Optimum EDTA solvent chemistry for iron oxide removal at 150 °C

Hur, Do Haeng; Choi, Myung Sik; Chung, Han Sub; Kim, Uh Chul

doi:10.1016/s0022-3115(02)00912-1

Cited by 5 publications

(3 citation statements)

References 2 publications

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“…Based on this work, if caustic environments are formed in heated crevices covered with magnetite deposits and within porous deposits on the tubes, the deposits would be dissolved. In contrast, the deposit inventory of SGs increases during plant operation and is thus removed by sludge lancing and chemical cleaning [ 39 , 40 , 41 ]. The deposit flakes used in the dissolution test were also formed in an operating SG.…”

Section: Resultsmentioning

confidence: 99%

On the Use of NaOH Solution to Simulate the Crevice Conditions of a Nuclear Steam Generator

Hur

Song²,

Han

et al. 2022

Materials

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The corrosion behavior and integrity of steam generator (SG) tube materials have frequently been tested in solutions containing sodium hydroxide (NaOH), assuming that NaOH is a typical contaminant concentrated in the crevices of SGs in a pressurized water reactor. The purpose of this study was to investigate the adequacy of using concentrated NaOH solutions to simulate the crevice environments of SGs. The dissolution behavior of magnetite deposit flakes formed in an operating SG was tested in a 0.4 wt.% NaOH solution at 300 °C, and the thermodynamic stability of magnetite was investigated using the potential-pH diagram for an iron–water system. The magnetite deposits were rapidly dissolved in the test solution, which was supported by the fact that magnetite is thermodynamically unstable under the test condition to dissolve to dihypoferrite ions (HFeO2−). These results indicate that research data obtained from concentrated NaOH solutions are not appropriate to apply to the crevice environments of SGs.

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Section: Resultsmentioning

confidence: 99%

On the Use of NaOH Solution to Simulate the Crevice Conditions of a Nuclear Steam Generator

Hur

Song²,

Han

et al. 2022

Materials

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“…on SG tubes surface and tube support plates water passage, leading respectively to fouling and clogging of SG, which are two main sources of SG degradation and performance loss. Moreover, the precipitation of CPs in flow restricted area could lead to the sequestration of impurities with a potential impact on the stress corrosion cracking (SCC) of SG tubes [1,2]. This latter may lead to leakage [3], in this case a primary-to-secondary leakage and potential contamination of secondary circuit [4,5].…”

Section: Introductionmentioning

confidence: 99%

Mechanism and kinetics of hematite reduction under typical PWR secondary circuit condition

Chanéac

Berger

et al. 2020

Journal of Nuclear Materials

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Hydrazine is added into secondary circuit in order to eliminate oxygen and to impose a reducing potential. Another possible role of hydrazine is to reduce hematite potentially present and thus reduce risk of stress corrosion cracking of steam generator tubes. However, the latter effect of hydrazine is still not clear. In order to better understand the mechanism and the kinetics of hematite reduction by hydrazine under secondary circuit conditions (275°C, slightly alkaline, diluted hydrazine), an experimental study has been carried out. It was found that the reduction of hematite proceeds through the adsorption of hydrazine, surficial reduction and dissolution of hematite, and coprecipitation of well crystallized octahedral magnetite.

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“…It involves the removal of the contaminants using chemical agents. Organic acids have been used as the chemical agents for dissolving the ferrite in previous studies, [2][3][4][5] and several commercialized processes including AP-CITROX and LOMI have been developed. 6,7) These chemicals were acted as reducing and complexant agents.…”

Section: Introductionmentioning

confidence: 99%

Decontamination of Radioactive Contaminants from Iron Pipes using Reactive Microemulsion of Organic Acid in Supercritical Carbon Dioxide

Shimizu

Sawada

Enokida

et al. 2006

J. Nucl. Sci. Technol.

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The ferrite fixed on the iron pipes was decontaminated by a reactive microemulsion in supercritical carbon dioxide (SC-CO 2). The specimens were prepared by treating the iron pipes with steam at 1,273 K for 2 min. The specimen was not dissolved in 3 molÁdm À3 HNO 3 because its surface was covered with ferrite, while the original iron pipe was easily dissolved. This difference was used for determination of the fraction of ferrite. The fraction of ferrite covering the iron pipes was 1:5AE0:3 wt%. A microemulsion containing organic acid was prepared using a fluorinated reagent, pentadecafluorooctanoic acid (PFOA), and a non-fluorinated surfactant, polyoxyethylene (2) nonylphenyl ether (NP-2) and citric acid. In the former system, PFOA acted as a surfactant as well as an acid. By observation of the phase equilibrium, the microemulsion was found to be stabilized when the molecular ratio of water to surfactant, the w value, was 5.0 for the PFOA+H 2 O+SC-CO 2 system, and 8.7 for the NP-2+citric acid+SC-CO 2 system at 25 MPa, and 323 or 353 K. Although the removal fractions of the ferrite were 0 and 1% for the PFOA and NP-2 system, respectively, at 25 MPa, 323 K, they increased to 92 and 56% at 25 MPa, 353 K.

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Optimum EDTA solvent chemistry for iron oxide removal at 150 °C

Cited by 5 publications

References 2 publications

On the Use of NaOH Solution to Simulate the Crevice Conditions of a Nuclear Steam Generator

On the Use of NaOH Solution to Simulate the Crevice Conditions of a Nuclear Steam Generator

Mechanism and kinetics of hematite reduction under typical PWR secondary circuit condition

Decontamination of Radioactive Contaminants from Iron Pipes using Reactive Microemulsion of Organic Acid in Supercritical Carbon Dioxide

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