Abstract
Corrosive conditions in primary cooling systems of boiling water reactors (BWRs) are determined by oxidants, e.g., O_2, H_2O_2 and other corrosive radiolytic species. In this study, to determine the effect of H_2O_2 on the corrosion of the stainless steel in high temperature water, the electrochemical corrosion potential (ECP) and frequency dependent complex impedance (FDCI) of stainless steel specimens exposed to high temperature water containing H_2O_2 were measured. And the electric resistances of the oxide film in high temperature water were also measured. Obtained results are summarized in follows. 1) The ECP kept at same level at the wide range from 10ppb to 100 ppb of H_2O_2. 2) The sum of the anodic resistance and electric resistance of oxide film depended upon [H_2O_2], which was determined by the equivalent circuit analyses of measured FDCI. 3) The specific electric resistance of oxide film was about 3 MΩ cm, which was much smaller than the anodic resistance. It was confirmed that the dependency of FDCI on [H_2O_2] was mainly determined by the anodic resistance. 4) From the obtained results, the sensor complex for ECP and FDCI measurements was proposed to determine [H_2O_2] directly in high temperature water.
