One of the potentially attractive applications of nuclear fusion is to breed fissile fuel for use in fission reactors. A fusion-fission breeder is examined, based on four unique concepts: operation in a non-power-producing mode, a low technology (low pressure and temperature) aqueous self-cooled blanket for breeding fissile fuel, the spherical torus confinement scheme (low-aspect-ratio tokamak), and the catalyzed deuterium-deuterium (D-D) fuel cycle. The breeding of fissile fuel is accomplished by dissolving a uranium salt, i.e., uranyl nitrate, in heavy water that cools both the first wall and blanket. The use of the catalyzed D-D fuel cycle eliminates the need for tritium breeding. The neutron wall loading for this reactor is only ∼0.5 MW/m2, and the fusion power output is ∼1000 MW(thermal). Analysis of this novel reactor concept indicates a fissile breeding ratio of 1.34 fissile atom/source neutron using a 15-cm beryllium moderator/multiplier region and 7 mol% uranyl nitrate in the heavy water. A typical reactor using this blanket can produce more than 7400 kg of plutonium per operating year. This concept can provide fissile fuel at a cost that is comparable to previous fusion breeder designs but at a capital cost of about one-third that of the previous designs.