AbstractKfK is working on the development of a selfcooled liquid metal blanket. The basic physics of MHD-flow, its effect on heat transfer and its consequences on the design are discussed. The MHD key problems of the KfK reference concept are identified: They consist of 3-dimensional effects and channel interactions. Whereas for single channel poloidal flow a relative broad basis of data exists, the knowledge of the key problems is poore. Theoretical and experimental work has been initiated therefore to quantify them. First results on single channel flow are presented.