A flow coupler is considered as an alternative to the conventional primary pump in a liquid-metal fast breeder reactor (LMFBR). A conceptual design of a flow coupler combined with an intermediate heat exchanger in a pool-type LMFBR was done. Based on this design, a one-tenth-scale flow coupler model was built and successfully operated in a high-temperature sodium loop. To estimate the flow coupler characteristics, a quasi-one-dimensional code was developed. From these studies, the flow coupler pump concept appears to be feasible for actual use in an LMFBR.