In situ resin impregnation for investigating radionuclide retardation in fractured repository host rocks

Due to current uncertainties in transport pathway (and pore space) characterisation, there has been a tendency to play down the potential role of the geosphere as a safety barrier in repository performance assessment. In an attempt to reduce these uncertainties, Nagra (National Cooperative for the Disposal of Radioactive Waste) and PNC (Power Reactor and Nuclear Fuel Development Corporation) have been carrying out a long-term programme of in situ experiments aimed at providing a more precise data base on transport pathways and sites of radionuclide retardation. Here, two experiments within this programme will be discussed to illustrate the use of in situ resin impregnation to better define in situ transport pathways and retardation sites. Details of the development work will be given along with information on the resin formulation. Finally, some examples of the completed work will be presented.