ROLE OF IRRADIATION IN STRESS CORROSION CRACKING

Abstract

A growing concern for electric power utilities worldwide has been degradation in core components in nuclear power reactors, which make up ~17% of the world’s electric power production. Service failures have occurred in boiling water reactor (BWR) core components and, to a somewhat lesser extent, in pressurized water reactor (PWR) core components consisting of iron- and nickel-base stainless alloys that have achieved a significant neutron fluence in environments that span oxygenated to hydrogenated water at 270–340°C. Because cracking susceptibility is a function of radiation, stress and environment, the failure mechanism has been termed irradiation-assisted stress corrosion cracking (IASCC). Initially, the affected components have been either relatively small (bolts, springs, etc.) or designed for replacement (fuel rods, control blades, or instrumentation tubes). In the last decade, there have been many more structural components (PWR baffle bolts and BWR core shrouds) that have been identified to be susceptible to IASCC. Recent reviews [1 5] describe the current knowledge related to IASCC service experience and laboratory investigations and highlight the limited amount of wellcontrolled experimentation that exists on well-characterized materials. This lack of critical experimentation and the large number of interdependent parameters make it imperative that underpinning science be used to guide mechanistic understanding and quantification of IASCC.