MHD flow in liquid metal blankets with helical vanes

MHD flow in liquid metal blankets with helical vanes is discussed. The velocity profile and the MHD pressure drop in a pipe with a diametric turning vane under an axial magnetic field are derived with the assumption of fully developed conditions. The fluid flows helically along the vane with the velocity almost inversely proportional to the radius. Eddy currents flow radially in the fluid and then back through the outer wall and the vane. The radial current and the axial field cause a force in the circumferential direction, which resists the circumferential flow. Since the current intensity can be reduced by thinning the vane, the MHD pressure drop is low in a pipe with a thin vane. A reference design of a liquid metal blanket with a helical vane is made, and the required thickness of the vane is discussed from the viewpoint of structural strength. The temperature distribution is calculated and is compared with those of pipes without vanes. The vane is shown to keep the first wall temperature low with a small additional pressure drop. (author)