Analysis of thermohydrologic behavior for above-boiling and below-boiling thermal-operating modes for a repository at Yucca Mountain

Buscheck, Thomas A.; Rosenberg, N.D.; Blink, J.A.; Sun, Yunwei; Gansemer, J.

doi:10.1016/s0169-7722(02)00156-0

Cited by 13 publications

(8 citation statements)

References 10 publications

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“… Buscheck et al [2002, 2003] also employed a multiscale TH model to evaluate repository performance for different designs with respect to thermal design goals (e.g., keeping waste containers dry). In the locally boiling or globally boiling thermal design under consideration, a considerable volume of rock mass around the emplacement drifts would be above the boiling point of water for hundreds to thousands of years.…”

Section: Impact Of Th Processes On Key Repository Performance Issuesmentioning

confidence: 99%

“…In the subboiling thermal design, the host rock temperature would be below the boiling point everywhere and at all times. This multiscale modeling approach [ Buscheck et al , 2002, 2003] meets the objective of simultaneously accounting for processes occurring at the scale of a few tens of centimeters around individual waste containers within emplacement drifts and at the multikilometer scale of the mountain. A number of simplifying assumptions were made to employ this model as a cost‐effective numerical tool for conducting a large number of realizations.…”

Section: Impact Of Th Processes On Key Repository Performance Issuesmentioning

confidence: 99%

“…This multiscale model was used to evaluate repository performance with respect to a number of design options, with a range of values for the associated thermal design parameters. Buscheck et al [2002, 2003] simulate the in‐drift TH conditions (specifically, temperature and relative humidity) in representative host rock repository units, with selected locations accounting for the effect of repository edge cooling for different waste container types and emplacement options. Temperature and humidity parameters within the waste emplacement drifts are controlling factors on the potential for waste container corrosion and, in turn, repository performance.…”

Section: Impact Of Th Processes On Key Repository Performance Issuesmentioning

confidence: 99%

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Modeling of thermally driven hydrological processes in partially saturated fractured rock

Tsang¹,

Birkhölzer²,

Mukhopadhyay³

2009

Reviews of Geophysics

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[1] This paper is a review of the research that led to an indepth understanding of flow and transport processes under strong heat stimulation in fractured, porous rock. It first describes the anticipated multiple processes that come into play in a partially saturated, fractured porous volcanic tuff geological formation when it is subject to a heat source such as that originating from the decay of radionuclides. The rationale is then given for numerical modeling being a key element in the study of multiple processes that are coupled. The paper outlines how the conceptualization and the numerical modeling of the problem evolved, progressing from the simplified to the more realistic. Examples of numerical models are presented so as to illustrate the advancement and maturation of the research over the last 2 decades. The most recent model applied to in situ field thermal tests is characterized by (1) incorporation of a full set of thermal-hydrological processes into a numerical simulator, (2) realistic representation of the field test geometry in three dimensions, and (3) use of site-specific characterization data for model inputs. Model predictions were carried out prior to initiation of data collection, and the model results were compared to diverse sets of measurements. The approach of close integration between modeling and field measurements has yielded a better understanding of how coupled thermal hydrological processes produce redistribution of moisture within the rock, which affects local permeability values and subsequently the flow of liquid and gases. The fluid flow, in turn, will change the temperature field. We end with a note on future research opportunities, specifically those incorporating chemical, mechanical, and microbiological factors into the study of thermal and hydrological processes.

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Section: Impact Of Th Processes On Key Repository Performance Issuesmentioning

confidence: 99%

Section: Impact Of Th Processes On Key Repository Performance Issuesmentioning

confidence: 99%

Section: Impact Of Th Processes On Key Repository Performance Issuesmentioning

confidence: 99%

See 1 more Smart Citation

Modeling of thermally driven hydrological processes in partially saturated fractured rock

Tsang¹,

Birkhölzer²,

Mukhopadhyay³

2009

Reviews of Geophysics

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“…The code would later be developed into the TOUGH2 code [ Pruess et al , 1999] and extended with other TOUGH family codes that would be extensively applied throughout the Yucca Mountain Project. An alternative code called NUFT, developed at the Lawrence Livermore National Laboratory, was also extensively applied to model thermal‐hydrological (TH) processes at Yucca Mountain from the early 1990s [ Buscheck et al , 1996, 2003; Nitao , 1998]. The TOUGH2 and NUFT codes were applied to develop models of the partially saturated fractured rock at Yucca Mountain based on the concept of multiple overlapping continua or dual permeability, including flow properties for both fracture and matrix continua.…”

Section: Introductionmentioning

confidence: 99%

Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain

Rutqvist

Tsang

2012

Reviews of Geophysics

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The site investigations at Yucca Mountain, Nevada, have provided us with an outstanding data set, one that has significantly advanced our knowledge of multiphysics processes in partially saturated fractured geological media. Such advancement was made possible, foremost, by substantial investments in multiyear field experiments that enabled the study of thermally driven multiphysics and testing of numerical models at a large spatial scale. The development of coupled‐process models within the project have resulted in a number of new, advanced multiphysics numerical models that are today applied over a wide range of geoscientific research and geoengineering applications. Using such models, the potential impact of thermal‐hydrological‐mechanical (THM) multiphysics processes over the long‐term (e.g., 10,000 years) could be predicted and bounded with some degree of confidence. The fact that the rock mass at Yucca Mountain is intensively fractured enabled continuum models to be used, although discontinuum models were also applied and are better suited for analyzing some issues, especially those related to predictions of rockfall within open excavations. The work showed that in situ tests (rather than small‐scale laboratory experiments alone) are essential for determining appropriate input parameters for multiphysics models of fractured rocks, especially related to parameters defining how permeability might evolve under changing stress and temperature. A significant laboratory test program at Yucca Mountain also made important contributions to the field of rock mechanics, showing a unique relation between porosity and mechanical properties, a time dependency of strength that is significant for long‐term excavation stability, a decreasing rock strength with sample size using very large core experiments, and a strong temperature dependency of the thermal expansion coefficient for temperatures up to 200°C. The analysis of in situ heater experiments showed that fracture closure/opening caused by changes in normal stress across fractures was the dominant mechanism for thermally induced changes in intrinsic fracture permeability during rock mass heating/cooling and that fracture shear dilation appears to be less significant. Significant effort was devoted to predicting the long‐term stability of underground excavations under (mechanical) strength degradation and seismic loading, perhaps one of the most challenging tasks within the project. We note that such long‐term strength degradation is actually an example of a chemically mediated process governed by underlying (microscopic) stress corrosion and chemical diffusion processes. In the Yucca Mountain Project, such chemically mediated mechanical changes were considered implicitly through model calibrations against laboratory and in situ heater experiments at temperatures anticipated to be experienced by the rock. A possible future research direction would be to simulate such processes mechanistically in a complete coupled THMC framework where C denotes chemical processes.

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“…Accompanying these investigations was the development of numerical models of the various components of the natural system, including the vadose zone and the saturated zone. A host of models were developed investigating various aspects of the unsaturated zone (UZ) behavior, with modeling approaches selected to optimize the effectiveness of the modeling tool for specific purposes, including unsaturated flow (Pruess, 1991; Nitao, 1996; Zyvoloski et al, 1997), coupled processes (Bower and Zyvoloski, 1997; Valentine et al, 2002, Rutqvist et al, 2002; Buscheck et al, 2003), reactive transport (Viswanathan et al, 1998; Robinson et al, 2000; Xu et al, 2008), and radionuclide transport for Performance Assessment analyses (Robinson et al, 2003). For the representation of UZ radionuclide transport in Total System Performance Assessment (TSPA) models, an approach was required that enabled the complex, three‐dimensional behavior of the system to be captured in a probabilistic setting in which multiple realizations of system behavior, of which UZ transport was only one part, were performed.…”

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confidence: 99%

Simulation of Radionuclide Transport through Unsaturated, Fractured Rock: Application to Yucca Mountain, Nevada

Robinson

Chu

Lü

2012

Vadose Zone Journal

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This paper describes the numerical methods developed to simulate the transport of radionuclides through the unsaturated, fractured rock below the proposed repository at the Yucca Mountain. Regardless of the disposition of the Yucca Mountain License Application, this method has general applicability for modeling contaminant transport through deep vadose zones. Using a dual‐permeability solution for fluid flow as a basis, the transport model represents contaminant transport with a cell‐based particle‐tracking technique in which particles move from cell to cell in the three‐dimensional large‐scale grid of two overlapping continua. Particle movement between cells, and the residence time within a cell, is computed probabilistically based on transfer functions using numerical solutions of the transport equations for an idealized fracture‐matrix system. Using this approach, the following transport phenomena are simulated: advection through fracture and matrix continua, including between these continua, dispersion, sorption of dissolved radionuclides to the matrix continuum, and within the fault zones, and molecular diffusion between the fractures and matrix. In addition to providing a realistic representation of the relevant processes, this method has the virtue of computational efficiency. After describing the numerical method, this paper presents sensitivity analyses for radionuclide transport travel time distributions from the proposed repository to the water table through the unsaturated zone for the Yucca Mountain system.

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Analysis of thermohydrologic behavior for above-boiling and below-boiling thermal-operating modes for a repository at Yucca Mountain

Cited by 13 publications

References 10 publications

Modeling of thermally driven hydrological processes in partially saturated fractured rock

Modeling of thermally driven hydrological processes in partially saturated fractured rock

Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain

Simulation of Radionuclide Transport through Unsaturated, Fractured Rock: Application to Yucca Mountain, Nevada

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