The planning of critical infrastructures in developed countries is a challenging task for investors accompanied by a significant amount of project risks. The development of the seismic design basis of critical infrastructures is a main contributor to these project risks and accompanied by a large amount of scientific, technical and mainly political uncertainties. A procedure is proposed how to structure the decision making process with respect to the seismic design basis from the perspective of the designer of a critical infrastructure. The procedure assures a robust and time-invariant decision-making, leading to economically acceptable design solutions and plant designs characterized by a low contribution of seismic hazard to the plant operational risk. The application of the procedure is demonstrated for the design of a new fictive nuclear power plant located at the current site of the nuclear power plant Goesgen in Switzerland. The procedure can be applied in a similar way for any other type of short-lived critical infrastructure.