CAREER: Understanding the Synergistic Effects of Irradiation and Molten Salt Corrosion on NiCr Alloys

NONTECHNICAL SUMMARY Nuclear energy contributes around 20% of the U.S. electricity portfolio. As climate change pushes many countries to pursue clean energy, and solar, wind, and other renewable resources might not be reliable enough to keep up with the energy demand, nuclear power is promising to fill the gap for a sustainable clean energy transition. Advanced reactors that rely on the application of molten salts are being under active investigation due to their major advantages in safety and efficiency. However, structural materials in molten salts are susceptible to failure due to extreme conditions, including high temperatures (higher than 700 degrees Celsius), radiation exposure (neutron and fission fragments), and corrosive environments (molten salts). Through this award, funded by the Condensed Matter and Materials Theory Program in the Division of Materials Research at NSF, the PI aims to address a particular challenge regarding the synergistic effect of radiation and high-temperature corrosion on Ni-based alloys, where experimental data sometimes shows conflicting conclusions regarding the role of radiation in mediating the corrosion of alloys. This project goal will be achieved based on a computational perspective, where multi-scale computational methods will be used and developed, and the results will be complemented by experimental characterization. This project also emphasizes educational and training opportunities for students and the public. Undergraduate and graduate students will gain hands-on research experiences with cutting-edge computational techniques, expanding their knowledge and skills in materials science research. Outreach activities will be targeted toward local pre-college students in Centre County School District, Pennsylvania, especially those from underrepresented minority communities. Additionally, a series of educational video episodes that feature various aspects of nuclear energy will be produced and disseminated via online channels to the public. These activities contribute to fostering the future workforce for the clean energy sector and enhancing awareness of the importance of nuclear energy and associated challenges. TECHNICAL SUMMARY The interest in advanced nuclear reactors that rely on molten salt applications continues to grow due to their promise to be part of an energy solution for decarbonization to combat climate change. High-temperature molten salt (fluoride salt as a major candidate) corrosion and irradiation of structural materials (Ni-based alloys as a major candidate) is a life-limiting problem for long-term reliability. However, a fundamentals-based predictive capability for evaluating molten salt corrosion of structural materials under irradiation is seriously lacking. A particular challenge is the synergistic effect of radiation and high-temperature corrosion, where experimental data sometimes shows conflicting conclusions regarding the role of radiation in mediating the corrosion of alloy. This project aims to address this conundrum from a computational perspective, complemented by experimental characterization. A multi-scale strategy which encompasses first-principles calculations based on density function theory, interface dynamics based on reactive molecular dynamics, and microstructural evolution based on kinetic Monte Carlo, is proposed. Not only can this multi-scale strategy address the hypotheses on how radiation and corrosion are coupled, it also provides the tools to obtain an evolutional picture of microstructural changes that is based on fundamental understanding. These efforts will contribute to advanced reactor development and broader fields such as functional materials synthesis, thermal storage, and chemical refinement. The two major research objectives include i) advancing the fundamental understanding of active molten salt corrosion mechanisms and ii) understanding the synergetic effects of radiation and corrosion at the alloy-salt interface. Integrated with these research objectives, the major educational objectives include cultivating the next generation of professionals for the clean energy sector while also raising awareness about the significance of nuclear energy and its associated challenges. Both undergraduate and graduate students will acquire practical research skills using state-of-the-art computational techniques, thereby broadening their expertise in materials science research. Outreach efforts will be directed toward pre-college students in the local school district, with a particular focus on those from underrepresented minority communities. Furthermore, a collection of educational video episodes highlighting different facets of nuclear energy will be produced and shared online for public dissemination. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.