The Current Status of Liquid Fuel and Material Technology Development for Chloride-Based Molten Salt Reactors (MSRs) at KAERI Part I. Liquid Fuel Fabrication and Natural Convection Loop Operation for Corrosion Characteristics

Chang Hwa Lee^*a, Dalsung Yoon^a, Taeho Kima^a,b

^aKorea Atomic Energy Research Institute, Daedoek-daero 989-111, Yuseong-gu, Daejeon 34057, Republic of Korea
^bDepartment of Nuclear Science and Technology, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea

Received 2025-02-10 ; Revised 2025-02-27 ; Approved 2025-03-14

Abstract

The efficient fabrication of uranium-based liquid fuels and the structural integrity of reactor materials are critical challenges for the deployment of chloride-based molten salt reactors (MSRs). As part of KAERI’s ongoing MSR development, this study investigates an optimized uranium chlorination process and a corrosion assessment of candidate structural materials under conditions more closely resembling actual reactor cores. To enhance process efficiency and scalability, metallic uranium was converted into uranium trihydride (UH₃) via hydriding, achieving 34.1% efficiency. UH₃ was chlorinated with ammonium chloride (NH₄Cl), yielding uranium trichloride (UCl₃) with a conversion rate over 98% and purity above 99%, as confirmed by ICP-OES. The UCl₃ was used to fabricate various uranium-based liquid fuels for MSR applications. Simultaneously, the corrosion behavior of SS304, SS316, and Hastelloy-N was evaluated using a natural convection loop filled with a NaCl–MgCl₂ eutectic salt mixture. The system operated for 500 hours at 500–580°C to replicate MSR conditions. Corrosion analysis revealed that SS304 suffered severe degradation, SS316 showed moderate resistance, and Hastelloy-N demonstrated superior stability, although some cold leg samples experienced mass gain due to corrosion product deposition. These findings provide key insights into optimizing liquid fuel synthesis and selecting corrosion-resistant materials for safe, long-term MSR operation.

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