[en] A preliminary design was completed for a steam generator which is applicable to a four loop LMFBR plant of 1000 MWe gross output employing dry and saturated steam conditions. Two steam generators of 364 MWt thermal capacity would be in each loop. The steam generator is a straight, duplex tube design with a shell bellows for thermal expansion and a single tubesheet with an integral leak detection system. The report outlines a proposed series of development tasks to provide additional design data for the duplex tube and to demonstrate the steam generator design with test modules. The design can be adapted readily as either the evaporator or the superheater for a superheated steam cycle with temperatures up to at least 430⁰C (800⁰F), which is below the creep range for the 2 1/4 Cr-1 Mo material