United States Nuclear Regulatory Commission - Protecting People and the Environment

Review of the Margins for ASME Code Fatigue Design Curve - Effects of Surface Roughness and Material Variability (NUREG/CR-6815, ANL-02/39)

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Publication Information

Manuscript Completed: December 2002
Date Published:
September 2003

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

W.H. Cullen, Jr., NRC Project Manager

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

The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. The Code specifies fatigue design curves for structural materials. However, the effects of light-water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Existing fatigue strain-vs. -life (ε-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This report provides an overview of the existing fatigue ε-N data for carbon and low-alloy steels and wrought and cast austenitic stainless steels (SSs) to define the effects of key material, loading, and environmental parameters on the fatigue lives of the steels. Experimental data are presented on the effects of surface roughness on the fatigue life of these steels in air and LWR environments. Statistical models are presented for estimating the fatigue ε-N curves as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are discussed. Data available in the literature have been reviewed to evaluate the conservatism in the existing ASME Code fatigue evaluations. A critical review of the margins for ASME Code fatigue design curves is presented.

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