Technical Report NTB 84-40

Radionuclide Sorption Database for Swiss Safety Assessment

In this report recommended sorption data for use in transport models for a Swiss High-Level Waste repository are presented. The models used in "Project Gewaehr 1985" assume linear sorption isotherms and require elemental partition coefficient (Kd) data. On the basis of a literature search "realistic" Kd data for 22 elements have been selected for weathered crystalline rock and sediments in contact with a reducing groundwater and also sediments with a less reducing groundwater. In an appendix sorption data for 28 elements on bentonite backfill are given. These data are supplemented with "conservative" estimates taken to represent minimum reasonable values. Available data are discussed for each element clearly exhibiting (i) the large gaps in knowledge, (ii) their unbalanced distribution between different elements and, hence, (iii) the need for further experiments in the laboratory, the field and analogue studies. An overview of the theoretical concepts of sorption, experimental methodology and data interpretation is given in order to put the values into context. General problem areas are identified.