Session: MF-06-02 Materials and Technologies for Nuclear Power Plants II

Paper Number: 61055

Start Time: Tuesday, July 13, 2021, 08:00 PM

61055 - A Discussion of Strength Reduction Factor Development for Thermal Aging Effect on Nuclear Structural Alloys 

In consideration of structural alloy property deterioration during long-term exposure to elevated temperatures, the yield and ultimate tensile strength reduction factors are provided in the Boiler and Pressure Vessel Code Section III for nuclear reactor component design and operation analysis.  Because the Gen IV reactor requirement of 40 ~ 60 years of service makes it difficult to acquire such long exposure test data for developing the reduction factors, they must be derived from test data with relatively short exposure by some effective approaches.  A novel physically-based model approach is recently developed, in which constituents of the tensile strength of 9Cr-1Mo-V are first identified and related to its definite microstructural features, then established methods are adopted to simulate the microstructural evolution, and finally the physically-based model is assembled with test-data-calibrated parameters to generate the yield and ultimate tensile strength reduction factors covering elevated temperature exposure for up to 57 years.  It is undoubtedly a trailblazing development that will, if proven reliable, lead to a paradigm shift in predicting property evolution of many other alloys.  Because of its novelty, great potential, and debut application to Section III that concerns nuclear safety, it inevitably warrants objective, impartial, and thorough technical scrutiny in comparison with convention approaches.  In the present paper, the novel and conventional approaches are discussed.  Improvements deemed necessary to the novel approach are suggested for its desired expansion of application to other alloys, particularly for its adoption to applications in nuclear structural component design and analysis.

Presenting Author: Weiju Ren Oak Ridge National Laboratory

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