Earlier work evoked a cathodic depolarization model of ferrous me tais based on the removal from the surface of atomic hydrogen by S RBs (5) and/or hydrogen consumption thanks to a hydroge nase enzyme (6-9). This hypothesis was investigated and can be

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Zajec (2020): Stress corrosion crack initiation testing with tapered specimens in high-temperature waterresults of a collaborative research project, Corrosion Engineering, Science and Technology,

The initiation of stress corrosion cracks in sensitised austenitic stainless steel under high temperature water conditions (simulated boiling water reactor environment) was detected, applying electrochemical noise measurement technique. The stress corrosion cracks were generated on pre‐oxidised, unnotched standard tensile round bar specimens under constant load conditions. The elementary transients associated with stress corrosion crack initiation were found to be embedded in the basic noise pattern coming from the oxide growth reaction on the tensile specimen. Thus a simple calculation of standard deviations to identify localised corrosion phenomena under high temperature water conditions cannot be used. The changes in the track of power density spectra proved to be much more suitable to indicate stress corrosion crack initiation under high temperature water conditions.

Over the past decade, we have developed deterministic models for predicting materials damage due to stress corrosion cracking (SCC) in boiling water reactor (BWR) primary coolant circuits. These steady-state models have been applied to fixed state points of reactor operation to yield electrochemical corrosion potential (ECP) and crack growth rate (CGR) predictions. However, damage is cumulative, so that prediction of the extent of damage at any given time must integrate crack growth rate over the history of the plant. In this paper, we describe the use of the REMAIN code to predict the accumulated damage functions for major components in the coolant circuit of a typical BWR that employs internal coolant pumps. As an example, the effect of relatively small amounts of hydrogen added to the feedwater (e.g., 0.5 ppm) on the development of damage from a 0.197-in. (0.5-cm) intergranular crack located at the exit of an internal pump was analyzed. It is predicted that hydrogen additions to the feedwater will effectively suppress further growth of the crack. We also report the first predictions of the accumulation of damage from SCC for a variable power operating cycle. We predict that the benefits of hydrogen water chemistry (HWC), as indicated by the behavior of a single crack under constant environmental conditions, are significantly muted by changes in reactor power. [S0094-9930(00)01301-9]