Abstract In the water cooled lead lithium (WCLL) blanket liquid lead lithium PbLi is used as breeder, neutron multiplier, and as heat transfer medium. The released heat is removed by water that flows at a pressure of 155 bar through cooling pipes immersed in the liquid-metal pool. In order to withstand disruption-induced forces and water pressure in case of accidental conditions, the breeder zone is stiffened by internal plates that form rectangular ducts in which the liquid metal is confined. Numerical simulations have been performed to predict liquid metal flows in model geometries for WCLL blankets under the influence of external magnetic fields. In the analysis the flow is driven by an applied pressure gradient or by buoyancy due to the presence of volumetric heat sources in the fluid and heat removal at the water-cooled pipes. For strong magnetic fields the flow exhibits several quasi-2D cores with jumps in core velocity across thin internal layers tangent to the cooling pipes.