The present paper aims to propose an original steam generation system, which resulted suitable for the application to the secondary loops of lead-cooled fast reactors: reaction heat is extracted from the lead by means of a coolant under vapor phase, thanks to both an external feed-water boiling and special bayonet tubes in the primary-secondary fluid heat exchangers. The performance of three different steam cycles equipped with this system were evaluated for the secondary loop of ALFRED 300 MWth demonstrator. The bayonet heat exchangers were sized through a coordinated interaction between a 1D finite-difference mathematical model and an automated size optimization process. A structural analysis of the circular plate supporting the bayonets was performed through the ANSYS 11 solver. The proposed steam cycles, 40 bar with superheating, 80 bar with live steam re-heating and 80 bar with double-superheating, show efficiency values of respectively 34%, 40% and 41%. A performance comparison with other cycles proposed in literature is provided. This solution is expected to provide significant safety advantages, for the secondary fluid low pressure and the gaseous flow in the heat exchangers, still keeping satisfactory efficiency values. (C) 2014 Elsevier Ltd. All rights reserved.