A new nickel-based alloy for Molten Salt Reactors (MSR) using chloride salts: Design and characterization

Structural materials for molten-salt fast neutron reactors (MSRs) need to exhibit excellent mechanical properties at high temperatures and be able to resist corrosion by chloride salts and neutron irradiation. This study presents design considerations for a new class of nickel-based alloys, exemplified by Nimolloy-202. This alloy is defined its high molybdenum content (20 wt%), the absence of chromium and iron, and its hardening by γ’ phase (Ni₃(Al, Mo, Ti)) nano-precipitation which improves both mechanical properties and irradiation resistance. Nimolloy-202 demonstrates excellent corrosion resistance in purified binary NaCl-MgCl 2 salt at 600 °C for one week (168 h) under argon flow. Microstructural characterizations confirm the precipitation of nano- γ’ with a density approaching 10 23 m −3 . Their strengthening effect on the material is quantified and modeled. Collectively, these results highlight the potential of chromium-free Ni-Mo alloys for fast neutron chloride salt MSRs. Furthermore, these alloys, which can also be used as coatings, could be of interest to solar power plants that operate with chloride salts.