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Hata, Kuniki; Takamizawa, Hisashi; Hojo, Tomohiro*; Ebihara, Kenichi; Nishiyama, Yutaka; Nagai, Yasuyoshi*
Journal of Nuclear Materials, 543, p.152564_1 - 152564_10, 2021/01
Times Cited Count：12 Percentile：91.16(Materials Science, Multidisciplinary)Reactor pressure vessel (RPV) steels for pressurized water reactors (PWRs) with bulk P contents ranging from 0.007 to 0.012wt.% were subjected to neutron irradiation at fluences ranging from 0.3 to 1.2
10
n/cm
(E 
1 MeV) in PWRs or a materials testing reactor (MTR). Grain-boundary P segregation was analyzed using Auger electron spectroscopy (AES) on intergranular facets and found to increase with increasing neutron fluence. A rate theory model was also used to simulate the increase in grain-boundary P segregation for RPV steels with a bulk P content up to 0.020wt.%. The increase in grain-boundary P segregation in RPV steel with a bulk P content of 0.015wt.% (the maximum P concentration found in RPV steels used in Japanese nuclear power plants intended for restart) was estimated to be less than 0.1 in monolayer coverage at 1.010 n/cm (E 1 MeV). A comparison of the PWR data with the MTR data showed that neutron flux had no effect upon grain-boundary P segregation. The effects of grain-boundary P segregation upon changes in irradiation hardening and ductile-brittle transition temperature (DBTT) shifts were also discussed. A linear relationship between irradiation hardening and the DBTT shift with a slope of 0.63 obtained for RPV steels with a bulk P content up to 0.026wt.%, which is higher than that of most U.S. A533B steels. It is concluded that the intergranular embrittlement is unlikely to occur for RPV steels irradiated in PWRs.
Ueno, Fumiyoshi; Komatsu, Atsushi; Igarashi, Takahiro; Yamamoto, Masahiro
Proceedings of European Corrosion Congress 2014 (EUROCORR 2014) (USB Flash Drive), 10 Pages, 2014/09
In this paper, the effect of phosphorous concentration in grain boundary (GB) on intergranular corrosion (IC) progress was studied to understand GB corrosion behavior of stainless steels in boiling nitric acid solution. Phosphorus (P) added extra high purity type 310 stainless alloy was corroded in boiling nitric acid solution, and P in GB was detected by three-dimensional atom probe. IC progress considering with P profile in GB was studied by numerical simulation using cellular automaton method. As the results, we concluded that P concentration change around 1.4at% in GB of the alloy caused IC rate change in boiling nitric acid solution. The developed numerical method could simulate GB corrosion change with P distribution in GB.
Tsukada, Takashi
Nihon Yosetsu Kyokai "Genshiryoku Kozo Kiki No Zairyo, Sekkei, Seko, Kensa Ni Kansuru Koshukai" Tekisuto, 40 Pages, 2002/00
no abstracts in English
; Yamagata, Ichiro; Donomae, Takako; Akasaka, Naoaki
JNC TN9400 2000-046, 24 Pages, 2000/02
lt is well known that solute atoms are segregated on surface, grain boundary, etc. and composition changed partially in irradiated austenitic stainless steel. For understanding radiation induced segregation (RIS), we adopt a Fe-15Cr-20Ni-x (x: Si, Mo) which is basically alloy system in PNC1520, and size of Si, Mo are different from matrix atoms to investigate RIS behaviors. The specimens were irradiated by "Joyo" fast reactor that irradiation condition is 3.5 10
n/m (E>0.1Mev) at 476
C. After irradiation, the specimen were observed and analyzed with EDS (Energy Dispersive X-ray Spectroscope) of 400kV TEM (Transmission Electron Microscope). The behavior of RIS depends on size of solute atoms of alloy. For example, oversized atoms are decreased and undersized atoms are increased in sink. RIS of voids are as same as or more than grain boundaries and smaller than precipitates. The void denuded zone was existed nearby G.B. in case of combinations between the grains from G.B.0ne of the reasons in this, the voids swepted by moving G.B. in radiation induced G.B. migration.
; ; ;
JAERI-M 9150, 30 Pages, 1980/10
no abstracts in English
Ebihara, Kenichi; Suzudo, Tomoaki; Yamaguchi, Masatake
no journal, ,
Phosphorus (P) atoms bring about grain boundary (GB) embrittlement in steel materials and can influence the rise of ductile-brittle transition temperature in reactor pressure vessel steels. Thus, a rate theory model for analyzing irradiation-induced GB P segregation is developed based on the atomistic processes. So far, we have incorporated the trapping process to the model based on the result of molecular dynamics (MD) simulations. However, the conventional model is used for the trapping process. In this study, we simulated the migration of a P atom in a GB. In addition, based on the consideration of the MD results, we modified the de-trapping model and applied the rate theory model to the temperature dependence of irradiation-induced GB P segregation. It was found that P atoms migrate through a gap in the GB region. In the calculated GB P segregation, the GB P coverage increased at T 600C and that the increase depended on the GB P segregation energy.
Hata, Kuniki; Nagai, Yasuyoshi*; Nishiyama, Yutaka
no journal, ,
no abstracts in English
Hata, Kuniki
no journal, ,
no abstracts in English
