The Japan Sodium-cooled Fast Reactor (JSFR) adopts a double boundary for all sodium components. In this paper, design measures are investigated against a secondary sodium fire inside the reactor building, which might be assumed as design extension conditions. Candidate sodium fire measures for the secondary sodium systems compared in terms of safety are the sodium drain, nitrogen injection, pressure release valve, catch pan, and drain system for leaked sodium. Various sodium fires in the steam generator room have been analyzed by the SPHINCS code to evaluate the performance of the candidate sodium fire measures.