Long-term embrittlement of cast duplex stainless steels in LWR systems

Technical Report · Mon Jul 01 00:00:00 EDT 1991

DOI:https://doi.org/10.2172/5576472· OSTI ID:5576472

Chopra, O K ^[1]

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1. Argonne National Lab., IL (USA)

This progress report summarizes work performed by Argonne National Laboratory on long-term embrittlement of cast duplex stainless steels in LWR systems during the six months from April 1990 to September 1990. A procedure and correlations are presented for predicting fracture toughness J-R curves and impact strength of aged cast stainless steels from known material information. Fracture toughness of a specific cast stainless steel is estimated from the extent and kinetics of thermal embrittlement. The extent of thermal embrittlement is characterized by the room-temperature normalized'' Charpy impact energy. A correlation for the extent of embrittlement at saturation,'' i.e., the minimum impact energy that would be achieved by the material after long-term aging, is given is terms of a material parameter, {phi}, which is determined from the chemical composition. The fracture toughness J-R curve for the material is then obtained from correlations between room-temperature Charpy-impact energy and fracture toughness parameters. Fracture toughness as a function of time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which are determined from chemical composition. A common lower-bound'' J-R curve for cast stainless steels with unknown chemical composition is also defined for a given material specification, ferrite content, and temperature. Examples for estimating impact strength and fracture toughness of cast stainless steel components during reactor service are described. Mechanical-property degradation suffered by cast stainless steel components from the decommissioned Shippingport reactor has been characterized. The results are used to validate the correlations and benchmark the laboratory studies. Charpy-impact, tensile, and fracture toughness data for materials from the hot-leg shutoff valve and cold-leg check valves and pump volute are presented. 37 refs., 53 figs., 9 tabs.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Div. of Engineering Research; Argonne National Lab., IL (United States)
• Sponsoring Organization: NRC; Nuclear Regulatory Commission, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5576472
• Report Number(s): NUREG/CR-4744-Vol.5-No.2; ANL--91/10; ON: TI91015983
• Country of Publication: United States
• Language: English

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