Total-system performance assessment for Yucca Mountain - SNL second iteration (TSPA-1993); Volume 2

Wilson, Michael L.; Barnard, R.W.; Barr, G.E.; Dockery, Holly A.; Dunn, E.; Eaton, R. Philip; Martinez, Mario J.; Gauthier, John H.; Guerin, D.C.; Lu, Norman

doi:10.2172/145216

Cited by 18 publications

(8 citation statements)

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“…Thus uncertainty in the fracture aperture distribution was constrained by adjusting the limits of fracture aperture distribution to minimum and maximum values of 1 Â 10 À6 and 1.5 mm, respectively, while matching measured fracture domain permeability given in Table 1. The mean value of the fracture aperture distribution shown in Table 1 is 0.031 mm, which is slightly smaller than the hydraulic aperture estimated by Wilson et al [1993] and CRWMS M&O [2000]. Model calculations reveal that under unsaturated conditions the results were not sensitive to upper and lower bounds of aperture size distribution (other than the expected impact on permeability at saturation of larger apertures).…”

Section: Comparisons With Previous Models and Sensitivity Analysesmentioning

confidence: 63%

“…For the first type, Barton et al [1993] measured representative mechanical apertures for many fractures on cleared pavements; however, these fractures likely include the effects of surficial processes. For the second type of aperture data, Wilson et al [1993] used borehole fracture spacing and air permeability data combined with the cubic law for flow in a fracture plane to generate Monte Carlo realizations of hydraulic aperture distributions following the beta function. They used minimum and maximum hydraulic apertures of 0.064 and 1.14 mm, and estimated a mean hydraulic aperture of 0.18 mm.…”

Section: Comparisons With Previous Models and Sensitivity Analysesmentioning

confidence: 99%

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Seepage into drifts and tunnels in unsaturated fractured rock

Tuller

Fedors

2005

Water Resources Research

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[1] Methods for obtaining estimates of seepage into drifts and tunnels excavated in unsaturated fractured rocks are of interest for engineering and environmental applications. For uniform porous media a tunnel surface may present a capillary barrier promoting water diversion around the opening through the porous matrix, hence reducing seepage into the opening. The presence of fractures intersecting the opening complicates flow behavior and presents a challenge to seepage prediction. We present a simple and physically based model for seepage estimation that preserves key physical processes associated with fracture flow, while avoiding complexity of detailed fracture network characterization. The processes of film and capillary-driven flows are combined with a geometrically tractable representation of the dual-continuum fractured rock with two disparate populations of matrix pores and fracture apertures. The large disparity in capillary forces between matrix and fractures rules out matrix seepage based on Philip's theory. We obtain estimates of seepage fraction for a given percolation flux from consideration of the hydraulic conductivity of the fracture domain only. Similar to previous studies, the new model shows existence of a percolation threshold for onset of seepage. The new model also exhibits a steep increase in seepage with increase in percolation flux that reflects the role of fracture film flow. In addition to consideration of physically based flow processes, computations for the proposed analytical model can be performed with common spreadsheet software, which is a distinct advantage over numerical equivalent porous media approaches that require a powerful computational environment, excessive computation time, and thorough characterization of the fracture domain.Citation: Or, D., M. Tuller, and R. Fedors (2005), Seepage into drifts and tunnels in unsaturated fractured rock, Water Resour. Res., 41, W05022,

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Section: Comparisons With Previous Models and Sensitivity Analysesmentioning

confidence: 63%

Section: Comparisons With Previous Models and Sensitivity Analysesmentioning

confidence: 99%

Seepage into drifts and tunnels in unsaturated fractured rock

Tuller

Fedors

2005

Water Resources Research

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“…flux[Wilson et al, 1994;Pruess et al, 1997]. The water flux in fractures is considered to be mainly dependent on fracture saturation because fracture water flow is gravitydominated.…”

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confidence: 99%

An active fracture model for unsaturated flow and transport in fractured rocks

Liu¹,

Doughty²,

Bodvarsson³

1998

Water Resources Research

188

201

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Abstract. The unsaturated zone at Yucca Mountain, a potential repository site of highlevel nuclear waste, is a complex hydrologic system in which a variety of important flow and transport processes is involved. To quantify these processes as accurately as possible is a theoretically challenging and practically important issue. In this study, we propose a new formulation for modeling flow and transport in unsaturated fractured rocks. The formulation is mainly based on a hypothesis that only a portion of connected fractures are active in conducting water. Analysis of the relevant data with the new formulation suggests that about 18-27% of the connected fractures in the Topopah Spring welded (TSw) unit (the potential repository unit) of Yucca Mountain are active under ambient conditions. The relatively high percentage of active fractures is consistent with field observations from a variety of sources. Sensitivity analyses are performed to investigate effects of the "activity" of connected fractures on flow and transport behavior in unsaturated rocks.

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“…As mentioned above, the total area of the repository is currently estimated to be about 6 km 2. The area radioactive waste occupies within repository depends on design but varies from about 2.3 km 2 for a high thermal load repository to 4.6 km 2 for a lower thermal load repository [Wilson et al, 1994]. Our calculations have been for 8 km2, which includes the total area of the repository and a buffer zone extending 500 m out from the repository perimeter.…”

Section: Probability Of Volcanic Disruption Of the Proposed Yucca Moumentioning

confidence: 99%

Three nonhomogeneous Poisson models for the probability of basaltic volcanism: Application to the Yucca Mountain region, Nevada

Connor¹,

Hill²

1995

J. Geophys. Res.

163

153

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The distribution and timing of areal basaltic volcanism are modeled using three nonhomogeneous methods: spatio‐temporal nearest neighbor, kernel, and nearest‐neighbor kernel. These models give nonparametric estimates of spatial or spatio‐temporal recurrence rate based on the positions and ages of cinder cones and related vent structures and can account for migration and shifts in locus, volcano clustering, and development of regional vent alignments. The three methods are advantageous because (1) recurrence rate and probability maps can be made, facilitating comparison with other geological information; (2) the need to define areas or zones of volcanic activity, required in homogeneous approaches, is eliminated; and (3) the impact of uncertainty in the timing and distribution of individual events is particularly easy to assess. The models are applied to the Yucca Mountain region (YMR), Nevada, the site of a proposed high‐level radioactive waste repository. Application of the Hopkins F test, Clark‐Evans test, and K function indicates volcanoes cluster in the YMR at the >95% confidence level. Weighted‐centroid cluster analysis indicates that Plio‐Quaternary volcanoes are distributed in four clusters: three of these clusters include cinder cones formed <1 Ma. Probability of disruption within the 8 km2 area of the proposed repository by formation of a new basaltic vent is calculated to be between 1 × 10−4 and 5 × 10−4 in 104 years (the kernel and nearest‐neighbor kernel methods give a maximum probability of 5 × 10−4 in 104 years), assuming regional recurrence rates of 5–10 volcanoes/m.y. An additional finding, illustrating the strength of nonhomogeneous methods, is that maps of the probability of volcanic eruption for the YMR indicate the proposed repository lies on a steep probability gradient: volcanism recurrence rate varies by more than 2 orders of magnitude within 20 km. Insight into this spatial scale of probability variation is a distinct benefit of application of these methods to hazard analysis in areal volcanic fields.

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Total-system performance assessment for Yucca Mountain - SNL second iteration (TSPA-1993); Volume 2

Cited by 18 publications

References 0 publications

Seepage into drifts and tunnels in unsaturated fractured rock

Seepage into drifts and tunnels in unsaturated fractured rock

An active fracture model for unsaturated flow and transport in fractured rocks

Three nonhomogeneous Poisson models for the probability of basaltic volcanism: Application to the Yucca Mountain region, Nevada

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