Nuclide Migration in Fractured or Porous Rock

Rickert, Paul G.; Strickert, Richard G.; Seitz, M.G.

doi:10.1021/bk-1979-0100.ch010

Cited by 5 publications

(4 citation statements)

References 2 publications

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“…Once radionuclides have escaped a repository and reached the country rock, the speed and concentrations with which they reach the biosphere are controlled by the rate of the fluid flow and the physical and chemical environment along its path; in particular the ability of the rock to retard the movement of the radionuclides (Rickert et al, 1979;Chapman and McKinley, 1987). Retardation can be brought about by the process of 'dead-end diffusion'.…”

Section: Nuclear Waste Isolationmentioning

confidence: 99%

Micropores and micropermeable texture in alkali feldspars: geochemical and geophysical implications

1995

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Scanning Electron Microscopy and Transmission Electron Microscopy show that normal, slightly turbid alkali feldspars from many plutonic rocks contain high concentrations of micropores, from ∼1 µm to a few nm in length, typically 0.1 µm. There may be 109 pores mm−3 and porosities as high as 4.75 vol.% have been observed, although ∼1% is typical. Only ‘pristine’ feldspars, which are dark coloured when seen in the massive rock, such as in larvikite and some rapakivi granites, are almost devoid of pores. Weathering enlarges prexisting pores and exploits sub-regularly spaced edge dislocations which occur in semicoherent microperthites, but the underlying textures which lead to skeletal grains in soils are inherited from the high temperature protolith. Most pores are devoid of solid inclusions, but a variety of solid particles has been found. Although the presence of fluid in pores cannot usually be demonstrated directly, crushing experiments have shown that Ar and halogens reside in fluids. Some pores are ‘negative crystals’, often with re-entrants defined by the {110} Adularia habit, while others have curved surfaces often tapering to thin, cusp-shaped apices. The variable shape of pores accounts for the ability of some pores to retain fluid although the texture is elsewhere micropermeable, as shown by 18O exchange experiments.Apart from rare, primary pores in pristine feldspar, pore development is accompanied by profound recrystallization of the surrounding microtexture, with partial loss of coherency in cryptoperthites. This leads to marked ‘deuteric coarsening’ forming patch and vein perthite, and replacement of ‘tweed’ orthoclase by twinned microcline. The Ab- and Or-rich phases in patch perthite are made up of discrete subgrains and the cuspate pores often develop at triple-junctions between them. Coarsened lamellar and vein perthites are composed of microporous subgrain textures. These ‘unzipping’ reactions result from fluid-feldspar interactions, at T <450°C in hypersolvus syenites and T < 350°C in a subsolvus granites, and are driven by elastic strain-energy in coherent cryptoperthites and in tweed textures. Further textural change may continue to surface temperatures. In salic igneous rocks there is a general connection between turbidity and the type of mafic mineral present; pristine alkali feldspars occur in salic igneous rocks with a preponderance of anhydrous mafic phases.Because alkali feldspar is so abundant (and larger, 10 μm pores have previously been described in plagioclase), intracrystal porosity is a non-trivial feature of a large volume of the middle and upper crust. The importance of pores in the following fields is discussed: 39Ar/40Ar dating and ‘thermochronometry’; oxygen exchange; Rb and Sr diffusion; weathering; experimental low-temperature dissolution; development of secondary porosity and diagenetic albitization; leachable sources of metals; nuclear waste isolation; deformation; seismic anisotropy; electrical conductivity. Important questions concern the temperature range of the development of the textures and their stability during burial and transport into the deeper crust.

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Section: Nuclear Waste Isolationmentioning

confidence: 99%

Micropores and micropermeable texture in alkali feldspars: geochemical and geophysical implications

1995

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“…Lap']ace and F_'ourier l_ra}_i_sforms, ''Gauss-Le'geridre integr_t_'on, Radion'u'clide Transport, An_l_tic_l Sol_tion,^ConveGtioo-Disl_ersion_ Diffusion, R_dioa_tiv@ Decaj_, F_ej_a.rd_tioI1,one _umulaz__n_ jwo-u_mAnSve _as_°n@' _i),qcen_ra_on, _nQJe rri}cture, Mult_Dte Fracture, KOCKmazr_x,.Mass Flu> , zso_nE, rma_, vara_lel (Neretnieks, 1980)andadsorptive properties (Rickert et al,, 1979), Analytical solutions for solute transport in planar fractures reported to date are for the most part unidimensional; they neglect in some cases the dispersion phenomena as well as decay reaction at the source, and they are based on the Laplace transformation technique, The first recursive onedimensional solution for dispersion-free transport of a decay chain ofarbitrary length is a single fracture with diffusion into the rock matrix was presented by Kanki et al, (1981) (see also Chambrd et al, 1982. Subsequently a nonrecursive solution for a three-member decay chain neglecting dispersion in the fracture and radioactive decay in the rock matrix was reported by the same authors (see Chambrd et al,, 1982), Neretnieks (1980) reported a solution for the nondispersive transport of a decaying species along a discrete fracture and rock matrix of infinite thickness, and demonstrated the overall impact of the matrix diffusion mechanism on the transport process, Rasmuson and Neretnieks (1980) presented a solution for the radial diffusion problem and longitudinal dispersion in spherical porous particles; their work is an extension of the Rosen (1952) solution, which neglected the dispersion effects, and apparently an improvement of the Babcock et al (1966) solution of the same problem.…”

Section: _mentioning

confidence: 99%

FRACFLO: Analytical solutions for two-dimensional transport of a decaying species in a discrete planar fracture and equidistant multiple parallel fractures with rock matrix diffusion

Gureghian¹

1990

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“…This sttuation has partly resulted because finite rates of mass transfer between phases must be considered. In this regard, recent works of interest include those of Rickert, Strickert and Seitz [1]; Friedman and Fried [2]; Hinkebein [3]; Nerentnieks [4,5]; and Rasmuson and Nerentnieks [6). An earlier, paper [7] briefly summarized initial work conducted to develop theoretical and experimental approaches which will provide a basis for analyzing radionuclide transport in jointed geologic media.…”

Section: Introductionmentioning

confidence: 99%

“…These expressions must then be incorporated into the appropriate terms in Eqs. [1][2][3][4], and the resulting models simplified such that subsequent analyses will be sufficiently accurate and computationally feasible. In the following section, an experimental approach which is being developed to identify and study such phenomena is discussed, and some initial results are given.…”

Section: Introductionmentioning

confidence: 99%

Fundamental approach to the analysis of radionuclide transport resulting from fluid flow through jointed media

Erickson¹

1981

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Nuclide Migration in Fractured or Porous Rock

Cited by 5 publications

References 2 publications

Micropores and micropermeable texture in alkali feldspars: geochemical and geophysical implications

Micropores and micropermeable texture in alkali feldspars: geochemical and geophysical implications

FRACFLO: Analytical solutions for two-dimensional transport of a decaying species in a discrete planar fracture and equidistant multiple parallel fractures with rock matrix diffusion

Fundamental approach to the analysis of radionuclide transport resulting from fluid flow through jointed media

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