Synthesis of the workshop

Several past, current and planned field tracer experiments were described and discussed in the course of the workshop. They cover various potential repository host rocks from soft argillaceous media to hard, fractured crystalline basement; make use of a wide range of both sorbing and non-sorbing (conservative) tracers; and cover various types of geologic features at different spatial and temporal scales. The workshop provided a broad perspective on the advantages and limitations of field tracer experiments, and a set of conclusion and recommendations that will be useful when designing future tests. The main conclusions of the workshop are discussed in detail. Field tracer experiments should continue to form part of the research needed for performance-assessment modelling as they provide important technical information, help build confidence in performance-assessment models, and provide much, sometimes unexpected, supporting information and understanding of radionuclide-migration mechanisms. (author)