Performance assessments for the disposal of low-level wastes into an iron-ore formation

Radioactive wastes producing negligible heat production are planned to be disposed of into a deep iron ore formation in Lower Saxony. For this repository at the Konrad site a performance assessment has been carried out as part of the licensing procedure. As a first part of the exercise the flow of groundwater has been modelled and scenarios for nuclide migration have been established. The assumptions for the groundwater modelling and the results from the calculations are explained and the resulting scenarios are described. In the second part the release of radionuclides from the near field has been investigated. The release from near field is influenced by the degradation of the waste forms, the retention of radionuclides by sorption and precipitation and the groundwater flow through the repository system. Finally in part three of the exercise the migration of radionuclides through the geosphere is considered. The simplified model used for migration calculations has been extracted from the groundwater modelling. For migration modelling, sorption and dispersion phenomena, and dilution by fresh water are taken into account. The results obtained from the groundwater modelling, the release calculations, and the migration modelling are presented. The relevance of the considered phenomena are discussed