High breeding with light water cooling has been studied for decades, though is not easy to be achieved. The main obstacle is the moderating effect of light water, which softens the neutron spectrum. To harden the neutron spectrum and thereby to enhance the fuel utilization or even to achieve breeding with light water cooling, the tight-lattice assembly was proposed and applied to High Conversion LWRs. Nonetheless, none of them achieved high breeding. Until recently, the tightly packed fuel assembly (TPFA) is designed for the purpose of high breeding. The ratio of hydrogen atoms to heavy metal atoms (H/HM) in this assembly is significantly reduced to be less than 0.1. Super Fast Breeding Reactor (Super FBR) adopts TPFA and achieves breeding performance with compound system doubling time (CSDT) of 43 years. In this study, the breeder BWR core also applies TPFA and achieves CSDT of 50 years. BWR is one type of the most extensively built reactors in the world, with abundant operation experience and mature technologies. Breeder BWR is considered to be capable of being incorporated into the current BWR plants with a handful of modifications, thus obtaining optimal economy.