Creep deformation and rupture behavior of 9Cr-ODS steel cladding tube at high temperatures from 700C to 1000C

Imagawa, Yuya; Hashidate, Ryuta; Miyazawa, Takeshi; Onizawa, Takashi; Otsuka, Satoshi; Yano, Yasuhide; Tanno, Takashi; Kaito, Takeji; Onuma, Masato*; Mitsuhara, Masatoshi*; et al.

Journal of Nuclear Science and Technology, 61(6), p.762 - 777, 2024/06

https://doi.org/10.1080/00223131.2023.2269178

The Japan Atomic Energy Agency has been developing 9Cr-oxide dispersion strengthened (ODS) steel as a fuel cladding material for sodium-cooled fast reactors (SFRs). Previous studies have formulated the creep rupture equation for 650C to 850C. However, little data have been obtained above 850C, and no equation has been formulated. This study conducted creep tests to evaluate creep strength at 700C to 1000C. Two creep test methods, the internal pressure and ring creep tests under development, were used, and the validation of the ring creep test method was conducted. The results showed that 9Cr-ODS steel undergoes almost no strength change due to the matrix's phase transformation, and a single equation can express a creep rupture strength from 700C to 1000C. In validating the ring creep test method, analysis clarified the effect of stress concentration on the specimen. Plastic deformation occurs at high initial stress and may lead to early rupture. The results will be essential for future creep testing and evaluation of neutron-irradiated 9Cr-ODS steel.

FBR metallic materials test manual (2023 revised edition)

Imagawa, Yuya; Toyota, Kodai; Onizawa, Takashi; Kato, Shoichi

JAEA-Testing 2023-004, 76 Pages, 2024/03

JAEA-Testing-2023-004.pdf:2.08MB

This manual describes the methods for conducting material tests in air, argon gas, and sodium, and for organizing the data obtained, as a part of the development of high-temperature structural design technology for fast reactors. This manual reflects the revision of test methods in Japanese Industrial Standards (JIS) to the "FBR Metallic Materials Test Manual, PNC TN241 77-03" published in 1977 and the "FBR Metallic Materials Test Manual (Revised Edition), JNC TN9520 2001-001" published in 2001. Also, it was written with reference to the recommended room temperature / elevated temperature tensile test method by the Japan Society of Mechanical Engineers (JSME) and the test standard for the elevated-temperature low-cycle fatigue test method by the Society of Materials Science, Japan (JSMS), which are the standard for material test methods in the domestic academic society.

High-temperature creep properties of 9Cr-ODS tempered martensitic steel and quantitative correlation with its nanometer-scale structure

Otsuka, Satoshi; Shizukawa, Yuta; Tanno, Takashi; Imagawa, Yuya; Hashidate, Ryuta; Yano, Yasuhide; Onizawa, Takashi; Kaito, Takeji; Onuma, Masato*; Mitsuhara, Masatoshi*; et al.

Journal of Nuclear Science and Technology, 60(3), p.288 - 298, 2023/03

https://doi.org/10.1080/00223131.2022.2096147

JAEA has been developing 9Cr-oxide dispersion strengthened (ODS) tempered martensitic steel(TMS) as a candidate material for the fuel cladding tubes of sodium-cooled fast reactors(SFRs). The reliable prediction of in-reactor creep-rupture strength is critical for implementing the 9Cr-ODS TMS cladding tube in the SFR. This study investigated the quantitative correlation between the creep properties of 9Cr-ODS TMS at 700 C and the dispersions of nanosized oxides by analyzing the creep data and the material's nanostructure. The possibility of deriving a formula for estimating the in-reactor creep properties of 9Cr-ODS TMSs based on an analysis of the nanostructure of neutron-irradiated 9Cr-ODS TMSs was also discussed. The creep properties of 9Cr-ODS TMS at 700 C closely correlated with the dispersion of nanosized oxide particles. The correlation between creep-rupture lives and nanosized oxide particle dispersion was determined using existing creep models. The elucidation of correlation between the stress exponent of secondary creep rate and the nanostructure is essential to enhance future modeling reliability and formulation.

Document collection of the 30th Technical Special Committee on Fugen Decommissioning

Kutsuna, Hideki; Koda, Yuya; Imagawa, Yasuhiro

JAEA-Review 2014-045, 38 Pages, 2015/01

JAEA-Review-2014-045.pdf:67.33MB

Fugen Decommissioning Engineering Center, in planning and carrying out our decommissioning technical development, has been establishing "Technical special committee on Fugen decommissioning" which consists of the members well-informed, aiming to make good use of Fugen as a place for technological development which is opened inside and outside the country, as the central point in the energy research and development base making project of Fukui prefecture, and to utilize the outcome in our decommissioning to the technical development effectively. This report compiles presentation materials "The Current Situation of Fugen Decommissioning", "Evaluation for Dismantlement Work Experience on Turbine System and its Future Plan" and "Completion of Taking-Out Heavy Water from Fugen", presented in the 30th Technical special committee on Fugen decommissioning which was held on September 19, 2014.

Thermal aging effects on high temperature tensile properties of Mod.9Cr-1Mo steel

Toyota, Kodai; Imagawa, Yuya; Onizawa, Takashi

no journal, , 

no abstracts in English

Development of the material strength standard of 316FR steel and modified 9Cr-1Mo steel for next-generation fast reactor in Japan

Onizawa, Takashi; Toyota, Kodai; Imagawa, Yuya; Okajima, Satoshi; Ando, Masanori

no journal, , 

In order to realize a fast reactor that achieves both safety and economic efficiency at a high level, Japan Atomic Energy Agency (JAEA) is developing the material strength standard for fast reactor design. JAEA has developed the material strength standard based on the acquired data and its evaluation results, and the standard have been incorporated in the Japan Society of Mechanical Engineers (JSME) code, Rules on the Design and Construction of Nuclear Power Plants, Section II, Fast Reactors (JSME D&C FRs Code). This paper describes the standard that recently incorporated in the JSME D&C FRs code and ongoing studies for improvements in the near future.

Evaluation of failure lives of mod. 9Cr-1Mo steel under high temperature multiaxial creep-fatigue using strain energy; Effect of maximum stress history and stress relaxation on life correlation

Ogawa, Fumio*; Imagawa, Yuya; Hashidate, Ryuta; Hiyoshi, Noritake*; Ito, Takamoto*

no journal, , 

In recent years, the demand for environmental protection has led to a trend toward shorter startup and shutdown intervals in thermal power plants. In fast breeder reactors (FBRs), more stringent operating environments (temperature and sodium environment) are also being considered. Modified 9Cr-1Mo steel is used in thermal power plants and fast breeder reactors because of its excellent mechanical properties at high temperatures. In actual machines, Modified 9Cr-1Mo steel is used in a creep-fatigue type with complex stress conditions, which may cause more damage than the uniaxial condition, so it is necessary to measure the multiaxial creep-fatigue life and establish a life evaluation method. In this study, axial and torsional multiaxial creep-fatigue tests were conducted in 550C air to accumulate property data and to evaluate the life. The results will be described later, but the strain rate and retention time dependence showed peculiarities different from those in the past. Next, the strain energy corresponding to the hysteresis loop area between stress and strain was calculated to evaluate the life, and the same energy was theorized to compare the actual and theoretical life. Specifically, a new life evaluation method based on strain energy was studied, which can evaluate the peculiar strain rate, retention time dependence, and multiaxial state observed in the proportional loading test.