of less than 0 5 u03bcm can be effectively retained additionally or alternatively the venturi scrubber 12 may also be followed by preferably double gravity type drop separation with drop recirculation the depressurization and activity retention system 4 of the nuclear plant 1 is designed for particularly reliable activity retention and in particular for a degree of separation of the washing device of even comparatively fine grained aerosols with a particle size of less than 0 5 u03bcm of 98 or above for this purpose the venturi scrubber 12 and the throttle device 24 are deliberately coordinated with one another in terms of their dimensioning this is based on the design aim that in a response situation the depressurization gas stream flows through the venturi scrubber 12 at a particularly high flow velocity of more than 150 m s in particular of more than 200 m s to be precise as became apparent with such high flow velocities a virtually abrupt rise in the separation rate can be achieved and in particular even fine and the finest possible aerosol particles are bound in washing liquid droplets and are thus separated a suitable selection of in particular the flow cross sections ensures in this case that in virtually all the phases of an incident scenario such a high flow velocity prevails in the venturi scrubber 12 for this purpose on the one hand the throttle device.