The Morsleben repository for low-level and medium-level radioactive waste was established in the old Bartensleben salt and potash mine where several parts, e.g. the southern, eastern, and western part, were partially used for the disposal of waste. To analyse the integrity of the salt barrier in the southern, eastern and western parts in terms of stresses and dilatancy of the salt rock, numerous geomechanical finite-element calculations were performed taking into account the specific geological situation and mining geometry, as well as location-specific material parameters. The barrier integrity at each location was evaluated considering two criteria. The first criterion is related to dilatancy of rock salt: the integrity is guaranteed if rock stresses do not exceed the dilatancy boundary. The second criterion is related to fluid pressure: the integrity is guaranteed if the hydrostatic pressure of an assumed fluid column extending to the surface does not exceed the minimum principal stress at a certain location in the salt rock. The results of the investigations are the basis for evaluating the integrity of the salt barrier for an assumed time period of up to 10,000 years.
The ERA Morsleben (ERAM) geologic repository for radioactive waste was constructed in the former Bartensleben salt and potash mine consisting of several mining parts. The repository was used for the disposal of non heat-generating low radioactive and medium radioactive waste from 1972 to 1998. Especially the southern, the western, and the eastern parts located at the periphery of the mine were used for waste disposal. The emplacement zones are around 500m deep within the rock salt mass. To assess the geomechanical stability of these structures, as well as the integrity of the salt barrier, geotechnical safety analyses are necessary. These analyses are based on geological and engineering-geological studies of the site, laboratory tests and in-situ measurements, and on geomechanical model calculations. Model calculations are the most important part of the geotechnical safety assessment and comprise the geomechanical modelling of the host rock to simulate as closely as possible the conditions of the site and the behaviour of the rock, e.g. geology, repository or mine geometry, initial rock stress, as well as constitutive models and parameters.
