Review of liquid metal corrosion issues for potential containment materials for liquid lead and lead-bismuth eutectic spallation targets as a neutron source

Lead (Pb) and lead-bismuth eutectic (44Pb-56Bi) have been the two primary candidate liquid metal target materials for the production of spallation neutrons. Selection of a container material for the liquid metal target will greatly affect the lifetime and safety of the target subsystem. For the liquid lead target, niobium-1 wt% zirconium (Nb-1Zr) is a candidate containment material for liquid lead, but its poor oxidation resistance has been a major concern. In this paper, the oxidation rate of Nb-IZr was studied based on the calculations of thickness loss resulting from oxidation. According to these calculations, it appeared that uncoated Nb-IZr may be used for a 1-year operation at 900°C at Po(2) = 1 x 10^-6 Torr, but the same material may not be used in argon with 5-ppm oxygen. Coating technologies to reduce the oxidation of Nb-IZr are reviewed, as are other candidate refractory metals such as molybdenum, tantalum, and tungsten. For the liquid lead-bismuth eutectic target, three candidate containment materials are suggested, based on a literature survey of the materialsʹ compatibility and proton irradiation tests: Croloy 2-1/4, modified 9Cr-1Mo, and 12Cr-1Mo (HT-9) steel. These materials seem to be used only if the lead-bismuth is thoroughly deoxidized and treated with zirconium and magnesium.