To improve the integrity of the liquid-metal fast breeder reactor steam generators, a concentric protective barrier, known as a protector tube, has been introduced around each bayoneted heat transfer tube. In the event of a water-to-sodium leak, this protector tube is expected to contain the sodium-water reaction effects resulting from medium to large leak rates and, for small leaks, to retard damage propagation to adjacent heat transfer tubes prior to leak detection, and thus allow sufficient time for an orderly shutdown of the steam generator. The proof-of-principle tests reported in this paper have demonstrated the advantages of the protector tube concept.