Near-field/altered-zone models report

Hardin, Ernest

doi:10.2172/16725

Cited by 17 publications

(34 citation statements)

References 267 publications

(398 reference statements)

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“…Matyskiela (1997) estimates enhanced fracture flow to be as much as five times ambient conditions. This behavior is opposite to formation of a silica cap that has been predicted by recent simulations, in which fractures would become filled with quartz (or chalcedony) and further flow would be inhibited (Hardin, 1998). Thus a direct contradiction would appear to exist between modeling results and field observations purporting to represent an analogue of the repository environment.…”

Section: 21mentioning

confidence: 56%

“…It is not clear, however, what effec~if any, these fluid fluxes will have on mineral alteration. This thermal period is expected to last for, at most, several thousand years with relatively low liquid fluxes (Lichtner and Seth, 1996;Hardin, 1998 heat released from the decay of radioactive waste-range from little or no alteration at all, to extensive alteration with the formation of a silica cap above the repository and alteration of feldspars, silica polymorphs, and glass to zeolites and clay minerals (Hardin, 1998;Whitbeck and Glassley, 1998;Nitao, 1998). The latter strong alteration scenario could result in significant changes in porosity and permeability of the repository host rock that could affect its performance, both favorably and unfavorably.…”

Section: Thc Coupled Processes Associated With the Proposed Yucca Moumentioning

confidence: 99%

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A Natural Analogue for Thermal-Hydrological-Chemical Coupled Processes at the Proposed Nuclear Waste Repository at Yucca Mountain, Nevada

Carey¹,

Keating²,

Lichtner³

1999

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Section: 21mentioning

confidence: 56%

Section: Thc Coupled Processes Associated With the Proposed Yucca Moumentioning

confidence: 99%

A Natural Analogue for Thermal-Hydrological-Chemical Coupled Processes at the Proposed Nuclear Waste Repository at Yucca Mountain, Nevada

Carey¹,

Keating²,

Lichtner³

1999

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“…Water undergoing boiling or evaporation or reacting with precipitated salts is predicted to become concentrated in a number of dissolved constituents either in close proximity to, or within, potential emplacement drifts (Hardin 1998 Because mineral precipitation occurs throughout these calculations (calcite, silica polymorphs, etc. ), these compositions do not represent simply concentrated ambient values, but are selectively concentrated.…”

Section: Potential Brines and Salt Precipitates At Yucca Mountainmentioning

confidence: 99%

In-Drift Precipitates/Salts Model

Mariner¹

2003

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Revision to qualify and document major improvements to the In-Drift Precipitates/Salts model. These improvements include the use of a new software version of EQ3/6 (version 8.0) and a new Pitzer database, which together are designed to predict aqueous chemical reactions in highly concentrated brines. Additional model validation simulations are included for deliquescence points and the evaporation of seawater. Overall model uncertainties are estimated for output parameters used in TSPA-LA. These changes were extensive and required a full revision of the document. OFFICE OF CIVILIAN RADIOACTIVE WASTE MANAGEMENT MODEL REVISION RECORD ACKNOWLEDGMENTSTwo key contributions to this document must be acknowledged. One is the Pitzer thermodynamic database developed and documented in Attachment I. Carlos Jove-Colon with the assistance of Tom Wolery, Joseph Rard, Ananda Wijesinghe, and Russell Jarek developed the Pitzer database and provided the documentation included in Table 3, Table 4, and Attachment I. The other key contribution is the mineral suppression methodology presented in Section 6.6.2.6. This methodology was developed by Darren Jolley with the assistance of Richard Metcalf.The work presented in this document was supported by the Office of Repository Design as part of the Civilian Radioactive Waste Management Program, managed by the U.S. Department of Energy.In-Drift Precipitates/Salts Model Example The scope of this document is to develop, describe, and validate the IDPS model. This model is a quasi-equilibrium model. All reactions proceed to equilibrium except for several suppressed minerals in the thermodynamic database not expected to form under the proposed repository conditions within the modeling timeframe. In this revision, upgrades to the EQ3/6 code (Version 8.0) and Pitzer thermodynamic database improve the applicable range of the model. These new additions allow equilibrium and reaction-path modeling of evaporation to highly concentrated brines for potential water compositions of the system Na-K-H-Mg-Ca-Al-Cl-F-NO 3 -SO 4 -Br-CO 3 -SiO 2 -CO 2 -O 2 -H 2 O at temperatures in the range of 0ºC to 125ºC, pressures in the atmospheric range, and relative humidity in the range of 0 to100 percent. This system applies to oxidizing conditions only, and therefore limits the model to applications involving oxidizing conditions.A number of thermodynamic parameters in the Pitzer database have values that have not been determined or verified for the entire temperature range. In these cases, the known values are used to approximate the values for the rest of the temperature range. Although such treatment contributes to uncertainty in model outputs, the model validation test cases indicate that the model, with its associated uncertainty, is valid for its intended use.The intended use of this model is to estimate and tabulate, within an appropriate level of confidence, the effects of evaporation, deliquescence, and potential environmental conditions on the pH, ionic strength, and chemical compositions of water an...

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“…As the repository heating rate further decreases, the rewetting period begins as temperature, liquid-phase saturation and relative humidity begin to slowly return to ambient values. A more detailed description and discussion of the near-field thermal hydrology can be found in Buscheck et al (1997) and Hardin, et al (1998).…”

Section: Thermal Hydrologymentioning

confidence: 99%

“…Values used for rate constant, activation energy and surface area are given in Table 3. Temperature and flow fields for the 2D study were taken directly from drift-scale thermohydrologic simulations for a reference case repository design using a coupled thermal hydrological computer code (NUFT) (Nitao, 1995;Hardin et al, 1998). The NUFT simulations were run using a dual permeability formulation to describe the fracture-matrix system.…”

Section: Model Setupmentioning

confidence: 99%

Predicting mineral alteration at the potential nuclear waste repository at Yucca Mountain, NV with reactive transport modeling

Glassley¹

1998

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April 1998This is an informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-ENG-48. DISCLAIMERThis document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.This report has been reproduced directly from the best available copy. ABSTRACTWe present the results of a reactive transport modeling study that examines the sensitivity of mineral evolution to temperature, condensate properties and water flow conditions anticipated to occur in the potential Yucca Mountain nuclear waste repository site. We have investigated a key aspect of the thermal-hydrological repository system, the interaction of condensate water flowing through fractures at the site. Future simulations will include mineral changes at the boiling front, a process not considered in this study.Our simulations show that the principal mineral changes that occur are dissolution of the initial phases (mainly calcite, but also feldspars and clay) and formation of zeolites and hydrated aluminous phases. Major differences in mineral alteration occur over very short distances. Fracture mineral alteration is clearly coupled with the thermal hydrological environment. Fracture porosity is enhanced in those areas where condensate forms, an upper, lower temperature condensate zone and a lower, high temperature condensate zone. The locations where mineral precipitation occur and porosity decreases depend on the integrated residence time of the solution on the fracture surface. In general, mineral precipitation is expected to occur in the region ~150 m above the water table. Whether the changes in porosity are significant enough to modify thermohydrological behavior remains to be evaluated.

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Near-field/altered-zone models report

Cited by 17 publications

References 267 publications

A Natural Analogue for Thermal-Hydrological-Chemical Coupled Processes at the Proposed Nuclear Waste Repository at Yucca Mountain, Nevada

A Natural Analogue for Thermal-Hydrological-Chemical Coupled Processes at the Proposed Nuclear Waste Repository at Yucca Mountain, Nevada

In-Drift Precipitates/Salts Model

Predicting mineral alteration at the potential nuclear waste repository at Yucca Mountain, NV with reactive transport modeling

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