United States Nuclear Regulatory Commission - Protecting People and the Environment

Void Swelling and Microstructure of Austenitic Stainless Steels Irradiated in the BOR-60 Reactor (NUREG/CR-7128)

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Publication Information

Manuscript Completed: June 2011
Date Published: November 2012

Prepared by:
Y. Chen,1 Y. Yang,2 Y. Huang,2 T. Allen,2
B. Alexandreanu,1 and K. Natesan1

1Argonne National Laboratory
Argonne, IL 60439

2University of Wisconsin-Madison
Madison, WI 53706

NRC Project Manager, A. S. Rao

NRC Job Code N6519

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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As nuclear power plants age and neutron fluence increases, detrimental effects resulting from radiation damage have become an increasingly important issue for the operational safety and structural integrity of core internal components. In this study, irradiated specimens of reactor core internal components were characterized by transmission electron microscopy. The specimens had been irradiated to 5.5-45 dpa in the BOR-60 reactor at a dose rate close to 10-6 dpa/s and temperature of about 320°C. No voids were observed in the austenitic stainless steels and nickel alloys at all doses. Despite the possibility that fine voids below the TEM resolution limit may be present, it was clear that void swelling was insignificant in all examined alloys up to 45 dpa. Irradiated microstructures of the studied alloys were dominated by a high density of Frank loops. The mean size and density of the Frank loops varied from one material to another, but saturated with increasing dose above ˜10 dpa. While no irradiation-induced precipitations were present below 24.5 dpa, fine precipitates were evident in several alloys at 45 dpa.

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