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Hasegawa, Kenta; Goto, Ichiro*; Miyazaki, Yasunori; Ambai, Hiromu; Watanabe, So; Watanabe, Masayuki; Sano, Yuichi; Takeuchi, Masayuki
Mechanical Engineering Journal (Internet), 11(2), p.23-00407_1 - 23-00407_8, 2024/04
Hasegawa, Kenta; Goto, Ichiro*; Miyazaki, Yasunori; Ambai, Hiromu; Watanabe, So; Watanabe, Masayuki; Sano, Yuichi; Takeuchi, Masayuki
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 5 Pages, 2023/05
Ambai, Hiromu; Nishizuka, Yusuke*; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka; Shiwaku, Hideaki; Yaita, Tsuyoshi
Journal of Nuclear Science and Technology, 56(2), p.193 - 200, 2019/02
Times Cited Count:2 Percentile:18.62(Nuclear Science & Technology)During the accident that occurred at the Fukushima Daiichi Nuclear Power Plant, a large volume of seawater was introduced as coolant into the storage pools for spent nuclear fuel. If this fuel is reprocessed, some components of seawater will be mixed with the nitric acid solution containing metal ions in the reprocessing process where stainless steels are used as structural material. In this study, we investigated the effect of seawater components in high active liquid waste (HAW) containing nitric acid and metal ions as fission products on the corrosion behavior of SUS316L stainless steel. Corrosion tests were conducted in surrogate HAW containing artificial seawater (ASW). Intergranular corrosion was observed in the HAW with ASW, where Ru increased the corrosion potential to the transpassive region. An increase in the amount of ASW led to a decrease in the corrosion rate and suppression of intergranular corrosion. Interactions between Ru ions and seawater components, such as chloride ions, were indicated by the results of extended Xray absorption fine structure spectroscopy and cyclic voltammetry analyses of the solution containing ASW and HAW.
Takahatake, Yoko; Ambai, Hiromu; Sano, Yuichi; Takeuchi, Masayuki; Koizumi, Kenji; Sakamoto, Kan*; Yamashita, Shinichiro
Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 9 Pages, 2018/10
The corrosion behaviour of FeCrAl-ODS steels for the accident tolerant fuel cladding of LWRs were investigated in nitric acid solutions for the reprocessing process of spent fuels. The corrosion tests were carried out at 60C, 80
C and the boiling point of the solutions, and the specimens were then analysed by XPS. The corrosion remarkably progressed at the boiling point, and the highest corrosion rate was 0.22 mm/y. In the oxide film, the atomic concentration of Fe was lower, than that in the base material, and those of Cr and Al were higher. The results show that the corrosion of FeCrAl-ODS steels in hot nitric acid solution is not severe because of the high corrosion resistance of the oxide film formed on the material; hence, the corrosion resistance of the new cladding materials in the dissolution process of spent fuel is acceptable for reprocessing operations.
Sano, Yuichi; Ambai, Hiromu; Takahatake, Yoko
Aichi Shinkurotoron Hikari Senta 2017-Nendo Kokyoto Riyo Seika Hokokusho (Internet), 1 Pages, 2018/00
In order to elucidate the mechanism of corrosion in the reprocessing process and propose a method for suppressing corrosion, the effect of coexisting substances on the chemical form of Ru in nitric acid solution containing seawater components was evaluated. The result of XAFS measurement for Ru showed the structural change around a Ru atom due to the interaction with chloride ion, which will suppress the corrosion promoting action of Ru in nitric acid solution.
Sano, Yuichi; Ambai, Hiromu; Takeuchi, Masayuki; Iijima, Shizuka; Uchida, Naoki
Journal of Nuclear Materials, 493, p.200 - 206, 2017/09
Times Cited Count:9 Percentile:61.86(Materials Science, Multidisciplinary)Concerning the Fukushima Daiichi Nuclear Power Plant accident, we investigated the effect of chloride ion on the corrosion behavior of SUS316L stainless steel, which is a typical material for the equipment used in reprocessing, in HNO solution containing seawater components, including under the
-ray irradiation condition. Electrochemical and immersion tests were carried out using a mixture of HNO
and artificial seawater (ASW). In the HNO
solution containing high amounts of ASW, the cathodic current densities increased and uniform corrosion progressed. This might be caused by strong oxidants, such as Cl
and NOCl, generated in the reaction between HNO
and Cl
ions. The corrosion rate decreased with the immersion time at low concentrations of HNO
, while it increased at high concentrations. Under the
-ray irradiation condition, the corrosion rate decreased due to the suppression of the cathodic reactions by the reaction between the above oxidants and HNO
generated by radiolysis.
Ambai, Hiromu; Sano, Yuichi; Nishizuka, Yusuke*; Iijima, Shizuka; Uchida, Naoki
Zairyo To Kankyo, 66(5), p.169 - 172, 2017/05
We study the effect of sulfate ion which is one component of seawater or concrete on the corrosion behavior in high active liquid waste tank environment. The corrosion tests were conducted using SUS316L and surrogate high active liquid waste containing some metal ions and nitric acid. The results showed that sulfate ion inhibited the corrosion rates. The XPS results indicated the attachment of sulfate ion to material surfaces suppressed the anode reaction.
Ambai, Hiromu; Nishizuka, Yusuke*; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka
QST-M-2; QST Takasaki Annual Report 2015, P. 90, 2017/03
The spent fuel stored in the storage pools at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company Holdings, Inc. is exposed with the environment containing seawater components, owing to the injection of seawater into the storage pools. Therefore, during reprocessing, it is expected that the spent fuel will be contaminated with seawater components, and the influence of seawater on reprocessing needs to be investigated. We conducted the corrosion tests of the HAW storage tanks under -ray irradiation, and revealed that no significant effect of seawater components was emerged.
Sano, Yuichi; Ambai, Hiromu; Takeuchi, Masayuki; Iijima, Shizuka; Uchida, Naoki
Proceedings of European Corrosion Congress 2016 (EUROCORR 2016) (USB Flash Drive), 10 Pages, 2016/09
During the Fukushima Daiichi Nuclear Power Plant accident, significant volume of seawater was injected into the storage pool for spent nuclear fuel as the coolant. In this study, we investigated the effect of seawater components on the corrosion behavior of SUS316L stainless steel in HNO solution. Electrochemical and immersion tests were carried out using a mixture of HNO
and artificial seawater (ASW). In the HNO
solution containing high amounts of ASW, the cathodic current densities increased and uniform corrosion progressed. This might be caused by strong oxidants, such as Cl
and NOCl, generated in the reaction between HNO
and Cl
ions. In addition, pitting corrosion occurred simultaneously at low HNO
concentrations. The corrosion rate decreased with the immersion time at low concentrations of HNO
, while it increased at high concentrations. It is assumed that the cathodic reactions proceed slowly and the anodic reactions are gradually prevented by the growth of an oxide film on the surface of the coupon in low-concentration HNO
. On the other hand, high-concentration HNO
triggers a vigorous cathodic reaction, which disturbs the growth of the oxide film and activates the anodic reactions. This competition between the cathodic and anodic reactions causes a change in the corrosion rates with the immersion time in a mixture of HNO
and ASW.
Kibe, Satoshi; Fujisaku, Kazuhiko*; Ambai, Hiromu; Sakamoto, Atsushi; Sano, Yuichi; Takeuchi, Masayuki; Suzuki, Hideya; Tsubata, Yasuhiro; Matsumura, Tatsuro
JAEA-Research 2015-021, 40 Pages, 2016/02
The flowsheet with TDdDGA extractant has been being developed for recovering MA from PUREX raffinate. In the previous study, the yields of MA and other elements in countercurrent extraction/stripping experiments using mixer-settlers were not enough for the target and it would be due to the insufficient phase (aqueous/organic) separation. In this study, we carried out countercurrent experiments with surrogate PUREX raffinate using centrifugal contactors which had superior phase separation ability, and evaluated the extraction/stripping behavior of each element. During the operation, abnormal fluid behavior, such as overflow and entrainment, was not observed, and sufficient phase separation was achieved by centrifugal contactors. Extraction behavior of lanthanides was similar to that in mixer-settlers, but their stripping efficiencies decreased. This would be due to shorter residence time in mixing zone.
佐野 雄一; 渡部 創; 宮崎 康典; 安倍 弘; 長谷川 健太
後藤 一郎*
【課題】粒子径が従来よりも大きく、粒子径の均一性が比較的高い粒子を製造することができる粒子製造方法を提供する。 【解決手段】本発明に係る粒子製造方法は、組成物を、振動するノズルから、撹拌機により撹拌された溶媒中に滴下し、組成物が含まれる粒子を造粒する造粒工程(ステップS1)と、前記造粒工程(ステップS1)で得られた溶媒を含む粒子から、溶媒を除去し、粒子を得る溶媒除去工程(ステップS2)と、を含むことを特徴とする。
Ambai, Hiromu; Sano, Yuichi; Takeuchi, Masayuki; Sakauchi, Nobuyuki; Hoshi, Masayuki; Ogino, Hideki; Aose, Shinichi
no journal, ,
As a part of studies on corrosion resistance of storage tanks for flock generated in the coagulation process for radioactive contaminated water from the Fukushima Daiichi Nuclear Power Plant, several corrosion tests considering the radiation and the contact with flock were carried out with SS400 in the settling condition. Average corrosion rates of SS400 were around 0.1mm/y and severe corrosion including local corrosion was not observed.
Ambai, Hiromu; Sano, Yuichi; Takeuchi, Masayuki; Sakauchi, Nobuyuki; Hoshi, Masayuki; Ogino, Hideki; Koizumi, Kenji
no journal, ,
We studied the corrosion behavior of the tank material SS400 for flock storage in fluid flow condition by air agitation. Fluid flow increased the corrosion rate and this effect was reduced by the presence of the flock. Decreasing of flow rate and change of air to inactive gas are effective in corrosion prevention measures.
Ambai, Hiromu; Nishizuka, Yusuke*; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka
no journal, ,
During the Fukushima Daiichi Nuclear Power Plant accident, a large volume of seawater was injected as coolant into the storage pool for spent nuclear fuel. If this fuel is reprocessed, some components of seawater will be mixed with the nitric acid used during spent fuel reprocessing. In this study, we investigated the effect of seawater components in high activity liquid waste (HAW) on the corrosion behavior of SUS316L stainless steel. The immersion and electrochemical tests were conducted using a solution containing artificial seawater (ASW) and surrogate HAW. In the nitric acid solution containing only ASW (without any metal ions in the HAW), pitting and / or uniform corrosion were observed. Intergranular corrosion was observed in the solution containing ASW and HAW with added metal ions, wherein Ru increased the corrosion potential to the transpassive region. An increase in amount of ASW led to decreased corrosion rates and the suppression of intergranular corrosion.
Ambai, Hiromu
no journal, ,
The fuel debris which generated in the severe accident of Fukushima Daiichi Nuclear Power Plant (1F) of the Tokyo Electric Power Company Holdings, Inc. are under the water. Thus, it is important to understand the elution behavior of nuclear species in water. It has been reported that fuel debris consist of a number of phase by studies for TMI-2 and 1F accident. We can get only averaged information about all phases using normal methods. It is expected to have a better understanding about the elution mechanism of debris. In this study, we tried the evaluation of the elution reaction on fuel debris by getting the electrochemical properties of each phase, using scanning electrochemical microscopy which can measure local electrochemical property.
Ambai, Hiromu; Goto, Ichiro*; Miyazaki, Yasunori; Sano, Yuichi; Takeuchi, Masayuki; Watanabe, Masayuki; Nemoto, Gentaro*
no journal, ,
no abstracts in English
Kuzure, Yoshiaki*; Miyagawa, Akihisa*; Nagatomo, Shigenori*; Nakatani, Kiyoharu*; Yoshida, Masaaki*; Nemoto, Shuhei*; Arai, Tsuyoshi*; Ambai, Hiromu; Hasegawa, Kenta; Sano, Yuichi
no journal, ,
Concentration dependencies of nitric acid, nitrate ion, and so on for the adsorption and elution rates (mass transfer coefficients) of FP (Ln) in silica adsorbent, carrying various NTAamide extractants, were measured in the single silica particle/solution system by fluorescence microspectroscopy. The adsorption and elution rates were improved by changing polymercoating conditions for the silica adsorbent granulated by the freeze-drying method. We will discuss the mass transfer coefficients influenced by the nitric acid and nitrate ionconcentrations.
Hasegawa, Kenta; Miyazaki, Yasunori; Ambai, Hiromu; Sano, Yuichi; Okamura, Nobuo; Watanabe, Masayuki
no journal, ,
no abstracts in English
Hasegawa, Kenta; Ambai, Hiromu; Watanabe, So; Okamura, Nobuo; Watanabe, Masayuki; Sano, Yuichi; Takeuchi, Masayuki
no journal, ,
Separation of minor actinides (MA; Am, Cm) is one of the important issues to reduce the volume of radioactive waste. Previous researches have promoted development of separation flows, safety assessment and engineering scale equipment, while long-term equipment durability for radiation and nitric acid is required for putting MA separation system into practical use. We focused on diaphragm composed of rubber materials on feed pump in contact with high-level radioactive liquid waste (HLLW). In this study, we report radiation impact assessment on mechanical property of diaphragm candidate materials which were degraded by gamma-ray irradiation in acidic or stress loading condition.
Hayashi, Naoki*; Miyagawa, Akihisa*; Nagatomo, Shigenori*; Nakatani, Kiyoharu*; Sato, Kiyomori*; Arai, Tsuyoshi*; Ambai, Hiromu; Hasegawa, Kenta; Watanabe, So; Sano, Yuichi
no journal, ,
The fluorescence of lanthanide ions within a single extractant-impregnated silica particle was obtained using a microspectrometer to evaluate their distribution behavior within the particle.