Abstract
Effects of a variety of water chemistry conditions on the theoretical understanding and development of an electrochemical corrosion potential (ECP) prediction model to calculate the ECP of structural materials in boiling water reactors (BWR) are described. In particular, the effects of dissolved oxygen (O2), hydrogen (H2), and hydrogen peroxide (H2O2), water flow rate, and corrosion rate of Type 304 (UNS S30400) stainless steel (SS) are considered. Various electrochemical kinetic parameters used for the ECP prediction model were measured experimentally in high-temperature, high-purity water at 288°C. However, to develop the ECP model in the presence of H2O2, the electrochemical kinetic constants for the H2O2 reduction reaction were assumed to take the same values as those for the O2 reduction reaction. It has been shown that the presence of H2O2, water flow rate, and corrosion rate of Type 304 SS significantly affected the Type 304 SS ECP response to O2 and H2 in the water. Type 304 SS ECP values calculated by the prediction model appear to be in good agreement with limited laboratory and plant ECP data. However, more experimental work on electrochemical kinetic measurements in 288°C water containing H2O2 or O2 + H2O2 mixtures and in the presence of impurities is needed to improve the current ECP model.
