Floating roof tanks for liquid, in particular to storage tanks used in the nuclear power industry

A floating roof tank for liquids, the tank comprising a cylindrical wall, a floating roof surrounded by said cylindrical wall, a flexible membrane connecting said floating roof to said wall in a watertight manner, said membrane defining together with the wall of the tank a space which is suitable for receiving a counter-pressure liquid, and the tank including the improvement whereby it is fitted with means for emptying the volume of counter-pressure liquid when the roof is in its high position, said emptying means being disposed in the upper portion of the tank in such a manner that the flexible membrane serves to expel the counter-pressure liquid under the effect of the pressure exerted on the membrane by the liquid contained in the tank, said emptying means including an emptying orifice passing through the wall of the tank in the upper portion thereof, said orifice being connected to a conventional emptying duct outside said wall, and said emptying means further including means for preventing said emptying orifice from being closed by the flexible membrane, such that a complete emptying of the counter-pressure liquid can be achieved.