One of the main issues, regarding the development of Generation IV nuclear power plants, is the safety. In order to design nuclear systems characterized by enhanced safety features, an innovative and passive system, aimed at decay heat removal, especially suitable for sodium cooled fast reactors, has been developed. The attention is here mainly focused on an innovative, passive, decay heat removal system, proposed for liquid metal cooled reactors and based on a radiation-based bayonet tube heat exchanger that allows to remove decay heat from the primary coolant. Heat transfer is mainly guaranteed by the radiation mechanism, since each bayonet tube is equipped with a vacuum gap required to better decouple primary and secondary coolants and to detect possible leakage. The secondary fluid flows within the bayonet tubes in natural circulation. The proposed heat exchanger presents important advantages from the safety point of view, including the good compatibility between primary and secondary coolants, the good heat transfer properties of secondary fluids and, above all, the possibility to detect immediately any leak from both primary and secondary side, thanks to a continue monitoring of the vacuum gap pressure. In this paper, several CFD analyses, aimed at analyzing different parameters’ influence on the heat transfer capability of the system, have been discussed.