Reactor system design and safety studies at Atomics International have focused on the selection of a core configuration for the Prototype Large Breeder Reactor that has inherent “nonenergetic” responses to postulated core disruptive accidents. These studies have led to the selection of a non-conventional heterogeneous design, referred to as the bullseye core, as the preferred concept. The nuclear design characteristics and economics of this bullseye core are compared to those of an optimized, conventional liquid-metal fast breeder reactor core configuration, referred to as the regular core. A reduced sodium void worth and an enhanced voiding incoherence are attained by the introduction of internal blanket regions in the bullseye core. The bullseye core total energy costs are shown to be acceptable considering the significant improvement in licensability due to reduced core energetics.