Analytical Performance Models for Geologic Repositories

Pigford, T.H.; Fujita, A.; Kanki, Tatsuo; Kobayashi, Akira; Lung, H.; Ting, Du; Sato, Yukihiko; Savoshy, S.J.

doi:10.2172/876188

Cited by 29 publications

(23 citation statements)

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“…To evaluate the role ~f packing, it proves convenient to report the reduced fractional release rate, f /f • or the ratio of the fractional rele~seOrates with and without packing: transpgrt is by diffusion in the packing and convection 1n the medium. In this large Pe regime, f approaches a constant asymptote character~stic of diffusion in the packing while f increases as fie (2). Accordingly, in Figure I~ f If decreases as lIne in the high Pe rangi.…”

Section: Theorymentioning

confidence: 85%

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Steady Radionuclide Release Rates from a Bentonite-Protected Waste Canister

Jensen¹,

Radke²

1987

Coupled Processes Associated With Nuclear Waste Repositories

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A bentonite-based packing or engineered barrier is one ingredient of the multibarrier concept for underground storage of high-level nuclear waste. This paper investigates the possible effectiveness that such a smectiteladen barrier might have in controlling steady, solubility-limited release rates from a cylindrical waste canister.Darcy's law and the convective-diffusion equation in two dimensions are solved numerically with and without an annulus of packing material. Reduced fractional release rates quantifying the role of the packing are studied over wide ranges of ground water velocities, packing amounts, and packing permeability and effective diffusivity. Release rates are shown to be strongly dependent on the physical properties of the packing, particularly the effective diffusivity.Although the low permeability of a bentonite-rich packing negates convection next to the canister, calculated release rates of the packing-protected waste canister do not differ dramatically from the those for the unprotected canister, except at high ground water velocities. To afford more protection, consideration must be given to reducing the porosity of the packing material.

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Section: Theorymentioning

confidence: 85%

“…In a mature repository approaching steady conditions, the low hydraulic permeability of 1 [2). Since repository life times must be orders of magnitude longer, a steady analysis of radionuclide release is useful [3,12).…”

Section: Introductionmentioning

confidence: 99%

Steady Radionuclide Release Rates from a Bentonite-Protected Waste Canister

Jensen¹,

Radke²

1987

Coupled Processes Associated With Nuclear Waste Repositories

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“…The transport of radionuclides in discrete fractures with matrix diffusion has been investigated since the 1980s, and mathematical solutions were obtained by various researchers (Neretnieks, 1980;Tang et al, 1981;Chambre et al, 1982;Sudicky and Frind, 1984). Hodgkinson and Maul (1988) developed a 1-D model for the transport of radionuclides through a single type of permeable or fractured rock using the numerical inversion of Laplace transforms.…”

Section: Previous Studiesmentioning

confidence: 99%

Effects of depth on transport of 129I in crystalline rock

Oruçoğlu

Akker

Ahn

2014

Annals of Nuclear Energy

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a b s t r a c tIn the present paper, a model for the transport of iodine through fractures in granitic rock has been developed by taking into account the variation of parameters with depth in order to investigate the effects of depth on repository performance. First, the evolution of groundwater chemistry with depth has been modeled by considering the physical and chemical conditions that vary with depth. Second, iodine-water interactions and iodine-rock interactions under groundwater-chemistry evolution with depth in crystalline rocks have been modeled using PHREEQC, with which the distribution coefficients of iodine have been numerically evaluated as a function of depth. These values and other depth-dependent parameters such as fracture aperture, groundwater velocity, and diffusion coefficients have been used in the iodine transport simulation to observe differences in the iodine concentration in the water from repositories located at 500 and 1000 m depths. The results show that iodine stays within the vicinity of the repository if it is disposed of at a greater depth. The main reason is that the retention effect of matrix diffusion increases and relative contribution of advection along fractures decreases at depth due to the cubic law for the water flow velocity in fractures.

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“…Later, assuming that the container is not present, there is mass transfer of dissolved radionuclides from the cored edge of the interbed into the interbed flow stream. This problem of diffusive-convective mass transfer for flow in a porous medium surrounding a cylinder, conservatively assuming saturation concentration in the liquid at the cylinder surface, has already been analyzed by Chambre' [18][19][20].…”

Section: Effect Of Flow In Interbeds Intersecting Bore Holesmentioning

confidence: 99%