The objective of the DOPAS international project is to design a sealing-plug system for deep geological repository (DGR) use, to provide detailed plans for the design of such plugs, to test the characteristics of the materials to be used and the construction technology and to install four experimental in situ plugs. The Czech experimental pressure and sealing-plug (EPSP) experiment is being conducted in a rock environment consisting of granitoids at the Josef Regional Underground Research Centre. The concept of the experiment is based primarily on the use of materials and technology available in the Czech Republic and the principal aim is to demonstrate the technical viability and functioning of a pressure-resistant plug located in a future DGR. The completion of the EPSP experiment will contribute towards both the demonstration of how sealing-plug systems behave under real underground conditions and the long-term safety of a future DGR in the Czech Republic.