[en] The arrangement is described of heat exchange tubes of the steam generator of a nuclear power plant with a sodium cooled fast reactor. The protective tube is anchored in the tube plate only at one end and the space between the protective tube and the separating tube is thus connected with the space of liquid metal in the steam generator. In case of the escape of water into the sodium the amount of sodium between the protective and the separating tube is so small that the heat load of the tubes is small and the reaction zone shifts along the tube which excludes the possibility of the burning up of the tube. The advancing water cools the tubes and the dimensions of the slot between the protective and the separating tubes restricts the quantity of penetrating water also in case of the failure of the separating tube in the full cross-section. (J.B.)