Recent heavy-ion fusion power plant studies in the US

Summary

The United States Department of Energy (DOE) sponsored two studies of inertial fusion energy (IFE) electric power plants, one led by McDonnell Douglas Aerospace (MDA) and the other led by W. J. Schafer Associates (WJSA). These studies, which were completed in March of 1992, included the conceptual design and analysis of two KrF-laser and two heavy-ion-driven power plants. The reactor and driver designs for the heavy-ion power plants are described in this paper. The MDA team design, Prometheus-H, features a wetted-wall chamber, a compact induction linac driver, and channel propagation for beam delivery. The single-beam driver uses storage rings to accumulate a series of pulses before delivery to the target. The use of storage rings and a folded linear section results in a compact footprint and significant cost savings compared to a straight multiple-beam linac. Fourteen beams of doubly-charged, 4 GeV Pb ions are used to deliver 7 MJ on the target at a pulse repetition rate of 3.5 Hz with an overall driver efficiency of 21%. The channel propagation mode requires only two small, diametrically opposed holes through the blanket and first wall; this approach maximizes the wall coverage and minimizes radiation leakage and contamination of the beamlines. Th resulting target gain is 103 for a yield of 719 MJ per pulse. The Prometheus chamber has a Pb-cooled, porous SiC first wall and a He-cooled Li₂O breeding blanket. The blanket structural material is low-activation SiC. The thermal conversion efficiency is 43%, and the net electric power is 1000 MWe. The WJSA team design, Osiris, uses a wetted-wall chamber, a multiple-beam induction linac driver, and ballistic focus with auto-neutralization. The driver design is conservative in that it uses singly charged ions and does not use beam combination or splitting. Twelve beams are close-packed in order to use common cores and focusing magnets. The accelerator costs were reduced by operating at spacecharge-limited current density and standardizing the quadrupole and inductor designs. In this case, twelve beams of 3.8 GeV Xe ions provide a total of 5 MJ at a pulse repetition rate of 4.6 Hz. The overall driver efficiency is 28%, the target gain is 87, and the yield is 432 MJ per pulse. The Osiris chamber uses a flexible, porous carbon/carbon fabric to contain the flow of the molten salt Flibe, which serves as the primary coolant and breeding material. The vacuum vessel structure is a carbon/carbon composite. The thermal conversion efficiency is 45%, and the net electric power is 1000 MWe.