Calculation of Dissolution/Precipitation Rates in Flowing Eutectic Pb-17Li with the MATLIM code

Full text of publication follows: Pb-17Li alloy is considered as a coolant and liquid breeder in future fusion reactors. One major problem in nonisothermal liquid metal systems lies in the corrosion of their structural materials, consisting mainly of ferritic-martensitic and austenitic stainless steels. It is generally accepted that corrosion of steel components in flowing liquid Pb-17Li is ruled by dissolution/precipitation processes. A simple method has been developed to calculate the mass transfer in liquid metal loops. It is based on the use of mass transfer coefficients which determine the mass flux from the wall into the fluid and vice versa. These coefficients depend on a characteristic dimensionless thermo-hydraulic number, namely the Sherwood number, which itself depends under forced convection flow conditions on the Reynolds number and the Schmidt number. This is supplemented by the application of differential equations for dissolved steel components expressing the mass conservation law in the coolant channel in an integral form. The dissolution and precipitation rates determine then the evolution of the flow channel geometry along the loop and the flow velocity. The newly developed code MATLIM can routinely deal with multi-modular liquid metal loops. Thus, calculations have been done for the Pb-17Li loop PICOLO at Forschungszentrum Karlsruhe, based on iron solubility and diffusivity correlations of Feuerstein et al. The evolution of dissolution rates observed in the test section of the PICOLO loop for the martensitic steel EUROFER can be reproduced very good by code calculations. (authors)