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Sakairi, Masatoshi*; Onozawa, Kento*; Otani, Kyohei; Ueno, Fumiyoshi
no journal, ,
no abstracts in English
Suzuki, Hiroyuki*; Kitayama, Ayami; Mitsui, Seiichiro; Taniguchi, Naoki
no journal, ,
The environmental conditions around carbon steel overpacks in geological disposal are expected to be diverse cases depending on geological environment of the repository and may also vary depending on changes in conditions after repository closure. In this study, with the aim of understanding corrosion behavior under such environmental conditions, immersion tests with different conditions were conducted in bentonite/silica sando mixture assuming a buffer material to be constructed around the overpack under a wide range of conditions, including temperature and water quality beyond the assumed range of conventional environmental conditions, and the effects on corrosion behavior were evaluated.
Taniguchi, Naoki; Kitayama, Ayami; Kawasaki, Manabu*; Nakayama, Masashi; Ono, Hirokazu; Mitsui, Seiichiro; Suzuki, Hiroyuki*
no journal, ,
no abstracts in English
Watari, Shingo*; Kitayama, Ayami; Mitsui, Seiichiro; Taniguchi, Naoki; Kimura, Wataru*; Kajiyama, Hiroshi*
no journal, ,
The application of pure copper is being considered for the purpose of extending the life-time of disposal canisters in the direct disposal of spent fuel. Pure copper generally shows little corrosion development in aqueous solution environments with low oxygen concentrations due to its thermodynamic stability, but pure copper loses thermodynamic stability and corrosion develops depending on the sulfides conditions. In this study, immersion tests and U-bend tests were conducted to understand the corrosion progress behavior and stress corrosion cracking behavior of pure copper under the condition of sparging gas with various hydrogen sulfide concentrations to simulate the disposal environment where sulfide exists.
Mitsui, Seiichiro; Kawakita, Ryohei; Ishidera, Takamitsu
no journal, ,
Evaluation of geological disposal deals with long-term time scales of hundreds to tens of thousands of years. On the other hand, our experiments are limited to about 20 years at the longest, and it is possible that the long-term phenomena assumed in geological disposal have not been sufficiently simulated. Regarding the corrosion behavior of carbon steel overpacks, the corrosion depths over time in immersion tests for several to ten years can be approximated by a power law. From the fact that a protective corrosion product film, such as siderite, was observed on the surface of the test piece, it is believed that this can be explained by the passive effect of the corrosion product film on the corrosion reaction. However, the effect cannot be applied to the long-term corrosion behavior based solely on the results of immersion tests. Through natural analogue studies, we concluded that the passive effect of the corrosion product film can explain long-term corrosion behavior exceeding hundreds of years.
Sato, Tomonori; Hata, Kuniki; Igarashi, Takahiro; Otani, Kyohei; Kato, Chiaki
no journal, ,
It is estimated that the outer surface of the overpack of high-level radioactive waste during the transition period of the geological disposal is exposed to the groundwater percolated into the bentonite under irradiation. So, evaluations of water radiolysis considering the contribution of bentonite is one of the important factors to understand the corrosive environment. In this study, the results of the contribution of impurities leaching from bentonite and coexistence of bentonite in the water radiolysis are reported.
Otani, Kyohei; Igarashi, Takahiro; Ueno, Fumiyoshi
no journal, ,
The effects of flowing liquid film thickness and flow rate on the corrosion behavior of metallic materials under flowing liquid film were clarified by using a novel corrosion equipment.
Miyoshi, Yuma*; Inoue, Hiroyuki*; Mitsui, Seiichiro; Dobashi, Ryuta*
no journal, ,
In Japan, research and studies on direct disposal of spent fuel as an alternative disposal option are underway in order to secure a wide range of options. For direct disposal, a copper-carbon steel composite vessel covered with pure copper, which is expected to provide longer confinement, has been considered in consideration of the time required for sufficient attenuation of C-14, one of the dominant radionuclides in the safety assessment. In this study, the effect of HCO
on the cathodic reaction of pure copper in a fresh groundwater environment with a low oxygen atmosphere was investigated. From the results of polarization measurements using pure copper as a test electrode, it was inferred that HCO promotes the cathodic reaction, which is a hydrogen evolution reaction using H
as an oxidant, by buffering the pH change at the electrode interface in the relatively low current density range, which is assumed to be the cathodic current of corrosion. It is unlikely that HCO acts directly as an oxidant in the cathodic reaction of corrosion. The hydrogen evolution reaction rate on the pure copper surface is relatively low in comparison with the polarization measurements on pure iron and platinum.
Hata, Kuniki; Sato, Tomonori; Kato, Chiaki; Sato, Nobuaki*
no journal, ,
no abstracts in English
Aoyama, Takahito; Sato, Tomonori; Ueno, Fumiyoshi; Kato, Chiaki; Sano, Naruto; Yamashita, Naoki; Igarashi, Takahiro
no journal, ,
no abstracts in English
Wakai, Satoshi*; Hirano, Shinichi*; Ueno, Fumiyoshi; Okamoto, Akihiro*
no journal, ,
no abstracts in English