[en] Within the German research program on PCRV for light water reactors, sponsored by the Bundesminister fuer Forschung und Technologie, theoretical and parametric studies were done at the Institut fuer Konstruktiven Ingenieurbau, Ruhr-Universitaet Bochum. Part of this work was the development of a method for calculating ultimate load behaviour of PCRV, as described in SMiRT-3 paper H 4/6. In order to check the quality of the method a number of ultimate load calculations for vessels and vessel components with various shapes has been carried out. One is exemplary presented in this paper. It concerns a model of a removable concrete top closure, which has been developed by Fried. Krupp GmbH within the same research program. Two identical models were tested in order to study ultimate load behaviour. The shape of such a slab is characterized by a close fitting to the dome generated under internal pressure in the concrete continuum. No remarkable cracking could be observed during testing the models up to pressures of 450 kg/cm² and 550 kg/cm², respectively. The tests were ceased without reaching failure. (Auth.)