[en] The DWTSG concept is proposed as a new liquid metal reactor concept to avoid sodium-water reaction incidents in the SG. This present paper attempts to assess thermal characteristics of DWTSG in the this alternate concepts. The concept provides double barrier between the sodium and the steam. This will result in improved reliability of SG compared to the conventional steam generator design using single wall tubes. The gap between the inner and outer tubes affects the heat transfer from sodium to steam. To estimate heat transfer performance of the concept, the required heat transfer area was calculated, and compared with MONJU SG. In the case of eliminating of IHTS the required heat transfer area for DWTSG is equally mated to that of MONJU design