This report presents modeling work for predictions and evaluation of the BS2B tracer experiment of the TRUE Block Scale Continuation project. Tracer tests were performed along two flow paths using a variety of different sorbing tracers. Path lengths were over 20 m for both flow paths. In the flow path I the injection location was in the same fault type feature as extraction location (Structure #19). In the flow path II the injection was performed in the separate non-fault type background feature (BG1). The connection from BG1 to #19 is not known deterministically. The Euclidean distance from injection location to extraction location is in this case about 20 m, but the actual path length is probably longer because BG1 and #19 are subparallel. A blind prediction of the tracer test outcome was performed prior to the evaluation of the experiment. The prediction was based on the given micro-structural model of the immobile pore space along the flow paths, results of the non-sorbing tracer tests and dilution measurements of the flow rates at the injection locations. Predictive modelling showed too much retention for sorbing tracers. Evaluation of the tracer tests indicates that effective immobile zone retention properties are stronger along the flow path I, which goes along the associated fault type fracture. Effective immobile zone retention properties along the flow path II (injection at the non-fault fracture) seems to be dominated by the properties of non-fault background fractures. An interesting observation of the evaluation has been that a model of single unlimited immobile zone with sorption and matrix diffusion works very well for all breakthrough curves. Evaluation has showed that very distinct layers of different materials at a centimetre scale (thickness of the material layer) should manifest themselves in the breakthrough curves of the non-sorbing tracers at the experimental time scale of BS2B.
|Place of Publication||Stockholm|
|Publisher||Svensk Kärnbränslehantering AB (SKB)|
|Number of pages||69|
|Publication status||Published - 2005|
|MoE publication type||D4 Published development or research report or study|
|Series||SKB International Progress Report|