Abstract
A common index of corrosive conditions in boiling water reactors (BWRs) is the electrochemical corrosion potential (ECP), which is determined by a combination of factors such as specimen surface conditions and oxidant concentrations (e.g. O2, H2O2 and other corrosive radiolytic species). ECP sensors can be applied to determine corrosive conditions directly at elevated temperature, but a disadvantages of this approach is the broad plateau observed in the range 10–100 ppb H2O2. To determine the concentration [H2O2] directly in high temperature water, an array consisting of an ECP sensor and a complex impedance sensor has been developed. From the results, it is concluded: (1) the radii of the low frequency semicircle of the frequency dependent complex impedance (FDCI) data (Cole–Cole plots) decreased with increasing [H2O2]. The radii for the specimen exposed to 100 ppb H2O2 were determined by the electric resistance of the oxide film, and had reached the saturation level caused by saturation of oxide film growth; (2) the performance of the sensor array has been validated by [H2O2] measurements in the high temperature, high pressure hydrogen peroxide water loop; (3) a combination of ECP and FDCI sensors is a candidate to determine [H2O2] in BWR primary coolant at elevated temperature.