[en] A specific feature of a fast reactor is the presence of sodium coolant. Liquid sodium is a combustible material and therefore if any leaks occur in the sodium loops, the escaping sodium may ignite, releasing energy and smoke. Sodium leaks and fires which have occurred in practice have not posed a threat to the nuclear or radiation safety of reactors. On the other hand, during the operation of thermal reactors, a number of serious fires have occurred, which caused extensive material damage and, it things had turned out badly, could have threatened reactor safety. In this paper, the authors present a comparative analysis of the risk of ordinary and sodium fires in nuclear power plants. The characteristics of sodium and other combustible materials used in nuclear power plants. The characteristics of sodium and other combustible materials used in nuclear power plants are analysed. The risk of different types of fires is considered taking into account features of specific reactor projects, including the location in the reactor building of fire protection systems and combustible material, the fire resistance of fire barriers (screening), and the operation of fire detection and extinguishing systems. Methods of safety probability analysis are employed. It is concluded that the use of sodium at nuclear power plants does not lead to an essential reduction in overall safety