It has been generally accepted that nuclear power (NPP) is suiable for power supply in korea because of its economical profits and pollution-free energy. When designing or operating a NPP. The main points to be home in mind are the hazards of and protection against an uncontrolled release of the large quantities of radioactiv substances which are always generated in a nuclear reactor while it is in iperation. Multiple independent safety systems are provided which should prevent this from occurring. Thus fire prevention measures in NPP follow the “Defense-in-depth” concept. This study aims to suggest the fire prevention measures and to demonstrate information which is needed for NPP planning and its safety assessment. The findings of this study can be used as useful data for fire protection plannings at the first phase of NPP design.