Evaluating the Performance of HT9 Alloy Steel in NaCl-MgCl2 for Generation IV Nuclear Reactors

Abstract

The molten chloride salt-cooled high-temperature nuclear reactor, a promising Generation IV innovation, offers intrinsic safety features that improve operational reliability. This study examines the corrosion behavior of ferritic-martensitic (FM) stainless steel (HT9), a pivotal structural material, within the proposed coolant salt for chloride-based reactors: NaCl-MgCl₂.Static immersion tests at 550 °C were conducted over one, two, and three weeks under an argon environment. Results showed a time-dependent decrease in HT9 alloy steel's corrosion resistance, with pitting as the predominant form of corrosion damage. Redox control tests demonstrated that Mg treatment effectively reduced alloying element corrosion by more than 50%. This study provides crucial insights into the properties and corrosion behavior of the NaCl-MgCl₂ system, addressing a critical knowledge gap for advancing molten chloride salt-cooled reactors and enhancing the safety and reliability of these innovative Generation IV nuclear reactors.