• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.301-302
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• 2018

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2017.05a
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• pp.344-345
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• 2017

• Journal of the Korean institute of surface engineering
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• v.50 no.4
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• pp.251-258
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• 2017

This study was carried out with solution temperature variables of $75^{\circ}C$ and $90^{\circ}C$ for STS 304, which is a nuclear equipment material, in order to determine the corrosion damage behavior in chemical decontamination process using permanganic acid and oxalic acid. Then electrochemical polarization experiment, weight loss measurement, surface morphology observation and surface damage depth were measured every cycle of the decontamination process to analyze the degree of corrosion damage. As a result, the corrosion current density, weight loss, and surface damage increased as the decontamination process cycle increased, and the corrosion damage of STS 304 tended to increase. Few ${\mu}m$ pitting damage was observed on the surface observation. In 5 cycle, the elongated wormhole-type pitting damage appeared, leading to relatively large surface damage. However, there was no significant difference in the degree of surface damage resulting from the increase in the temperature of the chemical decontamination solution.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.291-292
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• 2018

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.15-28
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• 2019

In accordance with the decommissioning plan for the Kori Unit 1 NPP, the reactor coolant system will be chemically decontaminated as soon as possible after permanent shutdown. This study developed the chemical decontamination process though the development project of decontamination technology of reactor coolant system and dismantled equipment for NPP decommissioning, which has been carried out since 2014. In this study, Oxidation/reduction process was conducted using system decontamination process development equipment of lab scale and was divided into unit and continuous processes. The optimal process time was derived from the unit process, and decontamination agent and the number of process were derived through the continuous processes. Through the unit process, the oxidation process took 5 hours and the reduction process took 4 hours. As optimum decontamination agent, the oxidizing agent was $200mg{\cdot}L^{-1}$ Permanganic acid + $200mg{\cdot}L^{-1}$ Nitric acid and the reducing agent was $2000mg{\cdot}L^{-1}$ Oxalic acid. In the case of the number of processes, all oxide films were removed during the two-cycle chemical decontamination process of STS304 and SA508. In the case of Alloy600, all oxide films were removed when chemical decontamination was performed for three cycles or more.

• Korean Journal of Materials Research
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• v.23 no.10
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• pp.592-598
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• 2013

Graphene oxide powders prepared by two different drying processes, freeze drying and spray drying, were studied to compare the effect of the drying method on the physical properties of graphene oxide powder. The graphene oxide dispersion was prepared from graphite by chemical delamination with the aid of sulfuric acid and permanganic acid, and the dispersion was further washed and re-dispersed in a mixed solvent of water and isopropyl alcohol. A freeze drying method can feasibly minimize damage to the sample, but it requires a long process time. In contrast, spray drying is able to remove a solvent in a relatively short time, though this process requires exposure to a high temperature for a rapid evaporation of the solvent. The powders prepared by freeze drying and spray drying were characterized and compared by Raman spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and by an elemental analysis. The graphene oxide powders showed similar chemical compositions; however, the morphologies of the powders differed in that the graphene oxide prepared by spray drying had a winkled morphology and a higher apparent density compared to the powder prepared by freeze drying. The graphene oxide powders were reduced at $900^{\circ}C$ in an atmosphere of $N_2$. The effect of the drying process on the properties of the reduced graphene oxide was examined by SEM, TEM and Raman spectroscopy.