Assessment of radionuclide vapor-phase transport in unsaturated tuff

doi:10.2172/60027

Title: Assessment of radionuclide vapor-phase transport in unsaturated tuff

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Abstract

This report describes bounding calculations performed to investigate the possibility of radionuclide migration in a vapor phase associated with the emplacement of high-level waste canister in unsaturated tuff formations. Two potential radionuclide transport mechanisms in the vapor phase were examined: aerosol migration and convection/diffusion of volatile species. The former may have significant impact on the release of radionuclides to the accessible environment as the concentration in the aerosols will be equal to that in the ground water. A conservative analysis of air diffusion in a stagnant liquid film indicated that for all expected repository conditions, aerosol formation is not possible. The migration of volatile species was examined both in the vicinity of a waste canister and outside the thermally disturbed zone. Two-dimensional (radial) and three-dimensional (radial-vertical) coupled heat transfer-gas flow-liquid flow simulations were performed using the TOUGH computer code. The gas flow rate relative to the liquid flow rate predicted from the simulations allowed calculations of mobility ratios due to convection which led to the conclusion that, except for the immediate region near the canister, transport in the liquid phase will be dominant for radionuclides heavier than radon. Near the waste canister, iodine transport may also be important in themore »« less

Authors:: Smith, D.M.; Updegraff, C.D.; Bonano, E.J.; Randall, J.D.

Publication Date:: Sat Nov 01 00:00:00 EST 1986

Research Org.:: Sandia National Labs., Albuquerque, NM (United States)

OSTI Identifier:: 60027

Report Number(s):: NUREG/CR-4693; SAND-86-1598
ON: TI87003446

DOE Contract Number:: AC04-76DP00789

Resource Type:: Technical Report

Resource Relation:: Other Information: PBD: Nov 1986

Country of Publication:: United States

Language:: English

Subject:: 05 NUCLEAR FUELS; TUFF; RADIONUCLIDE MIGRATION; VAPORS; AEROSOLS; CONVECTION; DIFFUSION; HEAT TRANSFER; LIQUID FLOW; GAS FLOW; IODINE; GROUND WATER; VOLATILITY; HIGH-LEVEL RADIOACTIVE WASTES; Yucca Mountain Project

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                    Smith, D.M., Updegraff, C.D., Bonano, E.J., and Randall, J.D. Assessment of radionuclide vapor-phase transport in unsaturated tuff.  United States: N. p., 1986. 
        Web.  doi:10.2172/60027.

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                    Smith, D.M., Updegraff, C.D., Bonano, E.J., & Randall, J.D. Assessment of radionuclide vapor-phase transport in unsaturated tuff.  United States.  doi:10.2172/60027.

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                    Smith, D.M., Updegraff, C.D., Bonano, E.J., and Randall, J.D. Sat .  
        "Assessment of radionuclide vapor-phase transport in unsaturated tuff".  United States.  
        doi:10.2172/60027.  https://www.osti.gov/servlets/purl/60027.

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@article{osti_60027,

  title        = {Assessment of radionuclide vapor-phase transport in unsaturated tuff},

  author       = {Smith, D.M. and Updegraff, C.D. and Bonano, E.J. and Randall, J.D.},

  abstractNote = {This report describes bounding calculations performed to investigate the possibility of radionuclide migration in a vapor phase associated with the emplacement of high-level waste canister in unsaturated tuff formations. Two potential radionuclide transport mechanisms in the vapor phase were examined: aerosol migration and convection/diffusion of volatile species. The former may have significant impact on the release of radionuclides to the accessible environment as the concentration in the aerosols will be equal to that in the ground water. A conservative analysis of air diffusion in a stagnant liquid film indicated that for all expected repository conditions, aerosol formation is not possible. The migration of volatile species was examined both in the vicinity of a waste canister and outside the thermally disturbed zone. Two-dimensional (radial) and three-dimensional (radial-vertical) coupled heat transfer-gas flow-liquid flow simulations were performed using the TOUGH computer code. The gas flow rate relative to the liquid flow rate predicted from the simulations allowed calculations of mobility ratios due to convection which led to the conclusion that, except for the immediate region near the canister, transport in the liquid phase will be dominant for radionuclides heavier than radon. Near the waste canister, iodine transport may also be important in the vapor phase. Bounding calculations for vertical mobility ratios were carried out as a function of saturation. These calculations are conservative and agree well with the two-dimensional simulations. Based on this analysis, it is clear that vapor-phase transport will not be important for radionuclides such as cesium and heavier species. Vapor transport for iodine may play a role in the overall release scenario depending on the particular repository conditions.},

  doi          = {10.2172/60027},

  journal      = {},

  number       = ,

  volume       = ,

  place        = {United States},

  year         = {Sat Nov 01 00:00:00 EST 1986},

  month        = {Sat Nov 01 00:00:00 EST 1986}

}

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DOI: 10.2172/60027

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Preliminary assessment of radionuclide vapor phase transport in unsaturated tuff

Smith, D.M. ; Updegraff, C.D. ; Bonano, E.J.

The possibility of radionuclide migration in the vapor phase for unsaturated tuff has been investigated. Radionuclide movement could be the result of either aerosol migration or convection/diffusion of volatile species. A diffusion model for supersaturation of air in tuff groundwater indicates that there is no possibility of aerosol formation under expected repository conditions. An assessment of migration due to convection/diffusion requires solution of the coupled heat transfer-vapor flow-liquid flow problem around a waste canister. The TOUGH code has been used to calculate spatial and temporal distributions of liquid and vapor velocity, saturation and temperature for typical tuff formation properties. Thesemore »« less
Preliminary assessment of radionuclide vapor phase transport in unsaturated tuff

Smith, D.M. ; Updegraff, C.D. ; Bonano, E.J.

The possibility of radionuclide migration in the vapor phase for unsaturated tuff has been investigated. Radionuclide movement could be the result of either aerosol migration or convection/diffusion of volatile species. A diffusion model for supersaturation of air in tuff groundwater indicates that there is no possibility of aerosol formation under expected repository conditions. An assessment of migration due to convection/diffusion requires solution of the coupled heat transfer-vapor flow-liquid flow problem around a waste canister. The TOUGH code has been used to calculate spatial and temporal distributions of liquid and vapor velocity, saturation and temperature for typical tuff formation properties. Thesemore »« less
Radionuclide transport as vapor through unsaturated fractured rock. [Contains glossary]

Green, R.T. ; Evans, D.D.

Transport mechanisms potentially important at larger distances include ordinary diffusion, viscous flow, and free convection. Ordinary diffusion includes self and binary diffusion, Knudsen flow, and surface diffusion. Pressure flow and slip flow comprise viscous flow. Free convective flow results from a gas density contrast. Transport mechanisms or processes dominant near the repository include ordinary diffusion, viscous flow plus several mechanisms whose driving forces arise from the non-isothermal, radioactive nature of high-level waste. The additional mechanisms include forced diffusion, aerosol transport, thermal diffusion and thermophoresis. Near a repository, vapor transport mechanisms and processes can provide a significant means of transport frommore »« less
RADIONUCLIDE MIGRATION IN TUFF UNDER UNSATURATED CONDITIONS

T.T. Vandergraaf

An understanding of the transport of radionuclides through unsaturated and saturated tuffaceous material is essential in assessing the safety of the proposed high-level waste repository at Yucca Mountain. Migration experiments with conservative and chemically reactive non-radioactive tracers have been performed at the Busted Butte Unsaturated Zone underground facility, SE of Yucca Mountain, and with radionuclides in columns of crushed tuff at the Los Alamos National Laboratory. In this paper, complementary radionuclide migration experiments, performed under unsaturated conditions in a small block of tuff excavated from Busted Butte, are described.
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Auxiliary analyses in support of performance assessment of a hypothetical low-level waste facility: Two-phase flow and contaminant transport in unsaturated soils with application to low-level radioactive waste disposal. Volume 2

Binning, P. ; Celia, M.A. ; Johnson, J.C.

A numerical model of multiphase air-water flow and contaminant transport in the unsaturated zone is presented. The multiphase flow equations are solved using the two-pressure, mixed form of the equations with a modified Picard linearization of the equations and a finite element spatial approximation. A volatile contaminant is assumed to be transported in either phase, or in both phases simultaneously. The contaminant partitions between phases with an equilibrium distribution given by Henry`s Law or via kinetic mass transfer. The transport equations are solved using a Galerkin finite element method with reduced integration to lump the resultant matrices. The numerical modelmore »« less
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