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Prediction of the migration of radionuclides to the boundary of a shallow land burial trench

Description: A general model which predicts the source term, radionuclide release rate, as a function of water flow, container degradation rate, waste form leach rate, and radionuclide migration rate from a low-level waste shallow land burial treach is being developed. This paper discusses modeling radionuclide migration, one component of the source term. Simulations of radionuclide transport from a generic shallow land burial trench have been performed for a range of water flow rates, dispersivity values, and distribution coefficients. For the modeling assumptions used and the range of parameters tested, the water flow rate plays the major role in redistributing radionuclides within the trench, except in the case of extremely high dispersion. Dispersion was always found to play significant role in determining transport. This was particularly apparent upstream from the source. Sorption decreased the magnitude of the radionuclide concentration and had the apparent effect of reducing the velocity with which the radionuclides were transported. Diffusion was found to be unimportant in determining radionuclide transport. 12 refs., 8 figs., 2 tabs.
Date: January 1, 1988
Creator: Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

CHALLENGES IN SOURCE TERM MODELING OF DECONTAMINATION AND DECOMMISSIONING WASTES.

Description: Development of real-time predictive modeling to identify the dispersion and/or source(s) of airborne weapons of mass destruction including chemical, biological, radiological, and nuclear material in urban environments is needed to improve response to potential releases of these materials via either terrorist or accidental means. These models will also prove useful in defining airborne pollution dispersion in urban environments for pollution management/abatement programs. Predicting gas flow in an urban setting on a scale of less than a few kilometers is a complicated and challenging task due to the irregular flow paths that occur along streets and alleys and around buildings of different sizes and shapes, i.e., ''urban canyons''. In addition, air exchange between the outside and buildings and subway areas further complicate the situation. Transport models that are used to predict dispersion of WMD/CBRN materials or to back track the source of the release require high-density data and need defensible parameterizations of urban processes. Errors in the data or any of the parameter inputs or assumptions will lead to misidentification of the airborne spread or source release location(s). The need for these models to provide output in a real-time fashion if they are to be useful for emergency response provides another challenge. To improve the ability of New York City's (NYC's) emergency management teams and first response personnel to protect the public during releases of hazardous materials, the New York City Urban Dispersion Program (UDP) has been initiated. This is a four year research program being conducted from 2004 through 2007. This paper will discuss ground level and subway Perfluorocarbon tracer (PFT) release studies conducted in New York City. The studies released multiple tracers to study ground level and vertical transport of contaminants. This paper will discuss the results from these tests and how these results can be used for improving ...
Date: August 1, 2006
Creator: SULLIVAN, T.M.
Partner: UNT Libraries Government Documents Department

Modeling status and needs for temperature calculations within spent fuel disposal containers

Description: The Brookhaven National Laboratory (BNL) Waste Materials and Environment Modeling (WMEM) Program has been assigned the task of helping the DOE formulate and certify analytical tools needed to support and/or strengthen the Waste Package Licensing strategy. One objective of the WMEM program is to perform qualitative and quantitative analyses of processes related to the internal waste package environment, e.g., temperature, radiolysis effects, presence of moisture, etc. The primary objective of this report is to present the findings of a literature review of work pertinent to predicting intact waste package internal temperatures under spent fuel isolation conditions. Therefore, it is assumed that a repository scale thermal analysis has been conducted and the exterior temperature of the waste package is known. Thus, the problem reduces to one determined by the waste package and its properties. Secondary objectives of this report are to identify key parameters and methodologies for performing the thermal analysis within intact waste containers, and identify sources of uncertainty in these calculations. 37 refs., 6 figs., 2 tabs.
Date: October 1, 1989
Creator: Sullivan, T.M. & Pescatore, C.
Partner: UNT Libraries Government Documents Department

Potential {sup 14}CO{sub 2} releases from spent fuel containers at Yucca Mountain

Description: The potential release of gaseous {sup 14}CO{sub 2} from small perforations in spent fuel containers has been evaluated as a function of temperature, hole size, effective porosity of corrosion products within the hole, and time, based on the waste package design parameters and environmental conditions described in the Yucca Mountain Site Characterization Report (SCP). The SCP does not specify initial fill gas (argon) pressure and temperature. It is shown that, if significant {sup 14}C oxidation takes place during the initial, inert-gas phase, an incentive exists to initially underpressurize the containers. This will avoid large, spiked releases of gaseous {sup 14}CO{sub 2} and will result in delayed, smaller, and more uniform release rates over time. Therefore larger size perforations could be tolerated while meeting the applicable regulations. 16 refs., 2 figs., 3 tabs.
Date: March 1, 1991
Creator: Pescatore, C. & Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

DUSTMS-D: DISPOSAL UNIT SOURCE TERM - MULTIPLE SPECIES - DISTRIBUTED FAILURE DATA INPUT GUIDE.

Description: Performance assessment of a low-level waste (LLW) disposal facility begins with an estimation of the rate at which radionuclides migrate out of the facility (i.e., the source term). The focus of this work is to develop a methodology for calculating the source term. In general, the source term is influenced by the radionuclide inventory, the wasteforms and containers used to dispose of the inventory, and the physical processes that lead to release from the facility (fluid flow, container degradation, wasteform leaching, and radionuclide transport). Many of these physical processes are influenced by the design of the disposal facility (e.g., how the engineered barriers control infiltration of water). The complexity of the problem and the absence of appropriate data prevent development of an entirely mechanistic representation of radionuclide release from a disposal facility. Typically, a number of assumptions, based on knowledge of the disposal system, are used to simplify the problem. This has been done and the resulting models have been incorporated into the computer code DUST-MS (Disposal Unit Source Term-Multiple Species). The DUST-MS computer code is designed to model water flow, container degradation, release of contaminants from the wasteform to the contacting solution and transport through the subsurface media. Water flow through the facility over time is modeled using tabular input. Container degradation models include three types of failure rates: (a) instantaneous (all containers in a control volume fail at once), (b) uniformly distributed failures (containers fail at a linear rate between a specified starting and ending time), and (c) gaussian failure rates (containers fail at a rate determined by a mean failure time, standard deviation and gaussian distribution). Wasteform release models include four release mechanisms: (a) rinse with partitioning (inventory is released instantly upon container failure subject to equilibrium partitioning (sorption) with the waste form), (b) diffusion release.(release from ...
Date: January 1, 2006
Creator: SULLIVAN, T.M.
Partner: UNT Libraries Government Documents Department

Investigation of the pitting corrosion of low carbon steel containers

Description: The present study was undertaken because the prediction of the degradation rate of low carbon steel containers over long time frames is one of the crucial elements in the development of a source term model for low-level shallow land burial. The principal data base considered is that of the NBS corrosion measurements of ferrous materials buried in the ground for periods of up to 18 years. The maximum penetration in mils, h/sub m/, due to pitting corrosion was found to conform closely to the relation h/sub m/=kt/sup n/ where t is the exposure time of the sample in years, k is the pitting parameter in mils(years)/sup n/, and n > 0 is a parameter related to the aeration property of the soil. The central objective of the present investigation is the determination of the dependence of the pitting parameters k and n on the soil properties. The result of a detailed linear correlation analysis of k on one hand, and the pH value and the resistivity of the soil on the other hand revealed that k is principally influenced by the pH value of the soil. The resistivity of the soil is found to play a minor role. Based on a linear regression analysis, the following two relationships were derived: k/sub a/ = 5.74 (9.9-pH) and k/sub b/ = 5.05 (2pH-10.3) for acidic and alkaline soils, respectively. The two linear relationships intersect at a point specified by pH = 6.9 and k = 17.3. 8 refs., 3 figs., 1 tab.
Date: January 1, 1988
Creator: Mughabghab, S.F. & Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

BLT (Breach, Leach, and Transport): A source term computer code for low-level waste shallow land burial

Description: This paper discusses the development of a source term model for low-level waste shallow land burial facilities and separates the problem into four individual compartments. These are water flow, corrosion and subsequent breaching of containers, leaching of the waste forms, and solute transport. For the first and the last compartments, we adopted the existing codes, FEMWATER and FEMWASTE, respectively. We wrote two new modules for the other two compartments in the form of two separate Fortran subroutines -- BREACH and LEACH. They were incorporated into a modified version of the transport code FEMWASTE. The resultant code, which contains all three modules of container breaching, waste form leaching, and solute transport, was renamed BLT (for Breach, Leach, and Transport). This paper summarizes the overall program structure and logistics, and presents two examples from the results of verification and sensitivity tests. 6 refs., 7 figs., 1 tab.
Date: January 1, 1990
Creator: Suen, C.J. & Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

Low-level waste shallow land burial source term container breach and waste form leaching model development

Description: A general computer model has been developed to predict the release and transport of radionuclides from shallow land burial facilities. This model predicts the processes of unsaturated water flow, metallic container degradation, leaching of radionuclides from the waste form, and their movement away from the waste form. This paper discusses model development work for the container degradation and leaching aspects of the source term model. Application of these models and the sensitivity of release rates to model parameters, e.g., diffusion coefficients, corrosion rates, etc., are also discussed. 14 refs., 2 figs.
Date: January 1, 1990
Creator: Sullivan, T.M. & Suen, C.J.
Partner: UNT Libraries Government Documents Department

Release of radon contaminants from Yucca Mountain: The role of buoyancy driven flow

Description: The potential for the repository heat source to promote buoyancy driven flow and thereby cause release of radon gas out of Yucca Mountain has been examined through a critical review of the theoretical and experimental studies of this process. The review indicates that steady-state buoyancy enhanced release of natural radon and other contaminant gases should not be a major concern at Yucca Mountain. Barometric pumping and wind pumping are identified as two processes that will have a potentially greater effect on surface releases of gases.
Date: February 1, 1994
Creator: Sullivan, T.M. & Pescatore, C.
Partner: UNT Libraries Government Documents Department

Overview of research and development in subsurface fate and transport modeling

Description: The US Department of Energy is responsible for the remediation of over 450 different subsurface-contaminated sites. Contaminant plumes at these sites range in volume from several to millions of cubic yards. The concentration of contaminants also ranges over several orders of magnitude. Contaminants include hazardous wastes such as heavy metals and organic chemicals, radioactive waste including tritium, uranium, and thorium, and mixed waste, which is a combination of hazardous and radioactive wastes. The physical form of the contaminants includes solutes, nonaqueous phase liquids (NAPLs), and vapor phase contaminants such as volatilized organic chemicals and radon. The subject of contaminant fate and transport modeling is multi-disciplinary, involving hydrology, geology, microbiology, chemistry, applied mathematics, computer science, and other areas of expertise. It is an issue of great significance in the United States and around the world. As such, many organizations have substantial programs in this area. In gathering data to prepare this report, a survey was performed of research and development work that is funded by US government agencies to improve the understanding and mechanistic modeling of processes that control contaminant movement through subsurface systems. Government agencies which fund programs that contain fate and transport modeling components include the Environmental Protection Agency, Nuclear Regulatory Commission, Department of Agriculture, Department of Energy, National Science Foundation, Department of Defense, United States Geological Survey, and National Institutes of Health.
Date: May 1, 1995
Creator: Sullivan, T.M. & Chehata, M.
Partner: UNT Libraries Government Documents Department

Potential increases in natural radon emissions due to heating of the Yucca Mountain rock mass

Description: Heating of the rock mass by the spent fuel in the proposed repository at Yucca Mountain will cause extra amounts of natural radon to diffuse into the fracture system and to migrate faster to the accessible environment. Indeed, free-convection currents due to heating will act to shorten the radon travel times and will cause larger releases than would be possible under undistributed conditions. To estimate the amount of additional radon released due to heating of the Yucca Mountain rock mass, we obtain an expression for the release enhancement factor, E. This factor is defined as the ratio between the total flux of radon at the surface of the mountain before and after closure of the repository assuming the only cause of disturbance to be the heating of the rock mass. With appropriate approximations and using a heat load representative of that expected at Yucca Mountain, the present calculations indicate that the average enhancement factor over the first 10,000 years will be 4.5 as a minimum. These calculations are based on the assumption that barometric pumping does not significantly influence radon release. The latter assumption will need to be substantiated.
Date: February 1, 1992
Creator: Pescatore, C. & Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

Zircaloy cladding performance under spent fuel disposal conditions; Progress report, May 1--October 31, 1989

Description: The Brookhaven National Laboratory (BNL) Waste Materials and Environment Modeling (WMEM) Program has been assigned the task of helping the DOE formulate and certify analytical tools needed to support and/or strengthen the Waste Package Licensing Strategy. One objective of the WMEM program is to perform qualitative and quantitative analyses of irradiated Zircaloy cladding. This progress report presents the early findings of an on-going literature evaluation and the results of the numerical implementation of two models of Zircaloy creep. The report only addresses cladding degradation modes within intact, dry waste containers. Additional degradation modes will be considered when the study is expanded to include moist environments and partly failed containers. Further updates of the present analyses will also be provided.
Date: April 1, 1990
Creator: Pescatore, C.; Cowgill, M.G. & Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

Development of DUST: A computer code that calculates release rates from a LLW disposal unit

Description: Performance assessment of a Low-Level Waste (LLW) disposal facility begins with an estimation of the rate at which radionuclides migrate out of the facility (i.e., the disposal unit source term). The major physical processes that influence the source term are water flow, container degradation, waste form leaching, and radionuclide transport. A computer code, DUST (Disposal Unit Source Term) has been developed which incorporates these processes in a unified manner. The DUST code improves upon existing codes as it has the capability to model multiple container failure times, multiple waste form release properties, and radionuclide specific transport properties. Verification studies performed on the code are discussed.
Date: January 1, 1992
Creator: Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

Modeling of gaseous sup 14 CO sub 2 release from perforations in spent fuel disposal containers

Description: The potential release of gaseous {sup 14}CO{sub 2} from small perforations in spent fuel containers has been evaluated as a function of temperature, hole size, effective porosity of corrosion products within the hole, and time, based on the waste package design parameters and environmental conditions described in the Yucca Mountain Site Characterization Report (SCP). The SCP does not specify initial fill gas (argon) pressure and temperature. It is shown that, if significant {sup 14}C oxidation takes place during the initial, inert-gas phase, an incentive exists to initially underpressurize the containers. This will avoid large, spiked releases of gaseous {sup 14}CO{sub 2} and will result in delayed, smaller, and more uniform release rates over time. Therefore, larger size perforations could be tolerated while meeting the applicable regulations.
Date: November 1, 1991
Creator: Pescatore, C. & Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

Review of the EPA's radionuclide release analyses from LLW disposal trenches used in support of proposed dose limits in 40 CFR 193

Description: The April 1989 draft EPA standard for low-level waste (LLW) disposal, 40 CFR 193, would require disposal site performance to satisfy very stringent dose-limit criteria. The EPA suggests that these limits can be achieved by relying extensively on waste solidification before disposal. The EPA justifies the achievability of the proposed criteria based on performance assessment analyses in the general context of trench burial of the LLW. The core models implemented in those analyses are codified in the EPA's PRESTO family of codes. Because a key set of models for predicting potential releases are the leach-and-transport models from a disposal trench, these have been reviewed for completeness and applicability to trench disposal methods. The overall conclusion of this review is that the generic analyses performed by the EPA are not sufficiently comprehensive to support the proposed version of 40 CFR 193. More rigorous analyses may find the draft standard criteria to be unattainable.
Date: November 1, 1991
Creator: Pescatore, C. & Sullivan, T.M.
Partner: UNT Libraries Government Documents Department

Development of DUST: A computer code that calculates release rates from a LLW disposal unit

Description: Performance assessment of a Low-Level Waste (LLW) disposal facility begins with an estimation of the rate at which radionuclides migrate out of the facility (i.e., the disposal unit source term). The major physical processes that influence the source term are water flow, container degradation, waste form leaching, and radionuclide transport. A computer code, DUST (Disposal Unit Source Term) has been developed which incorporates these processes in a unified manner. The DUST code improves upon existing codes as it has the capability to model multiple container failure times, multiple waste form release properties, and radionuclide specific transport properties. Verification studies performed on the code are discussed.
Date: April 1, 1992
Creator: Sullivan, T. M.
Partner: UNT Libraries Government Documents Department

Modeling of gaseous {sup 14}CO{sub 2} release from perforations in spent fuel disposal containers

Description: The potential release of gaseous {sup 14}CO{sub 2} from small perforations in spent fuel containers has been evaluated as a function of temperature, hole size, effective porosity of corrosion products within the hole, and time, based on the waste package design parameters and environmental conditions described in the Yucca Mountain Site Characterization Report (SCP). The SCP does not specify initial fill gas (argon) pressure and temperature. It is shown that, if significant {sup 14}C oxidation takes place during the initial, inert-gas phase, an incentive exists to initially underpressurize the containers. This will avoid large, spiked releases of gaseous {sup 14}CO{sub 2} and will result in delayed, smaller, and more uniform release rates over time. Therefore, larger size perforations could be tolerated while meeting the applicable regulations.
Date: November 1, 1991
Creator: Pescatore, C. & Sullivan, T. M.
Partner: UNT Libraries Government Documents Department

Review of the EPA`s radionuclide release analyses from LLW disposal trenches used in support of proposed dose limits in 40 CFR 193

Description: The April 1989 draft EPA standard for low-level waste (LLW) disposal, 40 CFR 193, would require disposal site performance to satisfy very stringent dose-limit criteria. The EPA suggests that these limits can be achieved by relying extensively on waste solidification before disposal. The EPA justifies the achievability of the proposed criteria based on performance assessment analyses in the general context of trench burial of the LLW. The core models implemented in those analyses are codified in the EPA`s PRESTO family of codes. Because a key set of models for predicting potential releases are the leach-and-transport models from a disposal trench, these have been reviewed for completeness and applicability to trench disposal methods. The overall conclusion of this review is that the generic analyses performed by the EPA are not sufficiently comprehensive to support the proposed version of 40 CFR 193. More rigorous analyses may find the draft standard criteria to be unattainable.
Date: November 1, 1991
Creator: Pescatore, C. & Sullivan, T. M.
Partner: UNT Libraries Government Documents Department

PERFLUOROCARBON GAS TRACER STUDIES TO SUPPORT RISK ASSESSMENT MODELING OF CRITICAL INFRASTRUCTURE SUBJECTED TO TERRORIST ATTACKS.

Description: Development of real-time predictive modeling to identify the dispersion and/or source(s) of airborne weapons of mass destruction including chemical, biological, radiological, and nuclear material in urban environments is needed to improve response to potential releases of these materials via either terrorist or accidental means. These models will also prove useful in defining airborne pollution dispersion in urban environments for pollution management/abatement programs. Predicting gas flow in an urban setting on a scale of less than a few kilometers is a complicated and challenging task due to the irregular flow paths that occur along streets and alleys and around buildings of different sizes and shapes, i.e., ''urban canyons''. In addition, air exchange between the outside and buildings and subway areas further complicate the situation. Transport models that are used to predict dispersion of WMD/CBRN materials or to back track the source of the release require high-density data and need defensible parameterizations of urban processes. Errors in the data or any of the parameter inputs or assumptions will lead to misidentification of the airborne spread or source release location(s). The need for these models to provide output in a real-time fashion if they are to be useful for emergency response provides another challenge. To improve the ability of New York City's (NYC's) emergency management teams and first response personnel to protect the public during releases of hazardous materials, the New York City Urban Dispersion Program (UDP) has been initiated. This is a four year research program being conducted from 2004 through 2007. This paper will discuss ground level and subway Perfluorocarbon tracer (PFT) release studies conducted in New York City. The studies released multiple tracers to study ground level and vertical transport of contaminants. This paper will discuss the results from these tests and how these results can be used for improving ...
Date: May 6, 2006
Creator: SULLIVAN, T.M.; HEISER, J.; WATSON, T.; ALLWINE, K.J. & FLAHERTY, J.E.
Partner: UNT Libraries Government Documents Department

THE COMPETITION BETWEEN METHYLMERCURY RISKS AND OMEGA-3 POLYUNSATURATED FATTY ACID BENEFITS: A REVIEW OF CONFLICTING EVIDENCE ON FISH CONSUMPTION AND CARDIOVASCULAR HEALTH.

Description: The health concerns of methylmercury (MeHg) contamination of seafood have recently been extended to include cardiovascular effects, especially premature mortality. Although the fatty acids (fish oils) found in most species are thought to confer a wide range of health benefits, especially to the cardiovascular system, some epidemiological studies have suggested that such benefits may be offset by adverse effects of MeHg. This comprehensive review is based on searches of the NIH MEDLINE database and compares and contrasts 145 published studies involving cardiovascular effects and exposures to mercury and other fish contaminants, intake of fatty acids including dietary supplements of fish oils, and rates of seafood consumption. Since few of these studies include adequate simultaneous measurements of all of these potential predictor variables, we summarized their effects separately, across the available studies of each, and then drew conclusions based on the aggregated findings. It is important to realize that studies of seafood consumption encompass the net effects of all of these predictor variables, but that seafood intake studies are rarely supported by human biomarker measurements that reflect the actual uptake of harmful as well as beneficial fish ingredients. As a result, exposure measurement error is an issue when comparing studies and predictor variables. It is also possible that the observed benefits of eating fish may relate more to the characteristics of the consumers than to those of the fish. We found the evidence for adverse cardiovascular effects of MeHg to be sparse and unconvincing. Studies of cardiovascular mortality show net benefits, and the findings of adverse effects are mainly limited to studies Finland at high mercury exposure levels. By contrast, a very consistent picture of beneficial effects is seen for fatty acids, after recognizing the effects of exposure uncertainties and the presence of threshold effects. Studies based on measured biomarker levels ...
Date: October 31, 2006
Creator: LIPFERT, F.W. & SULLIVAN, T.M.
Partner: UNT Libraries Government Documents Department

FISH CONSUMPTION, METHYLMERCURY, AND HUMAN HEART DISEASE.

Description: Environmental mercury continues to be of concern to public health advocates, both in the U.S. and abroad, and new research continues to be published. A recent analysis of potential health benefits of reduced mercury emissions has opened a new area of public health concern: adverse effects on the cardiovascular system, which could account for the bulk of the potential economic benefits. The authors were careful to include caveats about the uncertainties of such impacts, but they cited only a fraction of the applicable health effects literature. That literature includes studies of the potentially harmful ingredient (methylmercury, MeHg) in fish, as well as of a beneficial ingredient, omega-3 fatty acids or ''fish oils''. The U.S. Food and Drug Administration (FDA) recently certified that some of these fat compounds that are primarily found in fish ''may be beneficial in reducing coronary heart disease''. This paper briefly summarizes and categorizes the extensive literature on both adverse and beneficial links between fish consumption and cardiovascular health, which are typically based on studies of selected groups of individuals (cohorts). Such studies tend to comprise the ''gold standard'' of epidemiology, but cohorts tend to exhibit a great deal of variability, in part because of the limited numbers of individuals involved and in part because of interactions with other dietary and lifestyle considerations. Note that eating fish will involve exposure to both the beneficial effects of fatty acids and the potentially harmful effects of contaminants like Hg or PCBs, all of which depend on the type of fish but tend to be correlated within a population. As a group, the cohort studies show that eating fish tends to reduce mortality, especially due to heart disease, for consumption rates up to about twice weekly, above which the benefits tend to level off. A Finnish cohort study showed increased ...
Date: September 21, 2005
Creator: LIPFERT, F.W. & SULLIVAN, T.M.
Partner: UNT Libraries Government Documents Department

The New York Midtown Dispersion Study (Mid-05) Meteorological Data Report.

Description: The New York City midtown dispersion program, MID05, examined atmospheric transport in the deep urban canyons near Rockefeller Center. Little is known about air flow and hazardous gas dispersion under such conditions, since previous urban field experiments have focused on small to medium sized cities with much smaller street canyons and examined response over a much larger area. During August, 2005, a series of six gas tracer tests were conducted and sampling was conducted over a 2 km grid. A critical component of understanding gas movement in these studies is detailed wind and meteorological information in the study zone. To support data interpretation and modeling, several meteorological stations were installed at street level and on roof tops in Manhattan. In addition, meteorological data from airports and other weather instrumentation around New York City were collected. This document describes the meteorological component of the project and provides an outline of data file formats for the different instruments. These data provide enough detail to support highly-resolved computational simulations of gas transport in the study zone.
Date: January 1, 2007
Creator: Reynolds, R. M.; Sullivan, T. M.; Smith, S. & Cassella, V.
Partner: UNT Libraries Government Documents Department

BLT-EC (Breach, Leach and Transport-Equilibrium Chemistry) data input guide. A computer model for simulating release and coupled geochemical transport of contaminants from a subsurface disposal facility

Description: The BLT-EC computer code has been developed, implemented, and tested. BLT-EC is a two-dimensional finite element computer code capable of simulating the time-dependent release and reactive transport of aqueous phase species in a subsurface soil system. BLT-EC contains models to simulate the processes (container degradation, waste-form performance, transport, chemical reactions, and radioactive production and decay) most relevant to estimating the release and transport of contaminants from a subsurface disposal system. Water flow is provided through tabular input or auxiliary files. Container degradation considers localized failure due to pitting corrosion and general failure due to uniform surface degradation processes. Waste-form performance considers release to be limited by one of four mechanisms: rinse with partitioning, diffusion, uniform surface degradation, and solubility. Transport considers the processes of advection, dispersion, diffusion, chemical reaction, radioactive production and decay, and sources (waste form releases). Chemical reactions accounted for include complexation, sorption, dissolution-precipitation, oxidation-reduction, and ion exchange. Radioactive production and decay in the waste form is simulated. To improve the usefulness of BLT-EC, a pre-processor, ECIN, which assists in the creation of chemistry input files, and a post-processor, BLTPLOT, which provides a visual display of the data have been developed. BLT-EC also includes an extensive database of thermodynamic data that is also accessible to ECIN. This document reviews the models implemented in BLT-EC and serves as a guide to creating input files and applying BLT-EC.
Date: May 1997
Creator: MacKinnon, R. J.; Sullivan, T. M. & Kinsey, R. R.
Partner: UNT Libraries Government Documents Department

Development of a general model to predict the rate of radionuclide release (source term) from a low-level waste shallow land burial facility

Description: Federal Code of Regulations 10 CFR 61 requires that any near surface disposal site be capable of being characterized, analyzed, and modeled. The objective of this program is to assist NRC in developing the ability to model a disposal site that conforms to these regulations. In particular, a general computer model capable of predicting the quantity and rate of radionuclide release from a shallow land burial trench, i.e., the source term, is being developed. The framework for this general model has been developed and consists of four basic compartments that represent the major processes that influence release. These compartments are: water flow, container degradation, release from the waste packages, and radionuclide transport. Models for water flow and radionuclide transport rely on the use of the computer codes FEMWATER and FEMWASTE. These codes are generally regarded as being state-of-the-art and required little modification for their application to this project. Models for container degradation and release from waste packages have been specifically developed for this project. This paper provides a brief description of the models being used in the source term project and examples of their use over a range of potential conditions. 13 refs.
Date: January 1, 1988
Creator: Sullivan, T.M.; Kempf, C.R.; Suen, C.J. & Mughabghab, S.M.
Partner: UNT Libraries Government Documents Department