Copper dissolution and electrochemical behavior in EDTA- and EDA-based solutions for steam generator chemical cleaning

Abstract Pitting corrosion was the primary cause of the Alloy 600 (UNS N06600) steam generator tube degradation in a Korean pressurized water reactor (PWR) plant. Pulled tube examinations and remedial measures were carried out to mitigate the pitting. Based on the destructive examinations, the main causes of pitting corrosion were considered to be the following: accumulated sludge with a high copper content due to corrosion of copper alloys in the secondary system, acidic crevice conditions caused by chloride from condenser leakage, and ingress of air during layup. Countermeasures such as copper alloy replacement, water chemistry control, and chemical cleaning were implemented to mitigate the pitting. Chemical cleaning was evaluated as the most effective.

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Comparison of Electrochemical Behavior of Cu-10Ni-10Zn Alloy and Cu in Aqueous Solutions

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2014-0627 ◽

2015 ◽

Vol 229 (3) ◽

Cited By ~ 1

Author(s):

Waheed A. Badawy ◽

Mohamed M. El-Rabiei ◽

Hashem M. Nady ◽

Mohammed A. Samy

Keyword(s):

Electrochemical Behavior ◽

Electrochemical Impedance ◽

Electrochemical Techniques ◽

Pure Copper ◽

Open Circuit ◽

Chloride Ions ◽

Alloy Surface ◽

Metallic Surface ◽

Copper Dissolution ◽

Basic Solutions

AbstractThe electrochemical behavior of Cu-10Ni-10Zn alloy and Cu was investigated in acidic, neutral and basic solutions. The effect of chloride ions in neutral solutions was also studied. Conventional electrochemical techniques and electrochemical impedance spectroscopy were used. The corrosion rate of these materials in acidic solutions is relatively high compared to that in neutral or basic solutions. The open-circuit potential of the alloy is nearly the same as that of pure copper in the different media, indicating that the processes which occur on the alloy surface are mainly governed by copper dissolution. In chloride solutions the rate of Cu corrosion is remarkably high. In the alloy, the copper dissolution was suppressed by the presence of nickel and zinc, due to the formation of complex oxide layers. The impedance data were fitted to equivalent circuit models that explain the different electrochemical processes occurring at the electrode/electrolyte interface. SEM and EDAX have shown that the alloy surface is enriched with Ni. In neutral solutions the chloride ions are penetrating the metallic surface.

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Steam Generator Secondary Side Chemical Cleaning During Reactor Plant Cooling Down

Volume 1: Plant Operations, Maintenance, Engineering, Modifications, Life Cycle and Balance of Plant; Nuclear Fuel and Materials; Radiation Protection and Nuclear Technology Applications ◽

10.1115/icone21-16127 ◽

2013 ◽

Author(s):

Xiaojiao Xia ◽

Juhua Wen ◽

Weigang Ma

Keyword(s):

Heat Exchange ◽

Steam Generator ◽

Exchange Capacity ◽

General Corrosion ◽

Test Results ◽

Steam Generators ◽

Chemical Cleaning ◽

Safety Test ◽

Cleaning Technology ◽

Secondary Side

For safe and reliable operation of NPP steam generators, it is required to remove the sludge from heat exchanging tubes and steam generator (SG) volume in due time. Chemical cleaning technology of SG secondary side during NPP cooling down will be used in Tianwan NPP, which was used to remove iron and copper oxides from steam generators secondary side in Russia NPPs and to resume the heat exchange capacity of heat exchange tubes. To validate and evaluate the effectiveness and safety of the SG cleaning formula during NPP cooling down provided by Russia (RF) for Tianwan NPP, cleaning effective tests and safety tests were done in autoclave with the chemical cleaning process parameters simulated. To compared with RF, cleaning effective tests and safety tests were done with A3B1 under the same condition. Cleaning effective test results showed that the simulated sludge for Tianwan NPP can be more effectively dissolved and removed with A3B1 than with RF. Cleaning safety test results showed that the general corrosion amount of 0Cr18Ni10Ti stainless steel was very low but the general corrosion amount of SA508-III steel was high both with A3B1 formula and the formula provided by Russia.

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