Recovering the Effects of Subgrid Heterogeneity in Simulations of Radionuclide Transport Through Fractured Media

Thomas Williams, Jordi Sanglas, Paolo Trinchero, Guanqun Gai, Scott L. Painter, Jan Olof Selroos

Research output: Contribution to journalArticlepeer-review

Abstract

Groundwater flow and contaminant transport through fractured media can be simulated using Discrete Fracture Network (DFN) models which provide a natural description of structural heterogeneity. However, this approach is computationally expensive, with the large number of intersecting fractures necessitated by many real-world applications requiring modeling simplifications to be made for calculations to be tractable. Upscaling methods commonly used for this purpose can result in some loss of local-scale variability in the groundwater flow velocity field, resulting in underestimation of particle travel times, transport resistance and retention in transport calculations. In this paper, a transport downscaling algorithm to recover the transport effects of heterogeneity is tested on a synthetic Brittle Fault Zone model, motivated by the problem of large safety assessment calculations for geological repositories of spent nuclear fuel. We show that the variability in the local-scale velocity field which is lost by upscaling can be recovered by sampling from a library of DFN transport paths, accurately reproducing DFN transport statistic distributions and radionuclide breakthrough curves in an upscaled model.

Original languageEnglish
Article number586247
JournalFrontiers in Earth Science
Volume8
DOIs
StatePublished - Feb 2 2021

Funding

This work was funded by Svensk Kärnbränslehantering AB (SKB).

Keywords

  • discrete fracture network
  • downscaling
  • groundwater modeling
  • radionuclide transport
  • upscaling

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