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Crevice Crrosion of Copper as an Engineering Barrier of High-level Radioactive Waste Containers

This work is aimed at determining the viability of oxygen-free copper as an engineering barrier of high-level radioactive waste containers.

Product Number: 51317--9162-SG
ISBN: 9162 2017 CP
Author: Maite Ochoa
Publication Date: 2017
Industry: Energy Generation
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This work is aimed at determining the viability of oxygen-free copper as an engineering barrier of high-level radioactive waste containers. This material stands out because of its excellent resistance to generalized and localized corrosion in aqueous electrolytes; particularly in reducing environments as the ones expected in repository sites located below the water table.As the first part of a more general analysis the corrosive effects of chloride sulfate and bicarbonate and that of temperature were studied analyzing each anion separately as well as in different combinations of them. These anions are generally present in groundwaters such as those potentially in contact with the engineered barriers of a nuclear repository. The concentrations of chloride sulfate and bicarbonate were between 0.001 and 1 M and the temperatures were between 30 and 90°C. An electrochemical characterization was carried out through the measurement of the corrosion potential and the anodic polarization curves and 8 systems were selected from the original 27 studied systems for studying stress corrosion cracking and crevice corrosion.In this stage of the work tests were developed to determine the existence of crevice corrosion: open circuit potential tests and Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) tests. Artificial crevice formers were used in both cases. Scanning electron microscopy and optical microscopy were used to characterize the creviced specimens after testing. Corrosion products composition was determined by Energy Dispersive Microanalysis (EDS).The crevice corrosion tests showed that crevice corrosion is observed only in some of the 8 selected solutions. The corrosion was not very deep and it occurred below the edges of the crevice formers. Some corrosion was observed out of the crevices indicating the possible occurrence of inverse crevice corrosion which needs further investigation.

Key words: copper, crevice corrosion, radioactive waste container, chloride, sulfate, bicarbonate

 

This work is aimed at determining the viability of oxygen-free copper as an engineering barrier of high-level radioactive waste containers. This material stands out because of its excellent resistance to generalized and localized corrosion in aqueous electrolytes; particularly in reducing environments as the ones expected in repository sites located below the water table.As the first part of a more general analysis the corrosive effects of chloride sulfate and bicarbonate and that of temperature were studied analyzing each anion separately as well as in different combinations of them. These anions are generally present in groundwaters such as those potentially in contact with the engineered barriers of a nuclear repository. The concentrations of chloride sulfate and bicarbonate were between 0.001 and 1 M and the temperatures were between 30 and 90°C. An electrochemical characterization was carried out through the measurement of the corrosion potential and the anodic polarization curves and 8 systems were selected from the original 27 studied systems for studying stress corrosion cracking and crevice corrosion.In this stage of the work tests were developed to determine the existence of crevice corrosion: open circuit potential tests and Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) tests. Artificial crevice formers were used in both cases. Scanning electron microscopy and optical microscopy were used to characterize the creviced specimens after testing. Corrosion products composition was determined by Energy Dispersive Microanalysis (EDS).The crevice corrosion tests showed that crevice corrosion is observed only in some of the 8 selected solutions. The corrosion was not very deep and it occurred below the edges of the crevice formers. Some corrosion was observed out of the crevices indicating the possible occurrence of inverse crevice corrosion which needs further investigation.

Key words: copper, crevice corrosion, radioactive waste container, chloride, sulfate, bicarbonate

 

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