DOPAS aims to improve the adequacy and consistency regarding industrial feasibility of plugs and seals, the measurement of their characteristics, the control of their behavior over time in repository conditions and also their hydraulic performance acceptable with respect to the safety objectives.This DOPAS project addresses the design basis, reference designs and strategies to demonstrate the compliance of the reference designs to the design basis, for plugs and seals in geological disposal facilities. The project focuses on shaft seals for salt rock (German repository concept), tunnel plugs for clay rock (French and Swiss repository concepts), and tunnel plugs for crystalline rock (Czech, Finnish and Swedish repository concepts). Five different demonstration experiments are part of the project and will take place in Sweden, France, Finland, Czech Republic and Germany. They are in different state-of-development. The Swedish demonstrator will be constructed prior to start of the DOPAS project and will basically provide experience on demonstration of compliance of reference design to the design basis. German demonstrator will be installed after the DOPAS project and will focus on demonstration of suitability by performance assessment. The French, Finnish, Swedish,German and the Czech experiments will address developments in all phases of design basis, reference designs and strategies to demonstrate compliance of reference designs to design basis. The studied concepts will be developed in the DOPAS's five thematic scientific/technological work packages, which each integrate the results of the individual experiments.The DOPAS project is derived from the IGD-TP's Strategic Research Agenda that points out the topic of “plug and seals” as a first priority issue for joint European RTD projects.