Corrosion of alloy 690 in simulated steam generator chemistry with boiling-effect of chloride and sulfate impurities

• DOI: 10.1016/j.electacta.2023.142129
• Publication Date: 2023-02-27T21:00:15Z
• Authors: Konsta Sipilä; Tiina Ikäläinen; Tiina Lavonen; Timo Saario; Caitlin Huotilainen; Iva Betova; Martin Bojinov
• Keywords: Nickel-base alloy; Impurity deposition/release; 0202 electrical engineering, electronic engineering, information engineering; Secondary coolant; 02 engineering and technology; Corrosion mechanism; ta215; Sub-nucleate boiling

Enrichment of impurities occurs in steam generators of nuclear plants due to intense boiling conditions prevailing within them. In this work, deposition and release of chloride and sulfate impurities were studied using a dedicated water circulation loop with Alloy 690 as steam generator tubing. Electrochemical impedance spectroscopy was employed to follow in-situ the corrosion behavior in non-boiling, boiling and after-boiling conditions. Deposition/release of impurities is quasi-first-order vs. concentration. Interpretation of electrochemical impedance data using an updated version of the Mixed-Conduction Model allows to obtain reaction orders of oxide growth and corrosion release with respect to chloride and sulfate additives.