Fissile fuel producing blankets for both D-D and D-T fusion reactors are designed based on a slurry concept. In the designs, the blanket is composed of a slurry of ThO2 particles carried by heavy water. The slurry serves both to cool the reactor and to breed fissile fuel. Neutronic and photonic calculations showed that the slurry blankets achieved performance comparable to alternative concepts (moltensalts, fixed fertile material). For the slurry concept to be useful for a D-T reactor, a neutron multiplier needed to be used. The fast fission rate in the slurry blankets was small. Fission of the bred fissile material can be limited by removal of the ThO2 particles for processing after 5–10 days of irradiation.