In-situ Monitoring of Micro-scale PWSCC of Ni-based Alloys in a Simulated Primary Water Chemistry of a PWR using an EN-DCPD Technique

Abstract

This work was conducted to establish an electrochemical noise (EN) measurement combined with a direct-current potential drop (DCPD) method, namely, an EN-DCPD technique, for in-situ monitoring of nano- or micro-scale crack initiation and the propagation of primary water stress corrosion cracking (PWSCC) of nickel based alloys, and to investigate its underlying mechanism. The EN signals of the potential and current were measured under various conditions of a simulated primary water chemistry of a pressurized water reactor (PWR), and the amplitude and frequency of the EN signals were analyzed in both the time and frequency domains. From the spectral and stochastic analyses, the effects of such experimental factors as the current application in DCPD, loading condition, temperature, and pressure of the primary water environment were found to be effectively excluded from the EN signals generated from the PWSCC propagation. From a stochastic analysis based on the shot-noise theory, the PWSCC propagation could be distinguished from the general corrosion, by considering the Weibull shape parameter.