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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

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

Study of treatment method for damaged fuel removed from the spent fuel pool; Outline of annual report for JFY 2013 and 2014 (Contract research)

Iijima, Shizuka; Uchida, Naoki; Taguchi, Katsuya; Washiya, Tadahiro

JAEA-Review 2015-018, 39 Pages, 2015/11

JAEA-Review-2015-018.pdf:3.95MB

There is a possibility that the fuel assemblies stored in the spent fuel pool (SFP) at Fukushima Daiichi NPS (or Nuclear Power Station) are not only exposed to seawater and concrete fragments, but also damaged by fallen rubbles. We checked the reprocessing experiences of leak fuels at Tokai Reprocessing Plant and overseas reprocessing facilities, and the storage conditions and the checked and inspected results of the fuel stored in the SFP at Fukushima Daiichi NPS, after that, we listed up the technological problems with reprocessing damaged nuclear fuels and selected elements of the research for the purpose of drawing indicators to make a judgmental decision of the possibility of damaged nuclear fuels reprocessing. And we drew the indicators to make a judgmental decision on the possibility of reprocessing based on the results of the examination and the study about elements of the research.

Oral presentation

The Evaluation of a nuclear fuel material shifting to Hull

Takeyasu, Shinji; Kuroda, Yasuji; Iijima, Shizuka; Goto, Yuichi

no journal, , 

no abstracts in English

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

Clean-up activity of spent fuel powder (UO$$_{2}$$ powder) in mechanical treatment cell at Tokai Reprocessing Plant

Furuuchi, Yuta; Sato, Shinji; Yatabe, Hitoshi; Yokota, Satoru; Yamada, Takashi; Yahagi, Fumio; Terunuma, Hirotaka; Tokoro, Takeshi; Takahashi, Akihiro; Iijima, Shizuka; et al.

no journal, , 

Clean-up activity of spent fuel powder (UO$$_{2}$$ powder) in mechanical treatment cell was performed for the purpose of the preparation of decommissioning at TRP. For the clean-up activity, we selected an inexpensive vacuum cleaner and made tools, that was improved taking into account of use by means of a crane or a manipulator in the high dose cell, and applied it after a mock-up test. We report our experience and knowledge provided through this clean-up activity.

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