Cathodic polarization curves of the oxygen reduction reaction on various structural materials of boiling water reactors in high temperature–high purity water

Abstract

Cathodic polarization curves of the O 2 reduction reaction were measured by using electrodes made from typical structural materials of boiling water reactors (BWRs) to evaluate the effects of kind of material on the electrochemical corrosion potential (ECP) calculation. To estimate ECPs at any region in the BWRs on the basis of the BWR environmental conditions, anodic and cathodic polarization curves should be obtained in advance under relevant conditions. The concentration of oxidants such as O 2 and H 2 O 2 in coolant changes depending on the region in which they exist. As well, reduction reaction rates might differ depending on the kind of materials. In this work, the cathodic polarization curves of type 316L stainless steel (316L SS) and Alloy 182 were measured in high purity water at 553 K with different O 2 concentrations and compared with those of type 304 SS (304 SS). The results showed that the cathodic polarization curves differed depending on the kind of materials at the activation-controlled region. But, the difference in the ECP vs. O 2 concentration relationship was small when the ECPs were calculated by using both anodic and cathodic polarization curves measured on the objective material.

Revealing How Alkali Cations Affect the Surface Reactivity of Stainless Steel in Alkaline Aqueous Environments

“…On the other hand, identical anodic behaviors were observed between the Li- and K-containing solutions indicating similar anodic passivation processes. Note that E corr refers to the mixed potential that is dependent on both the anodic and cathodic reactions 42 and is distinct from the surface potential of the substrate determined using DLVO analysis. Although the observed differences in the Tafel polarization curves suggest that surface reactivity and consequently the kinetics of cathodic reactions are indeed influenced by the EDL, a definite conclusion regarding the effect of cations cannot be derived due to the small difference between i corr and E corr assessed in relevant solutions.…”

Water chemistry technology – one of the key technologies for safe and reliable nuclear power plant operation

“…Usually polarization curves have been measured in high conductivity water by adding electrolyte [55], but new technologies based on the adjacent reference electrode method were successfully applied to measure those under highly purified water at elevated temperature (Figure 12) [56].…”