A new approach to account for fracture aperture variability when modeling solute transport in fracture networks

Larsson, Martin; Odén, Magnus; Niemi, Auli; Neretnieks, Ivars; Tsang, Chin‐Fu

doi:10.1002/wrcr.20130

Cited by 18 publications

(7 citation statements)

References 33 publications

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“…This can have a considerable impact on the retardation in the fracture. Larsson et al [2013] showed how sFWS can be included in DFN modeling. Water Resources Research…”

Section: Mathematical and Numerical Approaches To Modeling Of Flow Anmentioning

confidence: 99%

Hydrologic issues associated with nuclear waste repositories

2015

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Significant progress in hydrology, especially in subsurface flow and solute transport, has been made over the last 35 years because of sustained interest in underground nuclear waste repositories. The present paper provides an overview of the key hydrologic issues involved, and to highlight advances in their understanding and treatment because of these efforts. The focus is not on the development of radioactive waste repositories and their safety assessment, but instead on the advances in hydrologic science that have emerged from such studies. Work and results associated with three rock types, which are being considered to host the repositories, are reviewed, with a different emphasis for each rock type. The first rock type is fractured crystalline rock, for which the discussion will be mainly on flow and transport in saturated fractured rock. The second rock type is unsaturated tuff, for which the emphasis will be on flow from the shallow subsurface through the unsaturated zone to the repository. The third rock type is clay-rich formations, whose permeability is very low in an undisturbed state. In this case, the emphasis will be on hydrologic issues that arise from mechanical and thermal disturbances; i.e., on the relevant coupled thermo-hydromechanical processes. The extensive research results, especially those from multiyear large-scale underground research laboratory investigations, represent a rich body of information and data that can form the basis for further development in the related areas of hydrologic research. General IntroductionSignificant progress in hydrology, especially in subsurface flow and solute transport, has been made over the last 35 years because of sustained interest in the performance assessment of proposed underground nuclear waste repositories. The present paper attempts to provide an overview of the key hydrologic issues involved and to highlight the advances in their understanding and treatment because of these efforts. This paper is not focused on the development of high-level nuclear waste repositories and their safety assessment; it focuses instead on the advances in hydrologic science which have emerged from such studies. These advances may find applications in other hydrology-related problems of current importance at the national and international levels, such as environmental contamination remediation, carbon dioxide geosequestration, and natural gas production through fracking.In the next section, we present, in a general way, the context for the hydrologic framework related to performance and safety assessment of underground nuclear waste repositories that are proposed to be constructed in three particular rock formations-crystalline rock, unsaturated tuffs, and clays. Then, we discuss some particularly challenging factors concerning the research common to these three formations. This discussion will be followed by three sections devoted to each of these three rock types, respectively, to present a review of hydrologic research in these areas.

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“…This can have a considerable impact on the retardation in the fracture. Larsson et al [2013] showed how sFWS can be included in DFN modeling. Water Resources Research…”

Section: Mathematical and Numerical Approaches To Modeling Of Flow Anmentioning

confidence: 99%

Hydrologic issues associated with nuclear waste repositories

2015

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“…Thus, aperture variation over each fracture is not accounted for. This aperture variation is what gives rise to flow channeling effect (Larsson et al., 2013). In the CNM, the channeling effect is accounted for directly by channels determined through the calibration process.…”

Section: Predictions Of Long‐term Tracer Transport Based On Calibrate...mentioning

confidence: 99%

Channel Network Modeling of Flow and Transport in Fractured Rock at the Äspö HRL: Data‐Worth Analysis for Model Development, Calibration and Prediction

Dessirier

Sharma

Pedersen

et al. 2023

Water Resources Research

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Performance assessment of nuclear waste disposal in deep crystalline bedrock demands a thorough understanding of the related flow and transport processes. Uncertainties may arise both from the selection of the conceptual model as well as the estimation of the related model parameters. Discrete fracture network (DFN) models are widely used for such modeling while channel network models (CNM) provide an alternative representation, the latter focusing on the fact that flow and transport in deep fractured media often are dominated by a small number of long preferential flow paths. This study applies the principle of channel networks, implemented in the Pychan3d simulator, to analyze the hydraulic and tracer transport behavior in a 450‐m‐deep fractured granite system at the Äspö Hard Rock Laboratory in Sweden, where extensive site characterization data, including hydraulic and tracer test data are available. Semi‐automated calibration of channel conductances to field characterization data (flow rates, drawdowns, and tracer recoveries) is performed using PEST algorithm. It was observed that an optimal CNM connectivity map for channel conductance calibration can only be developed by jointly fitting flow rates, drawdowns and tracer mass recovery values. Results from data‐calibrated CNM when compared to a corresponding calibrated DFN model shows that the CNM calibrates and adapts better than a DFN model with uniform fracture surfaces. This comparative study shows the differences and uncertainties between two models as well as examines the implications of using them for long term model predictions.

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“…More recent improvements in DF model equations (Shahkarami et al, 2019) include the non-equilibrium pollutant transport in fractures by coupling the kinetic equation of the pollutant mass adsorption-desorption and diffusion into the rock matrix or in the lateral dead-ends of fractures, to the advection-dispersion transport equation. Furthermore, for the reactive pollutant transport in fractures, a simple and efficient method was presented by Larsson et al (2013) to account for the effects of the specific flow-wetted surface (sFWS) during pollutant transport with reactions. This sFWS is the fraction of the fracture wall contact area where pollutant adsorption occurs during the transport in fractures of DFN.…”

Section: Pollutant Transport Into a Single Fracture Of The Df Modelmentioning

confidence: 99%

“…Furthermore, for the reactive pollutant transport in fractures, a simple and efficient method was presented by Larsson et al. (2013) to account for the effects of the specific flow‐wetted surface (sFWS) during pollutant transport with reactions. This sFWS is the fraction of the fracture wall contact area where pollutant adsorption occurs during the transport in fractures of DFN.…”

Section: Implementation Of New Flow and Transport Equationsmentioning

confidence: 99%

Hydrogeological Models of Water Flow and Pollutant Transport in Karstic and Fractured Reservoirs

Masciopinto¹,

Passarella²,

Caputo³

et al. 2021

Water Resources Research

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Water flow and solute transport models in fractured aquifers and rock outcrops have been extensively studied during the last 40 years. Many of these studies have focused on specific bedrock formations, such as the Stripa mine and Äspö Island, in Sweden, or the Yucca Mountain of Nevada, USA (Doughty, 1999), where radionuclide repositories have the potential to release radioactive pollutants into groundwater and/or surface water and pose a threat to human health. In particular, several studies concerning flow and transport models in fractured media have been published between 1980 and 2000(Moreno & Neretnieks, 1993Tsang et al., 2015). These studies mostly focused on fractured formations with few or discrete fractures (DF),

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A new approach to account for fracture aperture variability when modeling solute transport in fracture networks

Cited by 18 publications

References 33 publications

Hydrologic issues associated with nuclear waste repositories

Hydrologic issues associated with nuclear waste repositories

Channel Network Modeling of Flow and Transport in Fractured Rock at the Äspö HRL: Data‐Worth Analysis for Model Development, Calibration and Prediction

Hydrogeological Models of Water Flow and Pollutant Transport in Karstic and Fractured Reservoirs

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