Summaries are described on the sodium combustion experiments conducted by HEDL(F1, F2, F4, F5), KfK, Cadarashe(IGNA402 & 2002, IGNA3602 & 3604), the former PNC, etc. The sodium fires of Almeria Solar Plant and ILONA Test Facility are taken up as the examples of large-scale accidents. Fast breeder reactor(FBR) safety considerations are discussed, with attentions paid to the integrity of steel liner and sodium-concrete reaction, in relation to the secondary sodium leakage of MONJU. The author suggests that injection of nitrogen gas is an effective measure against sodium fires, suppressing the temperature rises, chemical reactions and also surely excluding a hydrogen explosion in case of sodium-concrete reaction.