Evaluation of Olkiluoto Hydrogeochemical Data in 3-D - with a Proceeding of Recent Geochemical Interpretation Results

Ari Luukkonen, Petteri Pitkänen, Sami Partamies

    Research output: Book/ReportReport

    Abstract

    Posiva Oy excavates in the Olkiluoto bedrock an underground facility (ONKALO). The characterisation program aims to develop techniques and new data for the evaluation of the planned repository site, and to contribute overall knowledge of the bedrock surrounding the future repository.

    The hydrogeochemical characteristics of the Olkiluoto study volume, both before excavations and during the years of ONKALO function, are among the important factors to be considered while assessing the safety of the site. Also the general consistency between hydrogeochemistry and hydrogeology is required. Moreover, the consistency is required with other disciplines as well (lithological, structural, mechanical). As the amount of data constantly increases within every discipline, the 3-D visualisation methods are becoming more and more important.

    The present 3-D visualisation method is based on the inverse geochemical calculations that are done for every qualified groundwater sample, and on the general geochemical expertise that has been gathered during the years of Olkiluoto studies. The present study introduces also a set of recent inverse interpretations that are utilised in the visualisations. Despite the continuous samplings expert judgement based compilations of data are inevitable since the study volume is huge compared to the amount of samples used to describe it. Sampling interpretations are classified according to their characteristics (geochemical and locational) to different groundwater flow areas. Information of these areas are condensed into a set of area characteristic distributions called primary "data" centroids. These primary centroids are assigned on the Olkiluoto map on the topographical and locational grounds. The condensed primary data is distributed into the Olkiluoto volume with mathematical regression calculations. The manipulation results continuous geochemical distributions in 3-D that are visualised by superimposing the distributions onto a fracture zone model.

    The 3-D visualisation method is independent of the fracture zone model. The 3-D geochemistry interpreted separately can be superimposed always onto an updated version of fracture zone model. The method is designed so that local distribution modifications can be done easily to the 3-D distributions. This feature is likely needed as geochemical data begin to gather from the disturbed site. Individual interpreted 3-D distributions can be saved and documented into separate directories. This gives the possibility to monitor and archive time-dependent changes within the studied 3-D volume.

    The 3-D visualisation method is independent from the modelling results of the other geological disciplines. The finding consistency among the disciplines means compromises within and between the disciplines.
    Original languageEnglish
    PublisherPosiva
    Number of pages71
    Publication statusPublished - 2005
    MoE publication typeD4 Published development or research report or study

    Publication series

    SeriesPosiva Working Report
    Number2005-72

    Keywords

    • 3-D visualisation
    • inverse calculation
    • groundwater
    • hydrogeochemistry
    • Olkiluoto

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