This study aims to introduce the current role of nuclear power in Korea as the economic resource and low carbon emitter using WASP-IV (Wien Automatic System Planning Package) code for the long term electric power expansion planning. The current role of nuclear power in the long term power expansion is expressed as the portion of installed or generation capacity comparing coal, LNG or renewables. Analysis on the nuclear role is carried out in terms of the total power system operation cost, benefit of carbon reduction and stable power supply. The objective and approach of this study are to compare the different types of scenarios in terms of the system cost changes, CO2 emission reduction and system reliability. The results from this analysis are useful for the Korean government in charge of long term energy policy to go over what kinds of role can each electric resource play and what are the best way to solve the triangular dilemma as economics, environmental friendliness, stable supply of the future energy policy. (C) 2008 Elsevier Ltd. All rights reserved.