Steam generator with duplex heat exchange tubes

The invention claims a design of a steam generator for fast reactors. The advantage of the design is that it does not require additional expansion tanks for the steam generator and that the steam generator may be filled with indication liquid, e.g., sodium, after assembly work has been completed at the power plant. Another advantage is that in a vertical steam generator with duplex heat exchange tubes the configuration facilitates the detection of a failure of the walls of the duplex tubes. (J.P.)