The Republic of Korea (ROK) has enjoyed rapid economic growth and development over the last 30 years. Rapid increases in energy use-especially petroleum, natural gas, and electricity, and especially in the industrial and transport sectors-have fueled the ROK's economic growth, but with limited fossil fuel resources of its own, the result has been that the ROK is almost entirely dependent on energy imports. The article that follows summarizes the recent trends in the ROK energy sector, including trends in energy demand and supply, and trends in economic, demographic, and other activities that underlie trends in energy use. The ROK has been experiencing drastic changes in its energy system, mainly induced by industrial, supply security, and environmental concerns, and energy policies in the ROK have evolved over the years to address such challenges through measures such as privatization of energy-sector activities, emphases on enhancing energy security through development of energy efficiency, nuclear power, and renewable energy, and a related focus on reducing greenhouse gas emissions. The assembly of a model for evaluating energy futures in the ROK (ROK2010 LEAP) is described, and results of several policy-based scenarios focused on different levels of nuclear energy utilization are described, and their impacts on of energy supply and demand in the ROK through the year 2030 are explored, along with their implications for national energy security and long-term policy plans. Nuclear power continues to hold a crucial position in the ROK's energy policy, but aggressive expansion of nuclear power alone, even if possible given post-Fukushima global concerns, will not be sufficient to attain the ROK's "green economy" and greenhouse gas emissions reduction goals. (C) 2011 Elsevier Ltd. All rights reserved.