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Internal Technical Report, Safety Analysis Report 5 MW(e) Raft River Research and Development Plant

Description: The Raft River Geothermal Site is located in Southern Idaho's Raft River Valley, southwest of Malta, Idaho, in Cassia County. EG and G idaho, Inc., is the DOE's prime contractor for development of the Raft River geothermal field. Contract work has been progressing for several years towards creating a fully integrated utilization of geothermal water. Developmental progress has resulted in the drilling of seven major DOE wells. Four are producing geothermal water from reservoir temperatures measured to approximately 149 C (approximately 300 F). Closed-in well head pressures range from 69 to 102 kPa (100 to 175 psi). Two wells are scheduled for geothermal cold 60 C (140 F) water reinjection. The prime development effort is for a power plant designed to generate electricity using the heat from the geothermal hot water. The plant is designated as the ''5 MW(e) Raft River Research and Development Plant'' project. General site management assigned to EG and G has resulted in planning and development of many parts of the 5 MW program. Support and development activities have included: (1) engineering design, procurement, and construction support; (2) fluid supply and injection facilities, their study, and control; (3) development and installation of transfer piping systems for geothermal water collection and disposal by injection; and (4) heat exchanger fouling tests.
Date: November 17, 1981
Creator: Brown, E.S.; Homer, G.B.; Shaber, C.R. & Thurow, T.L.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Software Requirements and Design Guide for the 5MW(e) Raft River Pilot Plant

Description: The 5MW(e) electrical generating plant is a demonstrational unit intended to provide engineering data basic to improvement of geothermal-electric technology. It is anticipated that the plant will operate on a production basis after initial testing, and that periodic re-testing will be done to measure the effects of fouling in heat exchanges and aging generally. The initial tests will confirm engineering estimates of performance, and will identify optimum feasible operatinq conditions and maximum power generating capacity. They will also identify any anomalous plant behavior not foreseen. Several tests will lead to quantification of constant and variable terms used in thermodynamic relationships descriptive of plant and subsystem behavior. Because the product of the testing will be confirmatory engineering data heretofore unavailable, the plant has been carefully instrumented, with either explicit or implicit instrumentation redundancy for most parameters to be measured. The 5MW(e) data system collects the data directly from the instrumentation. Enhancements such as on-line analytical routines may be added later, but initially, data capture shall be the sole activity of the data system. The 5MW(e) plant converts the energy of geothermally heated water to electrical energy conforming to 60 Hz commercial power standards. The plant capacity is sufficiently large to be useful in a demonstrational sense, but is limited to a capacity conservative of the geothermal energy resource, which hasn't been fully explored. The 5MW(e) plant will continue on a regular production basis after completion of the testing. Additional production units may be added at a later time.
Date: May 15, 1980
Creator: Metcalf, D.D. & Cole, M.S.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Summary of Raft River Supply and Injection System Operational History

Description: Asbestos-cement (Transite) pipe was installed at the Raft River Geothermal Area in the fall of 1975 and has been used extensively since. The pipe is used to transfer water from the well sites to the testing areas, reserve pits, and reinjection wells. The pipeline was designed to transport approximately 300 F water at 150 psi over a period of time for the present testing program and later, for the 5 MW(e) Raft River Pilot Plant. Numerous line failures have occurred since the original lines were installed. Due to the various causes of the line failures and the extensive downtime which has occurred because of them, further examination of Transite pipe is necessary to determine its future use as completion of the 5 MW(e) pilot plant approaches. The Conversion Technology and Engineering Branch has completed a preliminary study of the effects of S&I system transients on Transite pipe (re: OJD-7-79). Recommendations are proposed to conduct further studies and tests; however, no funding is presently available due to limitations in the budget for the 5 MW(e) pilot plant project. The Mechanical Design Branch is continuing design analysis in an effort to gather information to determine maximum warmup rates for the S&I system.
Date: January 1, 1980
Creator: Walrath, L.F.
Partner: UNT Libraries Government Documents Department

Long-Term Stewardship of Mixed Wastes: Passive Reactive Barriers for Simultaneous In Situ Remediation of Chlorinated Solvent, Heavy Metal, and Radionuclide Contaminants

Description: The collaborative project was designed to evaluate the possibility developing a subsurface remediation technology for mixed wastes at Department of Energy sites using a group of common soil bacteria of the genus Cellulomonas. We have been gaining a better understanding of microbial transformation of chromium, uranium, iron minerals, and trinitrotoluene (TNT) by Cellulomonas spp. in simulated subsurface environments.
Date: June 1, 2005
Creator: Gerlach, Robin; Cunningham, Al & Peyton, Brent
Partner: UNT Libraries Government Documents Department

Mobility of Source Zone Heavy Metals and Radionuclides: The Mixed Roles of Fermentative Activity on Fate and Transport of U and Cr

Description: Predicting the potential migration of metals and radionuclides from waste pits and trenches will require understanding the effects of carbon and electron flow through these environments. Important aspects of this flow include the physiological activity of cellulolytic and non-cellulolytic fermentative microbial populations, as well as the subsequent activity of metal and radionuclide reducing bacteria. The activity of subsurface fermentative microbial populations is significantly understudied even though these organisms can affect contaminant migration by at least two mechanisms. In the first mechanism, products of the fermentation process can act as chelators for metals and radionuclides increasing their transport through underlying geological media. The second mechanism is the reduction and immobilization of metals and radionuclides since some fermentative bacteria have been shown to directly reduce metals and radionuclides, while their fermentation products can provide carbon and energy for respiratory metal reducing bacteria that can also reduce oxidized metals and radionuclides.
Date: June 1, 2006
Creator: Apel, William; Peyton, Brent; Gerlach, Robin & Lee, Brady
Partner: UNT Libraries Government Documents Department

Molecular Mechanisms of Scale Deposition

Description: Scales do not develop equally on different substrates, even when bulk physicochemical conditions are the same. The reason for these differential developments, one must presume, are due to subtle features of the near-surface region, either composition or structure. They intend to focus their studies on the structural aspects, including concerns about the molecular structures of solvated components that may be involved with the surface reactions. This approach is richly mechanistic in outlook. It involves concepts of stereo constraints on the chemical processes by which solutes exchange atoms or electrons with substrates. These constraints are a consequence of the more or less regular pattern of electropotential that exists at a crystalline surface. In principle, the electropotential pattern can be manipulated either through the substrate (more precisely by selecting or designing substrates that have desirable patterns) or through the components in the near-surface liquid which modify the basic substrate-induced patterns there.
Date: January 1, 1976
Creator: Michels, Donald E. & Keiser, Dennis D.
Partner: UNT Libraries Government Documents Department

Properties of Geopressured Brines and Wells in the Gulf Coast and Opportunities for Industrial/Research Participation

Description: Geopressured reservoirs exhibit pressure gradients in excess of the normal hydrostatic gradient. In the Gulf Coast area the normal gradient is 0.465 psi/ft. Pressures may approach lithostatic pressure and have been measured as high as 1.05 psi/ft in the Gulf Coast area. Geopressured basins exist worldwide and in a number of U.S. locations, east, west, north and south. The Gulf Coast area has been studied extensively and is the subject of the DOE geopressured-geothermal research at present. The assumed ranges in resource characteristics include: depth from -12,000 to > -20,000 feet, brine flow rate from 20,000 to 40,000 bpd, temperature from 300 to 400 F, bottomhole pressure from 12,000 to 18,500 psi; salinity from 20,000 to 200,000 mg/L, gas-water ratio from 40 to 80 scf/bbl., and condensate from a trace to production. Energy in the geopressured resource includes gas, thermal, and hydraulic energy. It has been estimated that there are 6,000 quads of methane and 11,000 quads of thermal energy in the Gulf Coast area geopressured-geothermal reservoirs. Estimates run as high as 50,000 quad for the thermal energy (Wallace et al, 1978). Present industrial interest in the Pleasant Bayou and Hulin wells includes: desalination plants, an economic study by a power company for regional use, use of generated electricity by a coalition of towns, aquaculture (catfish farming) research program, and an unsolicited proposal for enhanced oil recovery of heavy oil. Direct uses of the hot brine cover dozens of industries and processes. An example of multiple uses in the USSR is shown. Outside agency interest includes the U.S.G.S., N.S.F., G.R.I., and possibly other areas within DOE. A research spin-off: a sensitive in-line benzene monitor has been designed by USL and will be tested in the near future. An in-line pH monitor is also under development for the harsh conditions of ...
Date: March 21, 1989
Creator: Wys, J. Nequs- de
Partner: UNT Libraries Government Documents Department

Representative Element Modeling of Fracture Systems Based on Stochastic Analysis

Description: An important task associated with reservoir simulation is the development of a technique to model a large number of fractures with a single description. Representative elements must be developed before reservoir scale simulations can adequately address the effects of intersecting fracture systems on fluid migration. An effective element model will sharply reduce the cost and complexity of large scale simulations to bring these to manageable levels. Stochastic analysis is a powerful tool which can determine the hydraulic and transport characteristics of intersecting sets of statistically defined fractures. Hydraulic and transport characteristics are required to develop representative elements. Given an assumption of fully developed laminar flow, the net fracture conductivities and hence flow velocities can be determined from descriptive statistics of fracture spacing, orientation, aperture, and extent. The distribution of physical characteristics about their means leads to a distribution of the associated conductivities. The variance of hydraulic conductivity induces dispersion into the transport process. The simplest of fracture systems, a single set of parallel fractures, is treated to demonstrate the usefulness of stochastic analysis. Explicit equations for conductivity of an element are developed and the dispersion characteristics are shown. The analysis reveals the dependence of the representative element properties on the various parameters used to describe the fracture system.
Date: January 21, 1986
Creator: Clemo, T.M.
Partner: UNT Libraries Government Documents Department

Research and Development of Information on Geothermal Direct Heat Application Projects

Description: This is the first annual report of ICF's geothermal R&D project for the Department of Energy's Idaho Operations Office. The overall objective of this project is to compile, analyze, and report on data from geothermal direct heat application projects. Ultimately, this research should convey the information developed through DOE's and Program Opportunity Notice (PON) activities as well as through other pioneering geothermal direct heat application projects to audiences which can use the early results in new, independent initiatives. A key audience is potential geothermal investors.
Date: October 1, 1981
Creator: Hederman, William F., Jr. & Cohen, Laura A.
Partner: UNT Libraries Government Documents Department

Reservoir Modeling and Prediction at Pleasant Bayou Geopressured-Geothermal Reservoir

Description: Modeling and prediction of geopressured-geothermal reservoirs is an excellent example of an engineering problem that can be solved through many different means. The problem may be approached from a purely numerical viewpoint, where a successful history match ''demonstrates'' the validity of the reservoir model, or from an analytical point of view. Each method has its own inherent limitations and weaknesses. Such limitations can be minimized by using some combination of both numerical and analytical methods, taking advantage of the strengths of each without the attendant weaknesses. This paper describes a combined numerical/analytical approach to reservoir engineering at the Pleasant Bayou geopressured-geothermal reservoir. A reservoir description had previously been developed, through which a successful history match was performed. Certain details of the reservoir can also be obtained through analysis of pressure and flow transients; these can then be used to constrain the numerical model. Methods for extracting such reservoir data are discussed, and the manner in which they can be used as constraints in the numerical models are presented.
Date: March 24, 1992
Creator: Shook, Mike
Partner: UNT Libraries Government Documents Department

Reservoir Technology

Description: The reservoir technology program supports the utilization of geothermal resources through development and verification of new earth science technologies for: exploration, fluid production and injection; and prediction of reservoir lifetimes. A two-fold strategy of conducting DOE-sponsored research to meet higher-risk, longer-term needs and cost-shared research with industry in areas of greatest current need is utilized to maximize the benefit of the program to the geothermal industry. The program uses a coordinated, multi-disciplinary approach to investigating and solving reservoir problems facing the industry. Research at The Geysers geothermal field has received major emphasis in the past three years. Recent progress in that work will be reviewed in detail by The Geysers operators, federal, state and local regulators and other interested parties during a meeting in Santa Rosa on May 5 and 6, 1992. Hence the papers by Lipman, Bodvarsson et al., Wannamaker, et al., Horne, and Shook in this proceedings volume emphasize non-Geysers research in the program.
Date: March 24, 1992
Creator: Renner, J.L.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, 60 KW Test Facility Heat Exchanger Specification

Description: This report presents the thermal specifications for three heat exchangers (preheater, boiler and condenser) to be used in a 60 kW prototype power plant installed at the Raft River geothermal facility. This prototype plant is unique in that it will utilize a working fluid of 90% propane--10% isopentane (by weight) operating at super-critical pressures in a binary geothermal cycle to extract energy from a 280 F geothermal resource. Studies have shown that this super-critical cycle can provide a net performance about 20% higher than that of the optimum dual-boiling isobutane cycle currently designed for the 5 MW Raft River pilot plant.
Date: August 1, 1981
Creator: Kochan, R.J.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, 1981 Annual Report, An Analysis of the Response of the Raft River Geothermal Site Monitor Wells

Description: A groundwater monitoring program has been established on the Raft River Geothermal Site since 1978. The objective of this program is to document possible impacts that may be caused by geothermal production and injection on the shallow aquifers used for culinary and irrigation purposes. This annual progress report summarizes data from 12 monitor wells during 1981. These data are compared with long-term trends and are correlated with seasonal patterns, irrigation water use and geothermal production and testing. These results provide a basis for predicting long-term impacts of sustained geothermal production and testing. To date, there has been no effect on the water quality of the shallow aquifers.
Date: April 1, 1982
Creator: Thurow, T.L.; Large, R.M.; Allman, D.W.; Tullis, J.A. & Skiba, P.A.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Geothermal Wetland Research Test Plan for FY-1962

Description: Results from the FY-81 research confirmed earlier findings that aquatic plants can accumulate elements from geothermal water. productivity results for cattail and bulrush were promising considering the fact that FY-81 was the first year for the outdoor system, and that the wetland was not planted until June. Objectives of the FY-82 research will be to determine productivity and water purification values for a full growing season. These objectives will be accomplished by: (1) using a mass balance approach to evaluate the movement of chemicals within and through the geothermal wetland system; (2) determining biomass production rates using the permanent reference quadrat (standing crop) technique; (3) determining the effect of retention time on water quality; (4) determining accumulation factors for the plants grown in the geothermal water; and (5) evaluating the algae at Raft River for its potential as a bioaccumulator, biomass producer, and feedstock for energy conversion.
Date: June 1, 1981
Creator: Breckenridge, R.P. & Pryfogle, P.A.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Heat Exchanger Sizing for 20 MW Geothermal Power Plants at MX Sites

Description: This report presents the details of the analyses used to size the heaters, steam condenser, and working fluid condenser for a proposed 20 MW geothermal power plant application at MX sites in the southwest. These units would use a mixture of hydrocarbons (90% isobutane--10% n-hexane) to extract energy from moderate temperature resources (resource temperatures of 365 F, 400 F, and 450 F were considered). The working fluid will be maintained at supercritical pressures in the heater units. Studies have shown that this cycle will provide a significant net power increase over standard dual boiling single fluid cycles currently in use, e.g., the Raft River 5 MW pilot plant.
Date: December 1, 1981
Creator: Kochan, R.J. & Bliem, C.J.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Hydrothermal Injection Program - East Mesa 1983-84 Test Data

Description: This report presents a test data index and a data plots for a series of 12 drawdown and tracer injection-withdrawal tests in porous-media aquifers at the East Mesa Geothermal Field located in the Imperial Valley near El Centro, California. Test and instrumentation summaries are also provided. The first 10 of these tests were completed during July and August 1983. The remaining 2 tests were completed in February 1984, after a 6-month quiescent period, in which tracers were left in the reservoir. The test wells used were 56-30 and 56-19, with 38-30 supplying water for the injection phase and 52-29 used as a disposal well during the backflowing of the test wells. Six other wells in the surrounding area were measured periodically for possible hydrologic effects during testing. It is not the intent of this report to supply analyzed data, but to list the uninterpreted computer stored data available for analysis. The data have been examined only to the extent to ensure that they are reasonable and internally consistent. This data is stored on permanent files at the Idaho National Engineering Laboratory (INEL) Cyber Computer Complex. The main processors for this complex are located at the Computer Science Center (CSC) in Idaho Falls, Idaho. The Hydrothermal Injection Test program, funded by the Department of Energy, was a joint effort between EG and G Idaho, Inc., the University of Utah Research Institute (UURI) and Republic Geothermal, Inc. (RGI) of Santa Fe Springs, California.
Date: September 1, 1984
Creator: Freiburger, R.M.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Low-To-Moderate Temperature Reservoir Engineering Research Program - Fiscal Year 1982

Description: Numerous low (<90 C) to moderate (90 C-150 C) geothermal resources occur in many areas of the United States. The reservoir research conducted at the Idaho National Engineering Laboratory (INEL) is designed to develop innovative techniques that can be used to evaluate reservoir characteristics and improve reservoir management for low-to-moderate temperature resources. The purpose of this report is to review the program accomplishments for FY 1982 and present the initial data and results obtained from the ongoing research program. The project tasks reported in this document are: (1) Low-To-Moderate Temperature Hydrothermal Reservoir Engineering Handbook; and (2) Reservoir Assessment Technique Development--data analysis and reaction kinetics.
Date: September 1, 1982
Creator: Russell, B.F.; Dolenc, M.R.; Downs, W.F. & Hull, L.C.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Management Plan for Fluid Supply and Injection System for the Raft River 5 MW(e) Pilot Power Plant

Description: This report details a plan for developing a fluid supply system for the First 5 MW(e) Pilot Power Plant at Raft River. The pilot plant has been specifically designed to use the medium-temperature geothermal water so common throughout the West. EG and G Idaho, Inc., the Department of Energy Raft River Rural Electric Co-op, the US Geological Survey (USGS) and the State of Idaho have worked together to develop a facility that will use an organic liquid as the working fluid. Four wells have been drilled in the Raft River Valley, about ten miles South of Malta, in southern Idaho. The completed well system will consist of seven wells: two conventional injection wells, three production wells, and a standby reserve well of each type. The additional three wells are to be drilled in FY-1978, in order to complete a coordinated test program before the First Pilot Power Plant is ready for operation. The system has been designed to meet the test-loop pilot plant's basic requirement: a 2450 gpm supply of geothermal fluid, at a nominal temperature of 290 F and with salinity of less than 5000 ppm. Injection of cooled geothermal fluid into the Raft River reservoir will also require a network of monitor wells. The Idaho Department of Water Resources (IDWR), USGS, EG and G Idaho, and the Department of Energy will jointly select sites for two 1500-foot and five 500-foot monitoring wells. This plan considers the work required to complete construction of the fluid supply system and obtain a preliminary check of its performance capability; the plan will discuss project management, costs, schedules, drilling, testing, environmental monitoring, and safety.
Date: January 9, 1978
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Program Plan for Conversion of Biomass to Liquid Fuel Using Geothermal Energy

Description: Due to the decreased supply of petroleum and the large quantity of import oil, there exists sufficient economic justification to develop a biomass-liquid fuel industry. Geothermal energy uniquely fits the biomass production and conversion requirements. To accelerate industrial development of biomass-to-liquid fuel conversion using geothermal energy, a national program is required. Because of the INEL's unique experience in moderate-temperature geothermal applications, they should take the lead in this program. Based on an extensive survey of the biomass conversion field, areas of needed work were identified and a program plan was developed. This plan separates the INEL role into two parts. (1) Commercial Support--Existing technology can be commercially applied to provide a portion of the liquid fuel needs. To accelerate development, INEL needs to provide technical and management support to existing programs such as direct assistance, loan guarantees, PONs, and PRDAs. (2) Technical Development--Application of new geothermal technology in the production and conversion of biomass can increase the quantity of domestically produced liquid fuel. The program plan identifies needed work down to the task level. Three cost account levels are identified: (1) Biomass-to-Liquid Fuel Technology, (2) Biomass-to-Liquid Fuel Advanced Technology Demonstration, and (3) Biomass-to-Liquid Fuel Commercial Support. The end item is an advanced technology demonstration plant with an FY-86 target date. This plant should be built by the private sector through cost sharing, loan guarantees, or the PON program. However, it could be built by a government contractor. Development work will be centered at INEL, but much of the work will be contracted to take advantage of outside expertise and for technology transfer reasons. Other programs, agencies, institutions, and companies are performing and will perform related work. Continued interface is necessary to build national expertise and avoid duplication of effort.
Date: September 10, 1979
Creator: Chaney, R.E.; Jacoby, J.K. & LaRue, D.M.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Raft River Pump Selection Analysis

Description: The following is an analysis investigating the relation between well pumping rates and overall plant power at the 5 MW Raft River geothermal plant No.1. Information is generated to allow selection of well pumping rates, pump setting depths, and required characteristics of supply and injection pumps. The analysis proceeds with a simple analysis of plant power--flow split relationships from which the conclusion is drawn that the plant power, within certain limits, is insensitive to the flow split between wells. A more complex analysis is then performed which examines flow split sensitivity with all four wells operating and sensitivity of plant power to supply flow increases. This analysis is summarized by tentative field flow rate selections and a data table. Tentative supply and injection pump selections are made and contingency pumps are discussed.
Date: June 1, 1979
Creator: Jacoby, J.K. & Bliem, C.J.
Partner: UNT Libraries Government Documents Department

Internal Technical Report, Safety Analysis Report 5 MW(e) Raft River Pilot Plant

Description: The Raft River Geothermal Site is located in Southern Idaho's Raft River Valley, southwest of Malta, Idaho, in Cassia County. EG and G idaho, Inc., is the DOE's prime contractor for development of the Raft River geothermal field. Contract work has been progressing for several years towards creating a fully integrated utilization of geothermal water. Developmental progress has resulted in the drilling of seven major DOE wells. Four are producing geothermal water from reservoir temperatures measured to approximately 149 C (approximately 300 F). Closed-in well head pressures range from 69 to 102 kPa (100 to 175 psi). Two wells are scheduled for geothermal cold 60 C (140 F) water reinjection. The prime development effort is for a power plant designed to generate electricity using the heat from the geothermal hot water. The plant is designated as the ''5 MW(e) Raft River Research and Development Plant'' project. General site management assigned to EG and G has resulted in planning and development of many parts of the 5 MW program. Support and development activities have included: (1) engineering design, procurement, and construction support; (2) fluid supply and injection facilities, their study, and control; (3) development and installation of transfer piping systems for geothermal water collection and disposal by injection; and (4) heat exchanger fouling tests.
Date: May 30, 1980
Creator: Brown, E.S.; Homer, G.B.; Spencer, S.G. & Shaber, C.R.
Partner: UNT Libraries Government Documents Department

ANNUAL REPORT FOR ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 86598 COUPLED FLOW AND REACTIVITY IN VARIABLY SATURATED POROUS MEDIA

Description: Improved models of contaminant migration in heterogeneous, variably saturated porous media are required to better define the long-term stewardship requirements for U.S. Department of Energy (DOE) lands and to assist in the design of effective vadose-zone barriers to contaminant migrations. The objective of our three-year project is to meet the DOE need by developing new experimental approaches to describe adsorption and transport of contaminants in heterogeneous, variably saturated media (i.e., the vadose zone). The research specifically addresses the behavior of strontium, a high priority DOE contaminant. However, the key benefit of this research is improved conceptual models of how all contaminants migrate through heterogeneous, variably-saturated, porous media. Research activities are driven by the hypothesis that the reactivity of variably saturated porous media is dependent on the moisture content of the medium and can be represented by a relatively simple function applicable over a range of scales, contaminants, and media. A key and novel aspect of our research is the use of the 2-meter radius geocentrifuge capabilities at the Idaho National Laboratory (INL) to conduct unsaturated reactive transport experiments (Figure 1). The experimental approach using the geocentrifuge provides data in a much shorter time period than conventional methods allowing us to complete more experiments and explore a wider range of moisture contents. The vadose zone research being done in this project will demonstrate the utility of environmental geocentrifuge experimental approaches and their applicability to DOE’s vadose research needs.
Date: June 15, 2003
Creator: Palmer, Carl D.; Mattson, Earl D. & Smith, Robert W.
Partner: UNT Libraries Government Documents Department

Coupled Biogeochemical Processes Governing the Stability of Bacteriogenic Uraninite and Release of U(VI) in Heterogeneous Media: Molecular to Meter Scales

Description: In-situ reductive biotransformation of subsurface U(VI) to U(IV) (as ?UO2?) has been proposed as a bioremediation method to immobilize uranium at contaminated DOE sites. The chemical stability of bacteriogenic ?UO2? is the seminal issue governing its success as an in-situ waste form in the subsurface. The structure and properties of chemically synthesized UO2+x have been investigated in great detail. It has been found to exhibit complex structural disorder, with nonstoichiometry being common, hence the designation ?UO2+x?, where 0 < x < 0.25. Little is known about the structures and properties of the important bacteriogenic analogs, which are believed to occur as nanoparticles in the environment. Chemically synthesized UO2+x exhibits an open fluorite structure and is known to accommodate significant doping of divalent cations. The extent to which bacteriogenic UO2+x incorporates common ground water cations (e.g., Ca2+) has not been investigated, and little is known about nonstoichiometry and structure defects in the bacteriogenic material. Particle size, nonstoichiometry, and doping may significantly alter the reactivity, and hence stability, of bacteriogenic UO2+x in the subsurface. The presence of associated sulfide minerals, and solid phase oxidants such as bacteriogenic Mn oxides may also affect the longevity of bacteriogenic UO2 in the subsurface.
Date: November 15, 2006
Creator: Bargar, John R.
Partner: UNT Libraries Government Documents Department

Dual Permeability Modeling of Flow in a Fractured Geothermal Reservoir

Description: A three dimensional fracture system synthesis and flow simulation has been developed to correlate drawdown characteristics measured in a geothermal well and to provide the basis for an analysis of tracer tests. A new dual permeability approach was developed which incorporates simulations at two levels to better represent a discrete fracture system within computer limitations. The first incorporates a discrete simulation of the largest fractures in the system plus distributed or representative element simulation of the smaller fractures. the second determines the representative element properties by discrete simulation of the smaller fractures. The fracture system was synthesized from acoustic televiewer data on the orientation and separation of three distinct fracture sets, together with additional data from the literature. Lognormal and exponential distributions of fracture spacing and radius were studied with the exponential distribution providing more reasonable results. Hydraulic apertures were estimated as a function of distance from the model boundary to a constant head boundary. Mean values of 6.7, 101 and 46 {micro}m were chosen as the most representative values for the three fracture sets. Recommendations are given for the additional fracture characterization needed to reduce the uncertainties in the model.
Date: January 21, 1986
Creator: Miller, John D. & Allman, David W.
Partner: UNT Libraries Government Documents Department