In-situ monitoring of the corrosion behavior and impurity enrichment of steam generator tube materials under PWR secondary side thermal hydraulic and heat transfer conditions

摘要

A high temperature recirculation loop was developedto simulate secondary side boiling conditions in nuclearpower plant steam generators under both normal operat-ing conditions and during impurity, e.g. chloride, tran-sients. In-situ electrochemical impedance spectroscopywas used to study the corrosion behavior and impurityenrichment of steam generator tubing materials as afunction of boiling, ffiow rate and impurity levels. The ef-fect of boiling can be clearly observed in the electrochemi-cal response and in the shape of the pressure-temperaturediffierence curve. Experimental results reveal that boil-ing contributes to both the surface area of the samplein contact with the solution and increases the corrosionrate. In addition, chloride injections resulted in a fur-ther increase in the corrosion rate and, when boilingis stopped, hideout return can be observed and quanti-ed, thus enabling for the correlation between surface-chloride concentration and corrosion rate to be deter-mined. Post-test material and oxide scale characteri-zations were performed using scanning electron micro-scope, energy-dispersive X-ray spectroscopy and glow-discharge optical emission spectroscopy after exposure tosecondary side thermal hydraulic and heat transfer con-ditions, along with simulated impurity transients.