A conceptual design study of small long-life nuclear power reactors used for a remote or isolated area has been performed. Lead as well as lead-bismuth is employed as the coolant, and both metallic and nitride fuels are investigated. There are some severe requirements on these reactors for operability, maintainability, safety, and proliferation resistance. Some important characteristics of the proposed designs [150 MW(thermal)] are the following: transportability between reactor factory and operation site; capability of long-life operation (12 yr) without refueling or fuel shuffling while maintaining burnup reactivity swing less than 0.1% Δk; negative total core coolant void coefficient of reactivity over all the burnup period; omission of intermediate heat exchanger; and a relatively large contribution of natural circulation.