Corrosion and precipitation effects in a forced-convection Pb-15.7Li loop

The helium-cooled lithium lead (HCLL) concept for blankets is based on the application of the liquid breeder Pb-15.7Li, which is in direct contact with the structural components, e. g., RAFM steels. Corrosion attack of the structural material is always present and is mainly governed by the operation temperature and flow velocity of the liquid breeder. At high flow velocities, high dissolution rates of ca. 400 mu m/year were evaluated at 823 K (550 degrees C) and showed a high amount of corrosion products in the Pb-15.7Li. In a test blanket module (TBM) system or also in a testing loop, e. g., the PICOLO loop of KIT, these components are transported with the breeder flow to sections with cooler temperature and will form precipitates due to oversaturation. Effects such as deposition, precipitate formation and transport were less considered in former compatibility testing of RAFM steels (Eurofer) in flowing Pb-15.7Li and test evaluation. However, such formed particles may seriously affect safe and reliable operation of TBM systems. Analytical and modeling work concerning the impact of corrosion products was started and results obtained during PICOLO operation will be presented. Effects observed will also be discussed with respect to further testing needs for model development including their validation as predictive tools for TBMs with a view to DEMO and testing/qualification in ITER. (C) 2013 Elsevier B.V. All rights reserved.