Behaviour of materials for accelerator driven systems in stagnant molten lead

Abstract The behaviour of a modified F82H martensitic steel (both uncoated and aluminised) and tungsten was evaluated by immersion tests in stagnant, oxygen-saturated 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 Accelerator Driven Systems (ADS), while tungsten is potentially suitable for a beam 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 Fe3O4, formed on the surface of the uncoated steel while the aluminised steel showed no significant alteration. On tungsten, a compact and adherent layer of WO3 formed and reacted with liquid lead leading to the formation of friable Pb–W–O ternary compounds. A two-step mechanism is proposed for interactions of metals and alloys exposed to oxygen-saturated molten lead: the first 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 surface.