Analysis of the migration of instantaneously injected cesium in artificial fractures of Lac du Bonnet granite, Manitoba, Canada

Fujikawa, Yoko; Fukui, Masami; Drew, Doug J.; Vandergraaf, T. T.

doi:10.1016/0169-7722(93)90025-n

Cited by 8 publications

(5 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Diffusion coefficients have been determined in many laboratory experiments using various tracers and rocks [ Hill , 1984; Bradbury and Green , 1985, 1986; Moreno et al , 1985; Skagius and Neretnieks , 1986; Fujikawa et al , 1993]. Others have performed field experiments toward the same aim [ Black and Kipp , 1983; Moench , 1995; Jardine et al , 1999].…”

Section: Introductionmentioning

confidence: 99%

“…Concentration changes inside a rock due to matrix diffusion from fractures have been typically estimated by solving the diffusion equation, following the measurement of breakthrough curves at the fracture outlet [e.g., Foster , 1975; Neretnieks , 1980; Grisak and Pickens , 1980, 1981; Tang et al , 1981; Fujikawa et al , 1993; Parker et al , 1994]. Concentration distributions inside a rock matrix have been directly measured in only a few experiments.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Chemical diffusion between a fracture and the surrounding matrix: Measurement by computed tomography and modeling

Polak

Grader

Wallach

et al. 2003

Water Resources Research

View full text Add to dashboard Cite

[1] A medical-based X-ray CT scanner was used to monitor the diffusion of NaI into the matrix of a 20-cm-long, 5-cm diameter fractured chalk core. The core was retrieved from a core hole at a depth of 18.3 m and was artificially fractured along its axis using a Brazilian-like test. The NaI solution flowed continuously along the vertically oriented fracture and the transient lateral concentration distribution within the matrix at different cross sections along the core was monitored by two-dimensional 2-mm-thick slices through the sample and an in-plan pixel resolution of about 0.25 mm. The lateral concentration distribution within the matrix was characterized by a sharp decrease at a thin matrix layer adjacent to the fracture/matrix interface followed by diffusion-type concentration distribution elsewhere. This concentration variation suggests that a thin transition layer exists along the fracture/matrix interface where the diffusion coefficient is higher than that of the bulk matrix. The higher diffusion coefficient of the transition layer is possibly related to minifissures that develop when fractures are formed. After 6 days of tracer injection into the fracture inlet, distilled water was injected for 11 days, forming a reverse concentration gradient and back diffusion. A mathematical model that assumes diffusion within the matrix and a linear concentration variation through the transition layer from its value in the fracture to its time-dependent value at the transition layer/matrix interface was developed. Very good agreement was obtained between the predicted and measured concentrations during both the diffusion and back diffusion phases. Application of the model to a field site in the Negev desert, Israel, suggested that the rock matrix that had been subjected to 20 year of contaminant diffusion would require more than 200 years before it would stop releasing contaminants into the intersecting fractures (a parabolic process). According to these calculations, remediation efforts based on clean water injection into the fractures are not feasible.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemical diffusion between a fracture and the surrounding matrix: Measurement by computed tomography and modeling

Polak

Grader

Wallach

et al. 2003

Water Resources Research

View full text Add to dashboard Cite

show abstract

“…1,2 There is great interest in measuring the sorption of radionuclides in flowing fractures, and careful laboratory tests have been performed. [3][4][5] For practical reasons, most lab experiments are run at higher Pe than field conditions, with relatively short flow paths. In rough-walled fractures, it is very difficult to distinguish true sorption from the enhanced dispersion that comes with stagnant zones, which suggests that one should use more regular geometries for lab tests, such as prismatic channels machined into solid rock samples.…”

Section: Introductionmentioning

confidence: 99%

Accuracy and Computational Efficiency in 3D Dispersion via Lattice-Boltzmann: Models for Dispersion in Rough Fractures and Double-Diffusive Fingering

Stockman

Glass

Cooper

et al. 1998

Int. J. Mod. Phys. C

View full text Add to dashboard Cite

In the presence of buoyancy, multiple diffusion coefficients, and porous media, the dispersion of solutes can be remarkably complex. The lattice-Boltzmann (LB) method is ideal for modeling dispersion in flow through complex geometries; yet, LB models of solute fingers or slugs can suffer from peculiar numerical conditions (e.g., denormal generation) that degrade computational performance by factors of 6 or more. Simple code optimizations recover performance and yield simulation rates up to ~3 million site updates per second on inexpensive, single-CPU systems. Two examples illustrate limits of the methods: (1) Dispersion of solute in a thin duct is often approximated with dispersion between infinite parallel plates. However, Doshi, Daiya and Gill (DDG) showed that for a smooth-walled duct, this approximation is in error by a factor of ~8. But in the presence of wall roughness (found in all real fractures), the DDG phenomenon can be diminished. (2) Double-diffusive convection drives "salt-fingering", a process for mixing of fresh-cold and warm-salty waters in many coastal regions. Fingering experiments are typically performed in Hele-Shaw cells, and can be modeled with the 2D (pseudo-3D) LB method with velocity-proportional drag forces. However, the 2D models cannot capture Taylor–Aris dispersion from the cell walls. We compare 2D and true 3D fingering models against observations from laboratory experiments.

show abstract

“…In this case, Taylor dispersion is the only physical mechanism that spreads mass along the fracture. Dispersion of conservative and ideally sorbing solutes in a constant-aperture fracture has been described using analytical techniques [Kessler and Hunt, 1994], numerical simulations [Wels, 1995], and migration experiments [Vandergraaf et al, 1988;Fujikawa et al, 1993]. Vandergraaf et al [1988] noted that for a continuous injection of tracer into a sawed fracture in granite, dispersion of cesium was considerably greater than that for a conservative tracer.…”

Section: Introductionmentioning

confidence: 99%

“…A quantitative analysis of the breakthrough curves was not presented. Fujikawa et al [1993] performed migration experiments similar to those of Vandergraaf et al [1988], using pulse injections of cesium. They noted a strong dependence of the breakthrough curves, in particular peak height and tailing, on the fluid velocity in the fracture.…”

Section: Introductionmentioning

confidence: 99%

Influence of Specific Surface Area on Transport of Sorbing Solutes in Fractures: An Experimental Analysis

Wels¹,

Smith²,

Vandergraaf³

1996

Water Resources Research

View full text Add to dashboard Cite

Experimental evidence is presented on the influence of specific surface area on the transport of the sorbing tracer strontium in fractures with uniform, but differing aperture. Specific surface area is defined as the ratio of the fracture surface area to the volume of mobile water in the fracture. Static sorption experiments on granite coupons suggest hysteresis in the sorption process, showing higher surface distribution coefficients for desorption than for sorption. Strontium was subject to significantly greater dispersion than the nonreactive tracer tritium. This enhanced dispersion is believed to be the result of chemical heterogeneity at the mineral grain scale, hysteresis in sorption, and limited transverse mixing across the fracture aperture. The influence of fracture aperture on retardation is much greater than predicted by the commonly used definition of the surface retardation factor. Strontium retardation was approximately an order of magnitude greater in a smaller‐aperture fracture (450 µm, Ra ∼ 45) than in a large‐aperture fracture (780 µm, Ra ∼ 3.5). We hypothesize that hysteresis in sorption, in conjunction with limited transverse mixing across the aperture, caused the apparent increase in sorption strength (Ka) with a decrease in fracture aperture.

show abstract

Analysis of the migration of instantaneously injected cesium in artificial fractures of Lac du Bonnet granite, Manitoba, Canada

Cited by 8 publications

References 25 publications

Chemical diffusion between a fracture and the surrounding matrix: Measurement by computed tomography and modeling

Chemical diffusion between a fracture and the surrounding matrix: Measurement by computed tomography and modeling

Accuracy and Computational Efficiency in 3D Dispersion via Lattice-Boltzmann: Models for Dispersion in Rough Fractures and Double-Diffusive Fingering

Influence of Specific Surface Area on Transport of Sorbing Solutes in Fractures: An Experimental Analysis

Contact Info

Product

Resources

About