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Recovering the effects of subgrid heterogeneity in simulations of radionuclide transport through fractured media

Journal Article · · Frontiers in Earth Science
 [1];  [2];  [2];  [1];  [3];  [4]
  1. Jacobs, Didcot (United Kingdom). Harwell Campus
  2. AMPHOS 21 Consulting S.L., Barcelona (Spain)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Svensk Kärnbränslehantering AB (SKB), Solna (Sweden)

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.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1765490
Journal Information:
Frontiers in Earth Science, Journal Name: Frontiers in Earth Science Vol. 8; ISSN 2296-6463
Publisher:
Frontiers Research FoundationCopyright Statement
Country of Publication:
United States
Language:
English