Detection of stress corrosion cracking in a simulated BWR environment by combined electrochemical potential noise and direct current potential drop measurements

Abstract

Stress corrosion cracking (SCC) is one of the most important degradation mechanisms in light water reactor structural materials. In situ corrosion monitoring tools with the capability to detect SCC initiation in high temperature water environments would be important to identify critical conditions; the measurement of electrochemical noise (EN) could be such a tool. Laboratory investigations have indicated that detection of SCC initiation in austenitic stainless steel by EN measurements may be possible under simulated boiling water reactor (BWR) conditions, but further tests with an independent online SCC detection method were required to confirm these preliminary results. Therefore, the reversed direct current potential drop and EN techniques were simultaneously applied during SCC initiation tests in a simulated BWR environment on AISI 304 stainless steel notched compact tension and round bar specimens. It has been shown that early SCC detection by electrochemical potential noise measurements is possible in oxygenated high temperature water, at least under stable and stationary laboratory conditions. It was also concluded that in high purity water with very low conductivity, a short distance between specimen surface and reference electrode is crucial to achieve high detection sensitivity.