Behaviour of materials for accelerator driven systems in stagnant molten lead

The behaviour of a modified F82H martensitic steel (both uncoated and alumi nised) and tungsten was evaluated by immersion tests in stagnant, oxygen-sa turated liquid lead at 793 K under an argon atmosphere, for exposure times up to 3700 h. The F82H steel is a candidate structural material for Acceler ator Driven Systems (ADS), while tungsten is potentially suitable for a bea m window working immersed in liquid lead. Layers of Me3O4 consisting of an inner sublayer with Me = Fe and Cr and an outer chromium-free sublayer of F e3O4, formed on the surface of the uncoated steel while the aluminised stee l showed no significant alteration. On tungsten, a compact and adherent lay er of WO3 formed and reacted with liquid lead leading to the formation of f riable Pb-W-O ternary compounds. A two-step mechanism is proposed for inter actions of metals and alloys exposed to oxygen-saturated molten lead: the f irst step is the solid phase oxidation of the base metal; the second is the interaction between liquid lead and the oxide layer formed on the metal su rface. (C) 2000 Elsevier Science B.V. All rights reserved.