Localized Deformation as a Mechanism for IASCC in Light Water Reactors

Gary Was

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gsw@umich.edu

1921 Cooley

T: (734) 763-4675

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The purpose of this project is to establish that localized deformation in irradiated LWR core internals is a primary factor in irradiation assisted stress corrosion cracking (IASCC). This mode of degradation is a continuing problem in existing LWRs and is expected to be a more serious problem in advanced LWRs and water-cooled Generation IV concepts such as the supercritical water reactor. Progress in understanding the mechanism driving IASCC has been slow due to the difficulty in unfolding the various contributions to the irradiated microstructure that may contribute to IG cracking. However, data from both unirradiated and irradiated austenitic alloys point toward slip localization in the form of intense, dislocation channels as a common factor in the cause of IG cracking in these alloys. The plan of work seeks to establish the role of localized deformation using a series of carefully chosen alloys and a systematic set of experiments designed to quantify the degree of slip localization as a function of alloy stacking fault energy (SFE) and dislocation channeling following irradiation. Experiments in BWR normal water chemistry will provide the link between slip localization and IASCC susceptibility. A primary outcome of the project is to provide guidance for the development of mitigation measures for IASCC.