Mass transfer in a salt repository

Pigford, T.H.

doi:10.2172/6381376

Cited by 6 publications

(2 citation statements)

References 8 publications

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“…A mathematical model was developed for the Deaf Smith Draft Environmental Assessment (Gupta et al, 1987), based purely upon curve-fitting a diffusion model to observed brine inflow (Pigford and Chambrè, 1985). This model was criticized for its lack of physical justification (Sherer, 1987, p. v & p. C.92).…”

Section: Historic Brine Flow Models Without Mechanical Effectsmentioning

confidence: 99%

Brine flow in heated geologic salt.

Kuhlman¹,

Malama²

2013

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This report is a summary of the physical processes, primary governing equations, solution approaches, and historic testing related to brine migration in geologic salt. Although most information presented in this report is not new, we synthesize a large amount of material scattered across dozens of laboratory reports, journal papers, conference proceedings, and textbooks.We present a mathematical description of the governing brine flow mechanisms in geologic salt. We outline the general coupled thermal, multi-phase hydrologic, and mechanical processes. We derive these processes' governing equations, which can be used to predict brine flow. These equations are valid under a wide variety of conditions applicable to radioactive waste disposal in rooms and boreholes excavated into geologic salt. 3We focus on the development of the governing equations with the intent to solve them analytically or in a simplified numerical manner, although we briefly summarize some available fully coupled three-dimensional numerical models and some historic modeling results. We non-dimensionalize the governing equations, and make some statements about importance of terms in the governing equations for physically plausible ranges of material property values.We summarize both in situ and laboratory brine migration testing in intact geologic salt, primarily focusing on tests performed under heated conditions relevant to high-level waste disposal. Supporting material is presented in appendices on relevant aspects of laboratory water content determination for bedded salt, the nature and evolution of the disturbed rock zone, and geologic salt permeability testing.In the final summary chapter, we provide a narrative description of the processes controlling both isothermal and heated brine inflow to excavations in geologic salt. Based upon our review, we recommend several potential in situ and laboratory tests, which could be conducted to increase understanding, parametrize numerical models, and confirm the importance of competing physical processes.4

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Section: Historic Brine Flow Models Without Mechanical Effectsmentioning

confidence: 99%

Brine flow in heated geologic salt.

Kuhlman¹,

Malama²

2013

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“…Although experiments and experience at potential salt sites indicate that salt may contain brine, the low porosity and permeability of jalt make ; * dill a good choice for geologic isolation. Here we summarize some analyses of near-field mass transfer in salt repositories [Pigford and Chambre 1985].…”

Section: Near-field Mass Transfer In a Salt Repositorymentioning

confidence: 99%

A review of near-field mass transfer in geologic disposal systems

Pigford¹,

Lee²

1990

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N*u4«ld Maw Trantfw 2.0 LOW-SOLUBILITY SPECIES The dissolution rate of waste solids in a geologic repository is a complex function of waste solid geometry, chemical reaction rate, exterior flow field, and chemical environment. Our analysis of dissolution rates is divided into those of low solubility and readily soluble. 2.1 Dissolution from Waste Into Porous Rock with a Solubility Boundary Condition We are concerned with the transfer of a diffusing species from a waste form into porous rock. The governing equation in the most general sense, without accounting for losses, is K-+ vVc = DV 3 c (2.1.1) at where c is the concentration of the species in ground water, v is the ground water velocity, D the diffusion or dispersion coefficient and A" is the species retardation coefficient. The solubility boundary cotidition is c = c, (2.1.2) on the surface of the waste form the concentration is that of the species solubility e, (Figure 2.1), and the other boundary condition is c=0, at infinity (2.1.3) and the initial condition c = 0, < = 0 (2.1.4) We shall be concerned with solving this set of governing equations in various forms throughout the remainder of this paper. 2.1.1 Steady-State Results 2.1.1.1 Diffusive The steady-state form of the equation for for mass transfer by molecular diffusion a low-solubility longlived species, assuming constant saturation concentration c, in the liquid at the waste surface and assuming that the waste solid is surrounded by porous rock, is /=^i (2.1.1.1.1) where / is the fractional dissolution rate of the species, t is the porosity of the rock, D is the diffusion coefficient in pore water, and M is the bulk density of the elemental species in the waste. B is a geometrical factor that can be calculated from the waste-form dimensions. For a spherical waste solid of radius R B=± (2.-1.1.1.2) For a prolate spheroid approximating a cylindrical waste form 3£ * = 6*log[coth(*,/2)]

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Analyses of mass transport in a nuclear waste repository in salt

Hwang¹,

Pigford²,

Lee³

1992

Water Resources Research

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Salt is the proposed host rock for geologic repositories of nuclear waste in several nations because it is “dry” and probably “impermeable”. To evaluate the safety of nuclear waste disposal in salt, it is necessary to calculate the rate of release of nuclides from solidified waste form and to predict the transport of released radionuclides. Our objective is to develop analytic methods for such prediction, based on mass transfer theory. First, we present an analysis of pressure‐driven brine migration. After consolidation, brine migration analyzed by these equations and using the particular set of parameter values is of a small magnitude, with Darcy velocities of the order of micrometers per year. Brine migration in consolidated salt is very localized, within a few meters from the waste package, and highly transient. We have analyzed diffusion of radionuclides near waste packages in a salt repository, using analytic equations for low Peclet systems. According to this analysis it is unlikely that any low‐solubility species will have difficulty meeting the U.S. Nuclear Regulatory Commission release rate requirement at the bare waste/salt interface. We have also analyzed the role that an interbed might play in being a preferential pathway for radionuclide migration. We calculate the diffusive mass fluxes from an infinitely long bare waste cylinder in salt, facing an interbed. The fractional release rates of solubility‐limited species into the interbed are low for the parameter values used in the numerical illustrations.

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Mass transfer in a salt repository

Cited by 6 publications

References 8 publications

Brine flow in heated geologic salt.

Brine flow in heated geologic salt.

A review of near-field mass transfer in geologic disposal systems

Analyses of mass transport in a nuclear waste repository in salt

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