CALIBRE and CRYSTAL: Near-field and geosphere models for Project-90

A new near-field model (CALIBRE) and a fractured geosphere model (CRYSTAL) have been developed in support of the Swedish Nuclear Power Inspectorate's Project-90 safety assessment of a reference repository for spent nuclear fuel. CALIBRE calculates in two dimensions the twin problems of oxidant and radionuclide migration through a bentonite buffer and fractured host rock, with redox front formation and precipitation of nuclides at the redox front. The output from CALIBRE can be input directly to the CRYSTAL code, which is a fast, one-dimensional contaminant transport model of a fractured rock geosphere. This paper describes the main features of the models and illustrates how certain processes can have a significant impact on the flux of radionuclides emerging from the near field to the geosphere, and from the geosphere to the biosphere