[en] The future supply/demand structure of total and electrical energy has been analyzed, and the sectoral energy demand forecasts for industrial, residential, transportational, and other sectors have been attempted in this study. According to the firmly established nuclear power program, 6 nuclear units by 1986 and 13 nuclear units by 1991 will be in operation in Korea. However, no official nuclear power program has been established yet beyond 1991. Therefore, the extended nuclear power planning in the years to come after 1991 has been analyzed strategically based on the supply/demand views of total energy, nuclear fuel cycle and technical manpower requirements. In addition, the optimum reactor mix scenarios among PWR, HWR and FBR have been formulated and evaluated by looking at the longterm views of both required nuclear technology developments contributing to directly domestic commercialization and the core nuclear technologies to be developed intensively with high priority. From the supply/demand view points of nuclear fuel cycle requirements, the FBR operation before the year 2000 in Korea has been resulted in economical justification. Furthermore, assuming that the FBR operation would be delayed until the year 2010, the thermal recycle possibilities of the separated plutonium or uranium from thermal reactors also have been analyzed in a sense of spent fuel storage and waste disposal. (Author)