Coolant recirculation pump drawing in from a sump for the primary coolant loop of liquid-metal cooled nuclear reactors

The proposal relates to the improvement of a coolant recirculation pump drawing in from a sump for the primary coolant loop of a liquid-metal (e.g. Na) cooled nuclear reactor. The pump sump divided into upper and lower chambers by means of a partition has a throttled connection between pump outlet and upper chamber, which connection serves for maintenance of a predetermined liquid level in the upper chamber and makes it possible to maintain the top gas pressure in the sump at a level substantially identical with the top gas presssure in the reactor vessel. Various designs of the throttled connection are provided, including the feature that the throttled connection has a variable throttle opening. (HR)