Corrosion of Molybdenum-Based and Ni-Mo Alloys in Liquid Bismuth-Lithium Alloy

Bismuth-lithium alloys are considered primary candidates for the reductive extraction step in the on-line reprocessing of molten salt reactor fuel. The corrosion behavior of molybdenum-based alloys and Hastelloy((R)) B-3 alloy (taken for comparison) was examined here in a liquid Bi-Li (5 mol.%) alloy at 650 degrees C. MoW10, MoW30, and TZM corrosion-resistant alloys were studied as prospective construction materials for holding liquid bismuth-lithium alloy. Rates of corrosion were determined by the gravimetric method as well as by chemical analysis of corrosion products formed in liquid-phase Bi-Li alloy. The microstructure and chemical composition of samples of the materials and Bi-Li alloys containing the corrosion products after the tests were determined using inductively coupled plasma-atomic emission spectroscopy, X-ray fluorescence analysis, scanning electron microscopy, and energy dispersive spectroscopy. TZM molybdenum-based alloy corrodes in the bismuth-lithium alloy due to the formation of a zirconium-bismuth intermetallic compound, which passes into the liquid phase. The corrosion rates of MoW10, MoW30, and TZM alloys at 650 degrees C were 16, 16, and 23 mu m/year, respectively. Hastelloy((R)) B-3 alloy, despite its high molybdenum content, was subjected to severe corrosion in liquid Bi-Li alloys due to dissolution of nickel in liquid bismuth. The corrosion rate of this alloy was 14 mm/year.