Radionuclide retardation in crystalline rock fractures

Transport and retardation of slightly sorbing sodium was studied in Syyry area SY-KR7 mica gneiss and in altered porous tonalite. Experiments were performed using dynamic fracture and crushed rock column methods and the static batch method. Flow conditions in the column were determined using tritiated water and chloride as non-sorbing tracers. 14C-PMMA method was used to study the pore structure of matrices and the surface areas were determined by B.E.T. method. Sodium was retarded strongly in altered tonalite owing to homogeneous porous matrix structure and the composition of alteration minerals. An agreement between retardation values in batch and crushed rock column experiments as well as in fracture column experiments was good