Materials Challenges for Molten Salt Reactors

Abstract

While molten salt reactors offer several mechanical and nuclear design advantages relative to conventional nuclear power systems, there are materials issues that need to be addressed. Demonstrating materials performance is further challenged by currently qualified structural materials, which are not optimized for use in molten salts. In this paper, we review selected alloys for their corrosion, creep, and stress corrosion cracking performance in molten salts and identify areas for research as well as potential solutions. For example in 316 stainless steel exposed to FLiBe, general corrosion is accelerated with increasing temperature but shows acceptably slow rates with redox control of the salt. However, corrosion performance needs to be verified with the more creep resistant 316H grade. Furthermore, nontraditional solutions such as cladding offer further corrosion protection. Creep performance of 316H is likely satisfactory for many designs but matching weld filler metals can be limiting and require additional testing. Furthermore, more creep resistant alloys such as Alloy 617 and Alloy 709, an advanced austenitic stainless steel, may be required for the hottest and most highly stressed components. The risk for stress corrosion cracking can be minimized via careful control of the salt composition (e.g. minimizing oxidants) but significantly more research is needed to demonstrate resistance of alloys, heat affected zones, and their weld filler metals in molten salts where SCC mechanisms such as dealloying are likely. Keywords: Molten Salt Reactors, Materials, Alloys, Corrosion, Creep, Stress Corrosion Cracking This manuscript has been co-authored by UChicago Argonne LLC under Contract No. DE-AC02-06CH11357 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan: (http://energy.gov/downloads/doe-publicaccess-plan).