Water chemistry, solution resistivity, and oxygen reduction reaction in simulated primary coolant of pressurized water reactors

Abstract

The effect of temperature (25°C-300°C) on the ohmic potential drop (ΔE Ω ) and resistivity (R sol ) of a simulated primary coolant of the pressurized water reactors was investigated using electrochemical impedance spectroscopy (EIS) and galvanostatic potentiometry. The variations in the conductivity and pH of the solution showed that by increasing the temperature the magnitude of the R sol and therefore ΔE Ω of the system first decreases rapidly (until~150°C) and then reaches a relatively stable plateau value. Increasing the pressure of the system decreased the magnitude of the R sol in the oxygenated coolant. Investigation of the oxygen reduction reaction (ORR) on platinum (Pt), 316L stainless steel (SS), Alloy 690, and carbon steel revealed the great effect of water chemistry, in particular pH on the rate of the ORR on these materials. OH − adsorption on Pt reduced the rate of the ORR on this metal at temperatures higher than~100°C. Finally, it was found that higher H 3 O + concentrations reduce the rate of the ORR on iron-and nickel-based alloys, while increasing the OH − concentration at temperatures higher thañ 150°C accelerates the rate of the ORR on these alloys. K E Y W O R D Shigh-temperature water, iR compensation, primary coolant, solution resistivity