[en] The closure device for caverns or penetrations equipped with liners in prestressed concrete pressure vessels consists of two closure parts functioning separately. They constitute a sealing lid and a support lid. Both lids are held by clamping devices anchored in the support lid made of concrete. The sealing lid, which is equipped with a flange, rests on the support lid under the impact of the internal pressure. A compensating seal may be installed between the flange and the liner to compensate for relative movements between the liner and the flange. The support lid proper is tightly connected to the liner by means of a welded lip joint. Moreover, parallel joints may be installed along the flange between which leak tests can be carried out. The sealing lid is double walled and the space in between the two walls is equipped with pressure equalization systems. (GL)