The safety assessment of radioactive waste repositories in salt formations requires geomechanical model calculations to analyze the stability of the repository mine and to predict the long-term integrity of the rock salt barrier. Important steps of this analysis are the geological exploration and modeling, the definition of material models and determination of related parameters, the geomechanical and numerical modeling as well as the specification of appropriate criteria to evaluate the numerical results. Two stress-based criteria are considered for rock salt: The dilatancy criterion and the frac criterion. As an example, the geomechanical integrity of the salt barrier in the southern part of the Morsleben repository, Germany, is investigated. Dilatant zones in the rock salt only occur directly around the rooms of the repository; sufficient areas of the salt barrier show no dilatancy even for long time periods. If backfilling of the repository rooms is taken into account, the frac criterion is satisfied too.