Special topics reports for the reference tandem mirror fusion breeder: Liquid metal MHD pressure drop effects in the packet bed blanket, volume 1

Magnetohydrodynamic (MHD) effects which result from the use of liquid metal coolants in magnetic fusion reactors include increases in the primary loop pressure drop and the hydrostatic pressure at the first wall of the blanket. In the reference fission-suppressed tandem mirror fusion breeder design concept the MHD pressure drop in flowing the liquid lithium coolant through an annular packed bed of beryllium/thorium pebbles is directly related to the required first wall structure thickness. As such, it is a major concern which directly impacts fissible breeding efficiency. Consequently, an improved model for the packed bed pressure drop was developed. By considering spatial averages of electric fields, currents, and fluid flow velocities the general equations were reduced to simple expressions for the pressure drop. An energy approach was used to bound the possible values of the constant, and thus the pressure drop. A survey of existing test facilities is presented.