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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A 1.1 MegaCuri and 3.5 kilowatt waste source has been buried 30 meters down an auger hole in a tuffaceous alluvium for over three years. Temperature and moisture have been monitored in the surrounding soil during this time and two gaseous tracer migration studies conducted to determine flow parameters. Temperatures exceeding 300°C have been recorded and the moisture range has increased from 10 to 12% to 2 to 14%. The tracer migration data is being analyzed. A two-dimensional transient multi-phase and E.P.A. accepted model, WAFE, is being used to simulate this data and make long term performance projections. Many problems associated with precession, array boundaries and local subroutines have been encountered in converting the model which was developed on the Los Alamos National Laboratory's CRAY based computer system to run on a DEC/VAX 750. Documentation, which is still in rough draft, has also made the valid modification of the code or organization of an input data file difficult. 10 figs.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A 1.1 MegaCuri and 3.5 kilowatt waste source has been buried 30 meters down an auger hole in a tuffaceous alluvium for over three years. Temperature and moisture have been monitored in the surrounding soil during this time and two gaseous tracer migration studies conducted to determine flow parameters. Temperatures exceeding 300°C have been recorded and the moisture range has increased from 10 to 12% to 2 to 14%. The tracer migration data is being analyzed. A two-dimensional transient multi-phase and E.P.A. accepted model, WAFE, is being used to simulate this data and make long term performance projections. Many problems associated with precession, array boundaries and local subroutines have been encountered in converting the model which was developed on the Los Alamos National Laboratory's CRAY based computer system to run on a DEC/VAX 750. Documentation, which is still in rough draft, has also made the valid modification of the code or organization of an input data file difficult. 10 figs.
Author: Publisher: ISBN: Category : Languages : en Pages : 11
Book Description
A small amount of transuranic (TRU) waste has been disposed of at the Greater Confinement Disposal (GCD) site located on the Nevada Test Site's (NTS) Radioactive Waste Management Site (RWMS). The waste has been buried in several deep (37 m) boreholes dug into the floor of an alluvial basin. For the waste to remain in its current configuration, the DOE must demonstrate compliance of the site with the TRU disposal requirements, 40 CFR 191. Sandia's approach to process modelling in performance assessment is to use demonstrably conservative models of the site. Choosing the most conservative model, however, can be uncertain. As an example, diffusion of contaminants upward from the buried waste in the vadose zone water is the primary mechanism of release. This process can be modelled as straight upward planar diffusion or as spherical diffusion in all directions. The former has high fluxes but low release areas, the latter has lower fluxes but is spread over a greater area. We have developed analytic solutions to a simple test problem for both models and compared the total integrated discharges. The spherical diffusion conceptual model results in at least five times greater release to the accessible environment than the planar model at all diffusivities. Modifying the planar model to allow for a larger release, however, compensated for the smaller original planar discharge and resulted in a new planar model that was more conservative that the spherical model except at low diffusivities.
Author: Publisher: ISBN: Category : Languages : en Pages : 120
Book Description
Currently, there are several Greater Confinement Disposal (GCD) boreholes at the Radioactive Waste Management Site (RWMS) for the Nevada Test Site. These are intermediate-depth boreholes used for the disposal of special case wastes, that is, radioactive waste within the Department of Energy complex that do not meet the criteria established for disposal of high-level waste, transuranic waste, or low-level waste. A performance assessment is needed to evaluate the safety of the GCD site, and to examine the feasibility of the GCD disposal concept as a disposal solution for special case wastes in general. This report documents the effort in defining all the waste inventory presently disposed of at the GCD site, and the inventory and release model to be used in a performance assessment for compliance with the Environmental Protection Agency's 40 CFR 191.
Author: Publisher: ISBN: Category : Languages : en Pages : 9
Book Description
The Department of Energy's Nevada Field Office has disposed of a small quantity of high activity and special case wastes using Greater Confinement Disposal facilities in Area 5 of the Nevada Test Site. Because some of these wastes are transuranic radioactive wastes, the Environmental Protection Agency standards for their disposal under 40 CFR Part 191 which requires a compliance assessment. In conducting the 40 CFR Part 191 compliance assessment, review of the Greater Confinement Disposal inventory revealed potentially land disposal restricted hazardous wastes. The regulatory options for disposing of land disposal restricted wastes consist of (1) treatment and monitoring, or (2) developing a no-migration petition. Given that the waste is already buried without treatment, a no-migration petition becomes the primary option. Based on a desire to minimize costs associated with site characterization and performance assessment, a single approach has been developed for assessing compliance with 40 CFR Part 191, DOE Order 5820.2A (which regulates low-level radioactive wastes contained in Greater Confinement Disposal facilities) and developing a no-migration petition. The approach consists of common points of compliance, common time frame for analysis, and common treatment of uncertainty. The procedure calls for conservative bias of modeling assumptions, including model input parameter distributions and adverse processes and events that can occur over the regulatory time frame, coupled with a quantitative treatment of data and parameter uncertainty. This approach provides a basis for a defensible regulatory decision. In addition, the process is iterative between modeling and site characterization activities, where the need for site characterization activities is based on a quantitative definition of the most important and uncertain parameters or assumptions.
Author: Publisher: ISBN: Category : Languages : en Pages : 190
Book Description
The Greater Confinement Disposal (GCD) facility was established in Area 5 at the Nevada Test Site for containment of waste inappropriate for shallow land burial. Some transuranic (TRU) waste has been disposed of at the GCD facility, and compliance of this disposal system with EPA regulation 40 CFR 191 must be evaluated. We have adopted an iterative approach in which performance assessment results guide site data collection, which in turn influences the parameters and models used in performance assessment. The first iteration was based upon readily available data, and indicated that the GCD facility would likely comply with 40 CFR 191 and that the downward flux of water through the vadose zone (recharge) had a major influence on the results. Very large recharge rates, such as might occur under a cooler, wetter climate, could result in noncompliance. A project was initiated to study recharge in Area 5 by use of three environmental tracers. The recharge rate is so small that the nearest groundwater aquifer will not be contaminated in less than 10,000 years. Thus upward liquid diffusion of radionuclides remained as the sole release pathway. This second assessment iteration refined the upward pathway models and updated the parameter distributions based upon new site information. A new plant uptake model was introduced to the upward diffusion pathway; adsorption and erosion were also incorporated into the model. Several modifications were also made to the gas phase radon transport model. Plutonium solubility and sorption coefficient distributions were changed based upon new information, and on-site measurements were used to update the moisture content distributions. The results of the assessment using these models indicate that the GCD facility is likely to comply with all sections of 40 CFR 191 under undisturbed conditions.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The Greater Confinement disposal Test (GCDT) at the Nevada Test Site will be a full scale demonstration of intermediate depth burial for disposal of defense low-level radioactive wastes considered unsuitable for shallow land burial. The GCDT project will demonstrate that these wastes can be efficaciously disposed at a depth of approximately 30 meters where the probability of future inadvertent human intrusion and of potential waste migration are negligible. The GCDT will be instrumented to collect data on properties of the disposal madium (alluvial sediments). Tracers will be injected to assess the transport potential of wastes through the medium. Tracer data will be analyzed to determine the effectiveness of the disposal method.
Author: Laura L. Price Publisher: ISBN: Category : Radioactive waste disposal Languages : en Pages : 31
Book Description
The US Department of Energy (DOE) is responsible for disposing of a variety of radioactive and mixed wastes, some of which are considered special-case waste because they do not currently have a clear disposal option. The DOE's Nevada Field Office contracted with Sandia National Laboratories to investigate the possibility of disposing of some of this special-case waste at the Nevada Test Site (NTS). As part of this investigation, a review of a near-surface and subsurface disposal options that was performed to develop alternative disposal configurations for special-case waste disposal at the NTS. The criteria for the review included (1) configurations appropriate for disposal at the NTS; (2) configurations for disposal of waste at least 100 ft below the ground surface; (3) configurations for which equipment and technology currently exist; and (4) configurations that meet the special requirements imposed by the nature of special-case waste. Four options for subsurface disposal of special-case waste are proposed: mined consolidated rock, mined alluvium, deep pits or trenches, and deep boreholes. Six different methods for near-surface disposal are also presented: earth-covered tumuli, above-grade concrete structures, trenches, below-grade concrete structures, shallow boreholes, and hydrofracture. Greater confinement disposal (GCD) in boreholes at least 100 ft deep, similar to that currently practiced at the GCD facility at the Area 5 Radioactive Waste Management Site at the NTS, was retained as the option that met the criteria for the review. Four borehole disposal configurations are proposed with engineered barriers that range from the native alluvium to a combination of gravel and concrete. The configurations identified will be used for system analysis that will be performed to determine the disposal configurations and wastes that may be suitable candidates for disposal of special-case wastes at the NTS.
Author: Publisher: ISBN: Category : Languages : en Pages : 9
Book Description
The Greater Confinement Disposal (GCD) facility includes four boreholes that contain transuranic (TRLT) waste. Presence of the TRU waste means that this facility must comply with the US Environmental Protection Agency's Environmental Radiation Protection Standards for Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Waste-Final Rule 40 CFR Part 191. To comply with the Containment Requirements of this rule, all potentially disruptive events and processes, and by implication all potentially disruptive combinations of events and processes (scenarios), must be identified for possible inclusion in performance assessments. Screening of the FEPs identified four events for scenario development: exploratory drilling for natural resources, drilling withdrawal wells, irrigation, and subsidence. Recent environmental-isotope analyses of the vadose zone suggest that radionuclide transport from the boreholes to the water table by infiltration is not a feasible transport mechanism within the time frame of regulatory concern. For this reason, the event of drilling withdrawal wells was merged with exploratory drilling for resources. The descriptions of the remaining three events were modified slightly to aid in estimation of event probabilities and consequence analyses. The three events are: exploratory drilling for resources penetrates a TRU borehole, irrigation occurs at the Radioactive Waste Management Site (RWMS), and subsidence occurs at the RWMS. Use of a logic diagram with these three events resulted in the construction of eight scenarios, including base-case (undisturbed) conditions. Screening these scenarios at this stage of scenario development was beyond the scope of this task. Based on the implementation assumptions, this scenario-development procedure produced a comprehensive set of mutually exclusive scenarios that are reproducible and auditable for use in GCD performance assessments.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The Greater Confinement Disposal Test (GCDT) was conducted at the Nevada Test Site to demonstrate an alternative method for management of high-specific-activity (HSA) low-level waste (LLW). The GCDT was initially conceived as a method for managing small volumes of highly concentrated tritium wastes, which, due to their environmental mobiilty, are considered unsuitable for routine shallow land disposal. Later, the scope of the GCDT was increased to address a variety of other "problem" HSA wastes including isotope sources and thermal generating wastes. The basic design for the GCDT evolved from a series of studies and assessments. Operational design objectives were to (1) emplace the wastes at a depth sufficient to minimize or eliminate routine environmental transport mechanisms and instrusion scenarios and (2) provide sufficient protection for operations personnel in the handling of HSA sources. To achieve both objectives, a large diameter borehole was selected. The GCDT consisted of a borehole 3 meters (10 feet) in diameter and 36 meters (120 feet) deep, surrounded by nine monitoring holes at varying radii. The GCDT was instrumented for the measurement of temperature, moisture, and soil-gas content. Over one million curies of HSA LLW were emplaced in GCDT. This report reviews the development of the GCDT project and presents analyses of data collected.
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Author: Laura L. Price
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