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Journal Articles

Effect of seawater components on corrosion behavior of SUS316L in nitric acid solution containing metal ions

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:0 Percentile:0.01(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.

Journal Articles

Corrosion behaviour of FeCrAl-ODS steels in nitric acid solutions with several temperatures

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 60$$^{circ}$$C, 80$$^{circ}$$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.

Journal Articles

Effect of Ru chemical form on corrosion behavior of structural materials in spent fuel reprocessing process

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.

Journal Articles

Effect of chloride ion on corrosion behavior of SUS316L-grade stainless steel in nitric acid solutions containing seawater components under $$gamma$$-ray irradiation

Sano, Yuichi; Ambai, Hiromu; Takeuchi, Masayuki; Iijima, Shizuka; Uchida, Naoki

Journal of Nuclear Materials, 493, p.200 - 206, 2017/09

 Times Cited Count:5 Percentile:58.67(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$$_{3}$$ solution containing seawater components, including under the $$gamma$$-ray irradiation condition. Electrochemical and immersion tests were carried out using a mixture of HNO$$_{3}$$ and artificial seawater (ASW). In the HNO$$_{3}$$ 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$$_{2}$$ and NOCl, generated in the reaction between HNO$$_{3}$$ and Cl$$^{-}$$ ions. The corrosion rate decreased with the immersion time at low concentrations of HNO$$_{3}$$, while it increased at high concentrations. Under the $$gamma$$-ray irradiation condition, the corrosion rate decreased due to the suppression of the cathodic reactions by the reaction between the above oxidants and HNO$$_{2}$$ generated by radiolysis.

Journal Articles

Effect of sulfate ion on corrosion behavior of SUS316L in high active liquid waste

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.

Journal Articles

Effect of seawater on corrosion of SUS316L in HAW under $$gamma$$-ray irradiation

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 $$gamma$$-ray irradiation, and revealed that no significant effect of seawater components was emerged.

Journal Articles

Corrosion behavior of SUS316L in nitric acid solution containing seawater components

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$$_{3}$$ solution. Electrochemical and immersion tests were carried out using a mixture of HNO$$_{3}$$ and artificial seawater (ASW). In the HNO$$_{3}$$ 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$$_{2}$$ and NOCl, generated in the reaction between HNO$$_{3}$$ and Cl$$^{-}$$ ions. In addition, pitting corrosion occurred simultaneously at low HNO$$_{3}$$ concentrations. The corrosion rate decreased with the immersion time at low concentrations of HNO$$_{3}$$, 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$$_{3}$$. On the other hand, high-concentration HNO$$_{3}$$ 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$$_{3}$$ and ASW.

JAEA Reports

Countercurrent extraction/stripping experiments using TDdDGA solvent extractant in a centrifugal contactors system

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

JAEA-Research-2015-021.pdf:2.3MB

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.

Oral presentation

Corrosion behavior of carbon steel in irradiated chloride-containing water

Ambai, Hiromu; Sano, Yuichi; Takeuchi, Masayuki; Hoshi, Masayuki; Sakauchi, Nobuyuki; Aose, Shinichi; Ogino, Hideki

no journal, , 

no abstracts in English

Oral presentation

Corrosion resistance of tank material used for flock storage

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.

Oral presentation

Effect of seawater on corrosion of materials used in reprocessing process, 1; Corrosion of storage tank for high level liquid waste

Sano, Yuichi; Ambai, Hiromu; Takeuchi, Masayuki; Uchida, Naoki; Taguchi, Katsuya

no journal, , 

The effect of seawater on the corrosion of vessel material for HLLW storage was investigated concerning the reprocessing of spent nuclear fuels in the Fukushima Daiichi Nuclear Power Plant. Under some conditions with high seawater content, pitting corrosion and increase of corrosion rate were observed.

Oral presentation

Corrosion resistance of tank material for flock storage, 2; Corrosion behavior in fluid flow condition by air agitation

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.

Oral presentation

Development of in-situ observation and testing method for corrosion behaviors of various metals in fluid flow condition

Ambai, Hiromu; Sano, Yuichi; Kato, Toshihiro

no journal, , 

Corrosion behaviors in fluid flow condition can be different from those in static condition. Also it is noted that corrosion rates make a big change by nitric acid flow in nuclear fuel reprocessing plants. Until now, long term immersion tests in fluid flow condition which need coupons removing were conducted and thus a method which can test in a shorter time is required. In this study, we used scanning electrochemical measurement system which can measure corrosion potentials of material surfaces etc. and tried in-situ observations of effects on electrochemical properties from solution composition and flow rate in high concentration nitric acid flow condition. Furthermore, we considered a testing method to predict corrosion behaviors from same data and corrosion wastage data.

Oral presentation

Corrosion resistance of tank material for flock storage

Ambai, Hiromu; Sano, Yuichi; Takeuchi, Masayuki; Koma, Yoshikazu

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.

Oral presentation

Effect of seawater on corrosion of materials used in reprocessing process, 3; Corrosion of storage tank for high level liquid waste

Ambai, Hiromu; Nishizuka, Yusuke; Sano, Yuichi; Uchida, Naoki; Taguchi, Katsuya; Takeuchi, Masayuki

no journal, , 

As part of the investigation of reprocessing the spent nuclear fuels which are stored in the spent fuel pools of Fukushima Daiichi Nuclear Power Plant, we studied the influence of seawater components on the corrosion of storage tank for high level liquid waste. From the results of our corrosion experiments by using simulated high level liquid waste, the corrosion is inhibited by seawater components.

Oral presentation

Effect of seawater on corrosion of materials used in reprocessing process, 4; Corrosion of storage tank for high level liquid waste

Ambai, Hiromu; Nishizuka, Yusuke; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka

no journal, , 

As a part of studies about reprocessing of the spent nuclear fuels in the storage pool at the Fukushima Daiichi Nuclear Power Plant, we investigated the effect of seawater components in high activity liquid waste on the corrosion. The corrosion tests with $$gamma$$ ray irradiation showed that sea water components didn't make significant difference in the corrosion.

Oral presentation

Corrosion behavior of SUS316L in nitric acid solution containing seawater components; Effect of metal ions in high active liquid waste

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.

Oral presentation

Irradiation effect on corrosion behavior of SUS316L in nitric acid solution containing seawater components

Sano, Yuichi; Ambai, Hiromu; Nishizuka, Yusuke*; Iijima, Shizuka; Uchida, Naoki

no journal, , 

The effect of $$gamma$$-ray irradiation on the corrosion behavior of SUS316L stainless steel, which is a typical material for the equipment used in reprocessing, in HNO$$_{3}$$ solution containing seawater components was investigated. Severe corrosion just after immersion and thin streaks of corrosion, which are observed in HNO$$_{3}$$ solution containing seawater components, were prevented by $$gamma$$-ray irradiation. The generation of Cl$$_{2}$$ was decreased by $$gamma$$-ray irradiation, and it would suppress the corrosion progress.

Oral presentation

Effect of nitric acid concentration on corrosion behavior of Fe-12Cr-6Al based oxide dispersion strengthened steels

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

no journal, , 

A FeCrAl-ODS steel has been developed for the accident tolerant fuel cladding of light water reactors in Japanese projects. Spent fuel are reprocessed in Japan, namely spent fuel pins are chopped and immersed into a hot nitric acid solution to leach out the fuel. Behavior of the corrosion products from fuel cladding should be evaluated to estimate the influence of those on the reprocessing process. In this study, effect of nitric acid concentration on corrosion behavior of Fe-12Cr-6Al based oxide dispersion strengthened steels was evaluated.

Oral presentation

Effect of nitric acid concentration on corrosion behavior of 12%Cr, 6%Al oxide dispersion-strengthened steel which is a new cladding material

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

no journal, , 

As part of a study of nuclear fuel reprocessing process, the effect of nitric acid concentration on the corrosion behavior of 12%Cr, 6%Al oxide dispersion-strengthened steel which is developed as a new cladding material was evaluated. The corrosion rate was increased with increasing nitric acid concentration at boiling point. But this material had a good corrosion resistance and active corrosion didn't occur. The corrosion resistance can be attributed to Al as well as Cr. The acceleration of the corrosion rate with increasing nitric acid concentration was caused by the increase of the passive current density.

27 (Records 1-20 displayed on this page)