Alloys for 1000°C Service in the Next Generation Nuclear Plant

Participants: G. S. Was, PI (with J. W. Jones and T. Pollock), D. Kumar and J. Kim, Graduate Students
SponsorU.S. Department of Energy, Nuclear Energy Research Initiative (NERI) , Idaho National Laboratory

The objective of the proposed research is to define strategies for the improvement of alloys for structural components, such as the intermediate heat exchanger and primary-to-secondary piping, for service at 1000°C in the He environment of the NGNP. Specifically, we will investigate the oxidation/carburization behavior and microstructure stability and how these processes affect creep. While generating this data, the project will also develop a fundamental understanding of how impurities in the He environment affect these degradation processes and how this understanding can be used to develop more useful life prediction methodologies. Our initial studies will focus on the mechanisms controlling the high temperature degradation of nickel-base alloy 617.

Understanding the degradation mechanisms will allow us to predict long-term behavior (to extrapolate lab results to long-term service performance) and to identify an effective approach to modify existing alloys for improved performance. To achieve the latter, we will also investigate two material modification strategies; alloy modifications that provide additional solid solution strengthening and reduce interdiffusion (and therefore creep), and grain boundary engineering to reduce creep. The alloy selection and materials requirements will be based on the Next Generation Nuclear Plant Materials Selection and Qualification Program Plan (INEEL/EXT- 03-01128) and the research plan will be closely integrated with, and designed to complement ongoing and planned studies on alloy 617 at INEEL and ORNL. The research will also provide a platform for educating students in the area of nuclear reactor materials and related issues.