System analysis was performed to evaluate the economics and to calculate the material flows for Korean nuclear fuel cycle up to 2030. As the future constraints of nuclear are the limitation of natural uranium resources and the adequate waste management, the study focused on the uranium saving technologies such as the reprocessing of spent fuels, the recycling of recovered uranium and plutonium, the nutual complement between PWR and PHWR, and the effects of the introduction of FBRs. To simulate the Korean situation properly, time-dependent techno-economic parameters and the scaling effects for the localizable fuel cycle components were reflected. The levelized discounted fuel cycle costs were calculated for the oncethrough cycle, the reprocessing cycles and the tandem cycles of various options. Several material flows were calculated for the future conditions, also. The reprocessing cycle becomes cheaper than the once-through cycle from 2015 with the capacity of 800 ton/yr or more. The tandem cycle is more economical than the once-through cycle beginning over the range of 2000-2020 years. In view of economy and safety, the reprocessing and recycling of spent fuel is inevitable and it have to be carried out as soon as possible when there is an incentive compare to the conce-through cycle. The timing is expected to be the early 2010s. Because of the uranium resource limitation and greenhouse effect, the time of introduction of FBRs should be in 2020s or earlier.