ABSTRACT
Until the 1970s, many of the corrosion problems in nuclear boiling water reactors (BWRs) were related to stress corrosion cracking (SCC), particularly to intergranular SCC (IGSCC). This was explained by the fact that austenitic steels undergo chromium carbide precipitation at grain boundaries when heated in the 600–700°C interval for a certain period. This phenomenon is known as sensitisation and such precipitation produces chromium depleted zones next to the precipitates, leading to a higher corrosion rate at grain boundaries compared to the steel matrix. This, along with the residual and operational stresses and impurities of the demineralised water used in this type of reactor at 288°C and 8 MPa pressure, contribute to the IGSCC phenomenon.
