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Journal Articles

Corrosion behavior of ODS steels with several chromium contents in hot nitric acid solutions

Tanno, Takashi; Takeuchi, Masayuki; Otsuka, Satoshi; Kaito, Takeji

Journal of Nuclear Materials, 494, p.219 - 226, 2017/10

BB2016-1307.pdf:0.6MB

 Times Cited Count:9 Percentile:13.35(Materials Science, Multidisciplinary)

Oxide dispersion strengthened (ODS) steel cladding tubes have been developed for fast reactors. 9 chromium ODS and 11Cr-ODS tempered martensitic steels are prioritized for the candidate material in research being carried out at JAEA. In this work, fundamental immersion tests and electro-chemical tests of 9 to 12Cr-ODS steels were systematically conducted in various nitric acid solutions at 95$$^{circ}$$C. The corrosion rate exponentially decreased with effective solute chromium concentration (Cr$$_{eff}$$) and nitric acid concentration. Addition of oxidizing ions also suppressed the corrosion rate. According to polarization curves and surface observations in this work, the combination of low Cr$$_{eff}$$ and dilute nitric acid could not prevent the active dissolution at the beginning of immersion, and the corrosion rate was high. In comparison, higher Cr$$_{eff}$$, concentrated nitric acid and addition of oxidizing ions helped to prevent the active dissolution, and suppressed the corrosion rate.

Journal Articles

Strength anisotropy of rolled 11Cr-ODS steel

Tanno, Takashi; Yano, Yasuhide; Oka, Hiroshi; Otsuka, Satoshi; Uwaba, Tomoyuki; Kaito, Takeji

Nuclear Materials and Energy (Internet), 9, p.353 - 359, 2016/12

BB2015-1727.pdf:6.74MB

 Times Cited Count:4 Percentile:47.23(Nuclear Science & Technology)

Materials for core components of fusion reactors and fast reactors, such as blankets and fuel cladding tubes, must be excellent in high temperature strength and irradiation resistance because they will be exposed to high heat flux and heavy neutron irradiation. Oxide dispersion strengthened (ODS) steels have been developing as the candidate material. Japan Atomic Energy Agency (JAEA) have been developing 9 and 11 Chromium (Cr) ODS steels for advanced fast reactor cladding tubes. The JAEA 11Cr-ODS steels were rolled in order to evaluate their anisotropy. Tensile tests and creep tests of them were carried out at 700 $$^{circ}$$C in longitudinal and transverse orientation. The anisotropy of tensile strength was negligible, though that of creep strength was distinct. The observation results and chemical composition analysis suggested that the cause of the anisotropy in creep strength was prior powder boundary including Ti-rich precipitates.

Oral presentation

Effect of thermo-mechanical treatment on nano-structure of 9Cr-ODS steel

Oka, Hiroshi; Tanno, Takashi; Otsuka, Satoshi; Yano, Yasuhide; Kaito, Takeji; Onuma, Masato*

no journal, , 

Microstructural changes of 9Cr-ODS steel introduced by thermo-mechanical treatment (hot isostatic press (HIP), hot extrusion, and hot forge) were evaluated. The weight-ratio of residual ferrite phase reduced and the number density of nano-oxide particle decreased after the thermo-mechanical treatment. The change of number density and size of nano-oxide particle would affect the weight-ratio of residual ferrite phase because the formation of the residual ferrite phase is led by the pin effect of the nano-oxide particle.

Oral presentation

Transient burst properties of ODS steel cladding for evaluating sever accident

Inoue, Toshihiko; Sekio, Yoshihiro; Otsuka, Satoshi; Yano, Yasuhide; Tanno, Takashi; Oka, Hiroshi; Furukawa, Tomohiro; Kaito, Takeji; Torimaru, Tadahiko*; Hayashi, Shigenari*; et al.

no journal, , 

In order to evaluate the strength and deformation in severe accident, the transient burst tests were carried out with various heating rates (from 0.1 to 10 K/s) and hoop stresses (from 50 to 200 MPa) to provide more evaluation data. The test materials were core materials in fast reactors, 9-18Cr-ODS and accident tolerant fuel cladding tube in the light water reactors, FeCrAl-added ODS ferritic steels. Result, the rupture strength dropped with increasing hoop stress and decreasing heating rate. The burst strength of Al-added ODS steels was lower than other ODS steels, Al and Zr-added ODS steels show good transient burst strength.

Oral presentation

Development of technologies for reduction in volume and toxicity of high-level radioactive wastes, 2; Challenges in fast reactor cycle

Maeda, Seiichiro

no journal, , 

The uranium-plutonium mixed oxide (MOX) fuel bearing several percent minor actinides is adopted as the fast reactor fuel to reduce the high level radioactive waste volume and its toxicities. Their physical properties such as melting points and thermal conductivities are investigated symmetrically. It is getting clear that the effect of MA bearing is not so significant. The MOX fuel pins including up to 5% of Am were irradiated in Joyo to confirm their irradiation performance. Some types of irradiation experiments using MA-MOX fuels are planned after Joyo restart. The obtained data will contribute to develop fuel pin performance codes for MA-MOX fuels. SmART (Small Amount of Reuse Fuel Test) cycle program is in progress to demonstrate MA recycles starting from FR spent fuels. Furthermore, long life cladding with ODS steel is under development to enhance the transmutation efficiency of MA in one cycle. Thus, R&Ds in FR systems advances steadily to solve the waste issue.

Oral presentation

Welding technology development of accident tolerant ODS steel fuel cladding, 2

Yuzawa, Sho*; Yabuuchi, Kiyohiro*; Kimura, Akihiko*; Sakamoto, Kan*; Hirai, Mutsumi*; Yamashita, Shinichiro

no journal, , 

Oxide dispersion strengthened steel with high Cr and Al concentration in chemical composition (FeCrAl-ODS steel) has been proposed as a promising candidate for the accident tolerant fuel cladding of light water reactors (LWRs) because of their excellent oxidation and corrosion resistance under high temperature water and steam environments. Neither there are no sufficient knowledge on welding technology of FeCrAl-ODS nor it is known that aluminum addition remarkably degrades the weldability of the ODS steel. In this study, electron beam (EB) welding and tungsten inert gas (TIG) welding were applied to the SUS430 endcap welding to cladding tube made of FeCrAl-ODS steel and performed the bonding strength and corresponding damage structure evaluations at the bonding part.

Oral presentation

Analysis of nanostructures in ODS steels

Suzuki, Akihiro*; Onuma, Masato*; Tanno, Takashi; Oka, Hiroshi

no journal, , 

no abstracts in English

Oral presentation

R&D of advanced stainless steels for BWR fuel claddings, 4-5; Investigation of corrosion behavior in nitric acid solution for reprocessing process

Takahatake, Yoko; Ambai, Hiromu; Sano, Yuichi; Takeuchi, Masayuki; Watanabe, Masayuki; Sakamoto, Kan*; Yamashita, Shinichiro

no journal, , 

no abstracts in English

Oral presentation

Stability of nano-particles in ODS steel cladding for fast reactor irradiated to about 240 dpa

Oka, Hiroshi; Tanno, Takashi; Yano, Yasuhide; Tachi, Yoshiaki; Otsuka, Satoshi; Kaito, Takeji

no journal, , 

9Cr-ODS steel was irradiated to approximately 240 dpa at 700 $$^{circ}$$C by using an ion irradiation where the irradiation condition is close to that of a commercial fast reactor cladding tube. Microstructural observation was performed on the nano-sized particles, which is the main factors of the excellent high-temperature strength of 9Cr-ODS steel. The observation revealed that the nano-sized articles of about 5 nm were uniformly dispersed with high density even after irradiation up to 240 dpa. Furthermore, no void formation was observed. Thus, it was concluded that the nano-sized articles of 9Cr-ODS steel exist stably under a high-dose irradiation condition at a practical level at 700 $$^{circ}$$C.

Oral presentation

Evaluation of nano-sized oxide dispersion condition in ODS steel by atom probe tomography

Tanno, Takashi; Yano, Yasuhide; Oka, Hiroshi*

no journal, , 

3-dimensional atom prove tomography (3D-APT) was applied to JAEA 9Cr-ODS steel as trial, and the dispersion condition of nano-sized oxide was evaluated. 3D-APT was successfully carried out and the dispersion condition in tiny tip was obtained. 3D-APT mapping showed that the nano-sized oxide is Y-Ti-O complexed, and there could be chemical distribution.

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