin filter will be presented.
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
Chimi, Yasuhiro; Takamizawa, Hisashi; Kasahara, Shigeki*; Iwata, Keiko; Nishiyama, Yutaka
Nuclear Engineering and Design, 307, p.411 - 417, 2016/10
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)To investigate influential parameters for irradiation-assisted stress corrosion cracking (IASCC) growth behavior, we attempt to analyze statistically existing data on the crack growth rate (CGR) in irradiated austenitic stainless steels (SSs) in boiling water reactor (BWR) environments using the Bayesian nonparametric (BNP) method. From the probability distribution of CGR and some input parameters, such as yield stress of irradiated material (
), stress intensity factor (
), electrochemical corrosion potential (ECP), and fast neutron fluence, the mean CGR is estimated and compared with the measured CGR. The analytical results show good reproducibility of the measured CGR. The results also indicate the possible neutron fluence effects on CGR in high CGR region (i.e., high neutron fluence condition) by radiation-induced segregation (RIS), localized deformation, and/or other mechanisms than radiation hardening.
Iwata, Keiko; Tobita, Toru; Takamizawa, Hisashi; Chimi, Yasuhiro; Yoshimoto, Kentaro*; Nishiyama, Yutaka
Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 6 Pages, 2016/07
The effect of warm pre-stressing (WPS) on fracture toughness was evaluated for a reactor pressure vessel steel. Various types of thermomechanical loadings were applied to 1T-CT specimens. The results were compared with predictions from several analytical WPS engineering models. The specimen size effect was subsequently investigated under the load-unload-cool-fracture transient condition using 1T-, 0.4T-, and 0.16T-CT specimens. Analyses of the plastic zone distribution and residual stress were conducted to identify the difference in the WPS effect among the specimens.
Takahashi, Satoru*; Okuda, Yasutake*; Kawabata, Kuniaki; Aonuma, Hitoshi*; Sato, Yutaka*; Iwata, Kenji*
Journal of Signal Processing, 20(2), p.65 - 74, 2016/03
decay of 
CaIwata, Yoritaka*; Shimizu, Noritaka*; Otsuka, Takaharu*; Utsuno, Yutaka; Men
ndez, J.*; Homma, Michio*; Abe, Takashi*
Physical Review Letters, 116(11), p.112502_1 - 112502_6, 2016/03
Times Cited Count：81 Percentile：94.57(Physics, Multidisciplinary)no abstracts in English
Nunoshiba, Tatsuo*; Yamauchi, Ayako*; Iwata, Rika*; Sato, Katsuya; Ono, Yutaka; Narumi, Issey*
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 124, 2015/03
Isobe, Motoyasu; Kameo, Yutaka; Nakashio, Nobuyuki; Wakui, Takuji*; Iwata, Keiji*; Kibayashi, Tatsuyuki*; Kanazawa, Katsuo; Nakashima, Mikio; Hirabayashi, Takakuni*
JAERI-Tech 2000-049, 29 Pages, 2000/09
JAERI-Tech-2000-049.pdf:2.87MB
no abstracts in English
ray radiography using a multi-color converterIwata, Hideki*; Mochiki, Koichi*; Murata, Yutaka*; Nitto, Koichi*; Tamura, Toshiyuki*; Kobayashi, Hisao*; Matsubayashi, Masahito
Dai-3-Kai Hoshasen Ni Yoru Hihakai Hyoka Shimpojiumu Koen Rombunshu, p.142 - 147, 1999/11
no abstracts in English
Tsuji, Hirokazu; ; Fujita, Mitsutane*; Kurihara, Yutaka*; Kano, Shigeki*; Tachi, Yoshiaki*; Shimura, Kazuki*; Nakajima, Ritsuko*; Iwata, Shuichi*
Journal of Nuclear Materials, 271-272, p.486 - 490, 1999/00
no abstracts in English
Shimura, Kazuki*; Nakajima, Ritsuko*; Fujita, Mitsutane*; Kurihara, Yutaka*; Tsuji, Hirokazu; ; Tachi, Yoshiaki*; Kano Shigeki*; Iwata, Shuichi*
JAERI-Tech 97-047, 22 Pages, 1997/10
no abstracts in English
Ueno, Fumiyoshi; Kano, Shigeki; Fujita, Mitsutane*; Kurihara, Yutaka*; Nakajima, Hajime*; Yokoyama, Norio*; Iwata, Shuichi*
Journal of Nuclear Science and Technology, 31(12), p.1314 - 1324, 1994/00
None
Asahina, Kiyoshi*; Soya, Masataka*; Ogawa, Hikaru*; Akasaka, Takayuki*; Iwata, Toshio*; Fukutome, Yutaka*; Nakayama, Jumpei*
PNC TJ4058 89-005, 178 Pages, 1989/06
None
Aoyama, Takafumi; Ito, Chikara; Araki, Yoshio; Naito, Hiroyuki; Iwata, Yoshihiro; Okazaki, Koki*; Harano, Hideki*; Watanabe, Kenichi*; Iguchi, Tetsuo*; Takegawa, Nobuyuki*; et al.
no journal, ,
no abstracts in English
Aoyama, Takafumi; Ito, Chikara; Naito, Hiroyuki; Iwata, Yoshihiro; Harano, Hideki*; Okazaki, Koki*; Araki, Yoshio*; Watanabe, Kenichi*; Iguchi, Tetsuo*; Takegawa, Nobuyuki*; et al.
no journal, ,
no abstracts in English
Kaji, Yoshiyuki; Nemoto, Yoshiyuki; Takase, Kazuyuki; Tojo, Masayuki*; Goto, Daisuke*; Iwata, Yutaka*; Otake, Yukihiko*; Nishimura, Satoshi*; Suzuki, Hiroaki*
no journal, ,
We will make quantitatively clear the phenomenon of fuel air oxidation mechanism, fuel failure mechanism after loss of coolant and criticality risks during and after sever accidents of Spent Fuel Pool(SFP) and clarify the quantitative effects of enhancements of SFP safety such as Spray and fuel loading patterns. We will report the whole plan in this presentation.
Chitose, Hiromasa*; Watanabe, Satoshi*; Sadamatsu, Hideaki*; Iwata, Yutaka*; Kaji, Yoshiyuki; Nemoto, Yoshiyuki
no journal, ,
We researched the recent enhancements of regulations and solutions related Spent Fuel Pool safety and reported the analytical results about problems and evaluation procedures related effectiveness evaluation of safety measures.
