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Yano, Yasuhide; Tanno, Takashi; Oka, Hiroshi; Otsuka, Satoshi; Inoue, Toshihiko; Kato, Shoichi; Furukawa, Tomohiro; Uwaba, Tomoyuki; Kaito, Takeji; Ukai, Shigeharu*; et al.
Journal of Nuclear Materials, 487, p.229 - 237, 2017/04
Times Cited Count：51 Percentile：97.30(Materials Science, Multidisciplinary)Ultra-high temperature ring tensile tests were carried out to investigate the tensile behavior of oxide dispersion strengthened (ODS) steel claddings and wrapper materials under severe accident conditions; temperatures ranged from room temperature to 1400
C which is near the melting point of core materials. The experimental results showed that tensile strength of 9Cr-ODS steel claddings was highest in the core materials at the ultra-high temperatures between 900 and 1200C, but that there was significant degradation in tensile strength of 9Cr-ODS steel claddings above 1200C. This degradation was attributed to grain boundary sliding deformation with 
/
transformation, which was associated with reduced ductility. On the other hand, tensile strength of recrystallized 12Cr-ODS and FeCrAl-ODS steel claddings retained its high value above 1200 C unlike the other tested materials. Present study includes the result of "R&D of ODS ferritic steel fuel cladding for maintaining fuel integrity at the high temperature accident condition" entrusted to Hokkaido University by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).
Uwaba, Tomoyuki; Yano, Yasuhide; Otsuka, Satoshi; Naganuma, Masayuki; Tanno, Takashi; Oka, Hiroshi; Kato, Shoichi; Kaito, Takeji; Ukai, Shigeharu*; Kimura, Akihiko*; et al.
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04
Tolerance of fast rector fuel elements to failure in the typical accident conditions was evaluated for the oxide-dispersion-strengthened (ODS) ferritic steel claddings that are candidate of the cladding material for advanced fast reactors. The evaluation was based on the cladding creep damage, which was quantified by the cumulative damage fractions (CDFs). It was shown that the CDFs of the ODS ferritic steel cladding were substantially lower than the breach limit of 1.0 in the loss of flow and transient over power conditions until a passive reactor shutdown system operates.
Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji; Sakasegawa, Hideo*; Chikada, Nobuyoshi*; Hayashi, Shigenari*; Onuki, Somei*
Materials Science & Engineering A, 510-511, p.115 - 120, 2009/06
Times Cited Count：116 Percentile：96.46(Nanoscience & Nanotechnology)Oxide dispersion strengthened (ODS) ferritic steels, which are the most promising candidate materials for advanced fast reactor fuel elements, have exceptional creep strength at 973 K. The superior creep property of 9Cr-ODS ferritic steels is ascribed to the formation of a nonequilibrium phase, designated as the residual ferrite. The yield strength of the residual ferrite itself has been determined to be as high as 1360 MPa at room temperature from nanoindentation measurements. The creep strength is enhanced by minimizing the number of packet boundaries induced by the martensitic phase transformation. The creep strain occurs by sliding at weaker regions such as at the grain boundaries and packet boundaries. It is found that 9Cr-ODS ferritic steels behave as fiber composite materials comprising the harder residual ferrite and the softer tempered martensite.
Ukai, Shigeharu*; Onuki, Somei*; Hayashi, Shigenari*; Kaito, Takeji; Inoue, Masaki; Kimura, Akihiko*; Fujisawa, Toshiharu*; Okuda, Takanari*; Abe, Fujio*
Proceedings of 2009 International Congress on Advances in Nuclear Power Plants (ICAPP '09) (CD-ROM), p.9232_1 - 9232_7, 2009/05
The super ODS cladding were manufactured into 8.5 mm outer diameter and 0.5 mm thickness by using pilger.mill rolling and intermediate heat treatment. The final heat treatment was successfully conducted at 1150 C for 1h to make perfectly recrystallized structure. The manufactured cladding exhibits a secondary recrystallized grains with {110} 
100
Goss orientation. As a summary of super ODS steels R&D, the ODS steel, 16Cr-4Al-2W-0.1Ti added with small amount of Hf or Zr, is the prime candidate of "Super ODS steels" which has high strength at elevated temperatures, high resistance to corrosion for SCW and LBE, and high resistance to irradiation.
ferrite formation and high temperature tensile strength in 9Cr-ODS ferritic steelMiyata, Ryota*; Hayashi, Shigenari*; Ukai, Shigeharu*; Kaito, Takeji; Otsuka, Satoshi
no journal, ,
no abstracts in English
Leng, B.*; Hayashi, Shigenari*; Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
Kato, Shoichi; Furukawa, Tomohiro; Otsuka, Satoshi; Yano, Yasuhide; Inoue, Toshihiko; Kaito, Takeji; Kimura, Akihiko*; Torimaru, Tadahiko*; Hayashi, Shigenari*; Ukai, Shigeharu*
no journal, ,
In order to evaluate the fracture limit of the cladding material made by ODS at the severe accident condition, the mechanical strength tests have been performed at elevated temperature. In this meeting, the research plan and the progress on the mechanical strength under this research project is presented. In addition, the technical development result concerning the 1000C creep apparatus prepared for this research is also reported.
Yamamoto, Masahiro*; Hayashi, Shigenari*; Ukai, Shigeharu*; Kaito, Takeji; Otsuka, Satoshi
no journal, ,
JAEA has found out and proved that high-temperature strength of 9Cr-ODS steel is considerably improved by the formation of residual-alpha ferrite/martensite duplex microstructure. This study discussed the mechanism on residual-alpha ferrite formation using thermo-dynamic model.
Numata, Hiroya*; Hayashi, Shigenari*; Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
This study discussed the recrystallization mechanism from cold-worked texture in 12Cr-ODS ferritic steel.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
It may be possible that the high-temperature strength of 9Cr-ODS ferritic/martensitic steel is largely improved by the formation of ultra-fine residual-alpha phase. This study discussed the correlation between ultra-fine residual-alpha formation and mechanical strength in ODS ferritic steel.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
It may be possible that high-temperature strength of 9Cr-ODS ferritic/martensitic steel is largely improved by the ultra-fine residual-alpha phase. This study discussed the correlation between the ultra-fine residual alpha phase formation and mechanical strength.
Yamamoto, Masahiro*; Hayashi, Shigenari*; Ukai, Shigeharu*; Kaito, Takeji; Otsuka, Satoshi
no journal, ,
It may be possible that the high-temperature creep strength of 9Cr-ODS ferritic steel is largely improved by ultra-fine residual-alpha ferrite formation. This study discussed the mechanism on residual-alpha ferrite formation using thermodynamic model.
Ukai, Shigeharu*; Chikada, Nobuyoshi*; Hayashi, Shigenari*; Onuki, Somei*; Kaito, Takeji; Otsuka, Satoshi
no journal, ,
The 9Cr-ODS ferritic steel for fast reactor fuel cladding tube has been developed by JAEA. This study discussed the mechanism of high-temperature strength improvement produced by feeritic/martensitic duplex structure.
Yamamoto, Masahiro*; Hayashi, Shigenari*; Ukai, Shigeharu*; Kaito, Takeji; Otsuka, Satoshi; Osaki, Satoshi*; Azuma, Tsukasa*
no journal, ,
no abstracts in English
double-prime (Ni
Nb) in the high Ni steelSano, Keisuke*; Ono, Naoko*; Ukai, Shigeharu*; Hayashi, Shigenari*; Miura, Seiji*; Yamashita, Shinichiro; Inoue, Toshihiko
no journal, ,
no abstracts in English
double-prime (NiNb) in the high Ni steelSano, Keisuke*; Ono, Naoko*; Ukai, Shigeharu*; Hayashi, Shigenari*; Miura, Seiji*; Yamashita, Shinichiro; Inoue, Toshihiko
no journal, ,
JAEA is study in the high Ni-alloy behavior as ODS substitute materials for the use in fast reactor. The precipitation behavior of double-prime (NiNb) in the high Ni steel was tested in prescription examinations. The results was the double-prime (NiNb) became a fault size and the hardness was decreased in the high prescription temperature and the long prescription time.
Yano, Yasuhide; Kato, Shoichi; Otsuka, Satoshi; Inoue, Toshihiko; Tanno, Takashi; Oka, Hiroshi; Furukawa, Tomohiro; Kaito, Takeji; Kimura, Akihiko*; Torimaru, Tadahiko*; et al.
no journal, ,
no abstracts in English
Kato, Shoichi; Furukawa, Tomohiro; Yano, Yasuhide; Tanno, Takashi; Otsuka, Satoshi; Oka, Hiroshi; Inoue, Toshihiko; Kaito, Takeji; Ukai, Shigeharu*; Kimura, Akihiko*; et al.
no journal, ,
Oxide dispersion strengthened (ODS) steel is a prime candidate for cladding tubes of Japan Sodium-cooled Fast Reactor (JSFR) due to the high temperature and radiation resistances. One of the safety design of JSFR for Design Extension Condition (DEC) is the control of severe plant conditions, including prevention of severe accidents and mitigation of severe-accident consequences. Therefore, it is necessary to acquire the mechanical properties at ultra-high temperature conditions for core materials to evaluate safety design. There are, however, no data for ODS claddings at ultra-high temperature condition for the reflecting to the design criteria. In this study, creep rupture tests of 9Cr-ODS, 12Cr-ODS and FeCrAl-ODS steel claddings have been done at elevated temperatures, and the effect of minor elements such as Al, Zr and O on the mechanical strength and the creep rupture curve for the safety design were evaluated. The effect of minor elements was estimated based on the data at 700C and 1000C. As the results, it was confirmed that the addition of Zr had an effect on the improvement of creep strength at elevated temperature for the FeCrAl-ODS steel claddings.
Hashimoto, Naoyuki*; Ueda, Mikito*; Hayashi, Shigenari*; Oka, Hiroshi*; Isobe, Shigehito*; Yamashita, Shinichiro; Itakura, Mitsuhiro; Tsuru, Tomohito
no journal, ,
The objective of this work is the development of new reduced activation HEAs applicable to next generation small module reactor components by using additive manufacturing (3D printing) method under the support of the 2020 MEXT Innovative Nuclear Research and Development Program. We firstly introduce the outline of this work as a part of the series presentation.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Onuki, Somei*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
The hardness measurement by nanoindentation and microstructure analysis by TEM revealed that the tempering softening resistance of 9Cr-ODS ferritic steels is owing to the formation of ultrafine grains in residual ferrite phase.
