Al-based Barrier Development for Nuclear Fusion Applications

摘要

In the HCLL (He-cooled Lithium-lead) design of TBM's (Test Blanket Modules) for a future fusion power plant, Pb-15.7Li is used as liquid breeder which is in direct contact with the structure material, e.g. EUROFER steel (European ferritic steel). Compatibility testing showed that high corrosion attack appears and that the dissolved steel components form precipitates with a high risk of system blockages. A reliable operation needs coatings as corrosion barriers.An earlier developed Hot-Dip Aluminization (HDA) process has shown that Al-based scales can act as anti-corrosion as well as tritium (T) permeation barriers. However, disadvantages of HDA-process initiated the search for advanced coating technologies. Meanwhile two electro-chemically based processes for deposition of Al scales were successfully developed. The first (ECA = Electro-Chemical Al-deposition) is working with an organic electrolyte and the second one (ECX = Electro-Chemical X-metal deposition) is based on ionic liquids and is not restricted to only Al-deposition. Coatings in the um-range were deposited homogeneously with exact controllable thicknesses. Metallurgical investigations and SEM/EDX-analyses showed the successful generation of protective scales and compatibility testing demonstrated the barrier function in Pb-15.7Li.