(EN) Disclosed is a gas and steam turbine (1) with a waste steam generator (4) which, seen from the flue gas, is located upstream from the gas turbine. The heated surfaces of the waste steam generator are connected to the steam-water circuit (20) of a steam turbine (21), the gas turbine being submitted to a reliable cooling process under various operating conditions. In order to refrigerate the gas turbine (6) coolant, the inventive system comprises a heat exchanger (74) which is connected, on the secondary side, in the water-steam circuit (76) linked as a locking element to the water-steam circuit (20) of the gas turbine (21).