In apparatus for emergency cooling of a steam generator unit (1) of a nuclear power plant wherein blow-off steam is condensed in a closed circuit and the resulting condensate is returned to the steam generator as feed water, the steam is passed through a blow-off pipe (11) into a closed vessel (14) comprising a water space (12) and a gas space (13). A bundle of heat exchanger tubes (15) extends through the vessel (14). An end part of the blow-off pipe (11) extending into the water space (12) is angularly bent and is designed as a steam distributor nozzle (18) which is arranged opposite to the bundle of heat exchanger tubes (15). The thermo-syphon effect and hence the efficiency of the apparatus are increased with this arrangement so that the amount of steam blown off can be taken up in a relatively small vessel.