Fracture Toughness and Crack Growth Rates of Irradiated Austenitic Stainless Steels (NUREG/CR-6826, ANL-03/22)

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Publication Information

Manuscript Completed: March 2003
Date Published: August 2003

Prepared by:
O.K. Chopra, E.E. Gruber, and W.J. Shack
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439

William H. Cullen, Jr., and Carol E. Moyer, NRC Project Managers

Prepared for:
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code Y6388

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Abstract

Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of reactor pressure vessels because of their superior fracture toughness properties. However, exposure to high levels of neutron irradiation for extended periods leads to significant reduction in the fracture resistance of these steels. Experimental data are presented on fracture toughness and crack growth rates (CGRs) of austenitic SSs irradiated to fluence levels up to 2.0 x 10²¹ n/cm² (E > 1 MeV) (≈3.0 dpa) at ≈288°C. Crack growth tests were conducted under cycling loading and long hold time trapezoidal loading in simulated boiling water reactor (BWR) environments, and fracture toughness tests were conducted in air. Neutron irradiation at 288°C decreases the fracture toughness of the steels; the data from commercial heats fall within the scatter band for the data obtained at higher temperatures. In addition, the results indicate significant enhancement of CGRs of the irradiated steels in normal water chemistry BWR environment; the CGRs for irradiated steels are a factor of ≈5 higher than the disposition curve proposed for sensitized austenitic SSs. The rates decreased by more than an order of magnitude in low-dissolved-oxygen BWR environment.