Long-term corrosion behavior of EUROFER RAFM steel in static liquid Pb-16Li at 550 °C

Abstract

Liquid Pb-16Li eutectic alloy is the tritium breeding material in several breeding blanket concepts for European DEMO reactor, which are the Helium-Cooled Lithium-Lead (HCLL), the Water-Cooled Lithium-Lead (WCLL) and the Dual-Coolant Lithium-Lead (DCLL). RAFM (Reduced-Activation Ferritic/Martensitic) steels are considered as structural materials for breeding blankets in fusion reactors and EUROFER steel (9Cr-1.1W-0.2 V) is the European current choice for DEMO. Moreover, the WCLL European Test Blanket Module (TBM) to be installed in ITER will be manufactured in EUROFER. Here, the chemical compatibility of EUROFER in Pb-16Li is a major issue due to the dissolution of the material at high temperature in the liquid metal. In this work the corrosion of EUROFER in static Pb-16Li melt was investigated at 550 °C up to 8000 h of exposure to approximate low-flow WCLL blanket conditions. SEM-EDX analysis were performed on corroded samples to assess morphology and compositional changes occurring during the exposure. The corrosion was numerically evaluated by weight loss on samples exposed to various exposure times (2000, 4000 and 8000 h) and the corrosion rate for one year of exposure (8760 h) was extrapolated. The analysis by SEM-EDX showed that EUROFER mostly dissolved uniformly with a depletion of Cr and an enrichment of W at the near interface. The analysis of the weight loss provided an extrapolation of the corrosion rate of 18 μm/yr at 550 °C.