A preconceptual engineering design has been developed for the3He Target/Blanket (T/B) System for the Accelerator Production of Tritium Project. This concept uses an array of pressure tubes containing tungsten rods for the neutron spallation source and3He gas contained in a metal tank and blanket tubes as the tritium production material. The engineering design is based on a physics model optimized for efficient tritium production. Principle engineering consideration were: provisions for cooling all materials including the3He gas; containment of the gas and radionuclides; remote handling; material compatibility; minimization of3He, D2O, and activated waste; modularity; and manufacturability. The design provides a basis for estimating the cost to implement the system.