Modeling of Thermal-Hydrological-Chemical Laboratory Experiments

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Description

The emplacement of heat-generating nuclear waste in the potential geologic repository at Yucca Mountain, Nevada, will result in enhanced water-rock interaction around the emplacement drifts. Water present in the matrix and fractures of the rock around the drift may vaporize and migrate via fractures to cooler regions where condensation would occur. The condensate would react with the surrounding rock, resulting in mineral dissolution. Mineralized water flowing under gravity back towards the heat zone would boil, depositing the dissolved minerals. Such mineral deposition would reduce porosity and permeability above the repository, thus altering the flow paths of percolating water. The objective ... continued below

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4 pages

Creation Information

Dobson, P. F.; Kneafsey, T. J.; Sonnenthal, E. L. & Spycher, Nicolas May 31, 2001.

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Description

The emplacement of heat-generating nuclear waste in the potential geologic repository at Yucca Mountain, Nevada, will result in enhanced water-rock interaction around the emplacement drifts. Water present in the matrix and fractures of the rock around the drift may vaporize and migrate via fractures to cooler regions where condensation would occur. The condensate would react with the surrounding rock, resulting in mineral dissolution. Mineralized water flowing under gravity back towards the heat zone would boil, depositing the dissolved minerals. Such mineral deposition would reduce porosity and permeability above the repository, thus altering the flow paths of percolating water. The objective of this research is to use coupled thermal-hydrological-chemical (THC) models to simulate previously conducted laboratory experiments involving tuff dissolution and mineral precipitation in a boiling, unsaturated fracture. Numerical simulations of tuff dissolution and fracture plugging were performed using a modified version of the TOUGHREACT code developed at LBNL by T. Xu and K. Pruess. The models consider the transport of heat, water, gas and dissolved constituents, reactions between gas, mineral and aqueous phases, and the coupling of porosity and permeability to mineral dissolution and precipitation. The model dimensions and initial fluid chemistry, rock mineralogy, permeability, and porosity were defined using the experimental conditions. A 1-D plug-flow model was used to simulate dissolution resulting from reaction between deionized water and crushed ash flow tuff. A 2-D model was developed to simulate the flow of mineralized water through a planar fracture within a block of ash flow tuff where boiling conditions led to mineral precipitation. Matrix blocks were assigned zero permeability to confine fluid flow to the fracture, and permeability changes in the fracture were specified using the porosity cubic law relationship.

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4 pages

Notes

INIS; OSTI as DE00786557

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  • Other Information: PBD: 31 May 2001

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  • Report No.: MOL.20010808.0255
  • Grant Number: NONE
  • DOI: 10.2172/786557 | External Link
  • Office of Scientific & Technical Information Report Number: 786557
  • Archival Resource Key: ark:/67531/metadc716823

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  • May 31, 2001

Added to The UNT Digital Library

  • Sept. 29, 2015, 5:31 a.m.

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  • Feb. 10, 2016, 7:43 p.m.

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Dobson, P. F.; Kneafsey, T. J.; Sonnenthal, E. L. & Spycher, Nicolas. Modeling of Thermal-Hydrological-Chemical Laboratory Experiments, report, May 31, 2001; Las Vegas, Nevada. (digital.library.unt.edu/ark:/67531/metadc716823/: accessed August 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.