SAFETY CONCEPT AND CRITERIA FOR HAZARDOUS-WASTE SITES

The problem of waste disposal in Germany has been solved by using a co mbination of above-ground and underground disposal. Site selection cri teria and precise criteria for the performance assessment of various t ypes of waste disposal are available. In view of long-term safety of d isposal, it is necessary to include geological and hydrogeological vie wpoints in addition to purely engineering viewpoints. In particular, t he geotechnical site-specific safety assessment is described, as defin ed by the government in ''Technical Regulations on Wastes'' (TA-Abfall ) in the section ''Underground Disposal''. This safety assessment must cover the entire system comprising waste, cavern/mine and surrounding rock. For this purpose geo-mechanical models have to be developed. Ac cording to the multi-barrier principle, the geological setting must be able to contribute significantly to isolation of the waste over longe r periods. The assessment of the integrity of the geological barrier c an only be performed by making calculations with validated geomechanic al models. Various engineering geological data are required for the se lection of a site, for the design and construction of a repository, an d for a safety analysis for the post-operational phase. These data can only be attained by the execution of a comprehensive site-specific ge omechanical exploration and investigation program. The planning and de sign of an underground repository in rock salt layers are described, a s an example for the various steps of this type of safety assessment.