Testing repository safety assessment models for deep geological disposal using legacy contaminated sites.

An important property of locations selected to host deep geological repositories for higher level radioactive wastes is their capacity to retard the movement of any radionuclides released from engineered barriers. Site characterization cannot measure this characteristic directly and hence models form the essential link between field observations and supporting laboratory rock/water/radionuclide interaction studies. However, residual uncertainties always remain, associated with the complexity of radionuclide interactions in natural environments and the extrapolations in time and space that are included in safety assessments. An under-used resource that could help to strengthen the safety cases that utilize such information, is the knowledge base available from anthropogenically contaminated sites. These have the potential to combine relevant geological settings with the radionuclides of interest and timescales in the order of decades allow typically slow processes to be better quantified. This paper provides an overview of the range of options available, critically reviews some relevant examples where radionuclide migration models could be tested and outlines work that could facilitate utilization of this potential resource in order to strengthen the safety case for geological repositories.