A Femtosecond-Level Fiber-Optics Timing Distribution System Using Frequency-Offset Interferometry (open access)

A Femtosecond-Level Fiber-Optics Timing Distribution System Using Frequency-Offset Interferometry

An optical fiber-based frequency and timing distribution system based on the principle of heterodyne interferometry has been in development at LBNL for several years. The fiber drift corrector has evolved from an RF-based to an optical-based system, from mechanical correctors (piezo and optical trombone) to fully electronic, and the electronics from analog to fully digital, all using inexpensive off-the-shelf commodity fiber components. Short-term optical phase jitter and long-term phase drift are both in the femtosecond range over distribution paths of 2 km or more.
Date: October 17, 2009
Creator: Staples, J. W.; Byrd, J.; Doolittle, L.; Huang, G. & Wilcox, R.
Object Type: Article
System: The UNT Digital Library
Improving electronic structure methods to predict nano-optoelectronics and nano-catalyst functions. (open access)

Improving electronic structure methods to predict nano-optoelectronics and nano-catalyst functions.

This report focuses on quantum chemistry and ab initio molecular dynamics (AIMD) calculations applied to elucidate the mechanism of the multi-step, 2-electron, electrochemical reduction of the green house gas molecule carbon dioxide (CO{sub 2}) to carbon monoxide (CO) in aqueous media. When combined with H{sub 2} gas to form synthesis ('syn') gas, CO becomes a key precursor to methane, methanol, and other useful hydrocarbon products. To elucidate the mechanism of this reaction, we apply computational electrochemistry which is a fledgling, important area of basic science critical to energy storage. This report highlights several approaches, including the calculation of redox potentials, the explicit depiction of liquid water environments using AIMD, and free energy methods. While costly, these pioneering calculations reveal the key role of hydration- and protonation-stabilization of reaction intermediates, and may inform the design of CO{sub 2}-capture materials as well as its electrochemical reduction. In the course of this work, we have also dealt with the challenges of identifying and applying electronic structure methods which are sufficiently accurate to deal with transition metal ion complex-based catalyst. Such electronic structure methods are also pertinent to the accurate modeling of actinide materials and therefore to nuclear energy research. Our multi-pronged effort towards …
Date: October 1, 2009
Creator: Nielsen, Ida Marie B.; Marzari, Nicola; Shelnutt, John Allen; Kulik, Heather J.; Medforth, Craig John & Leung, Kevin
Object Type: Report
System: The UNT Digital Library
Discovery, integration, and interrogation of biotic/abiotic materials and systems. (open access)

Discovery, integration, and interrogation of biotic/abiotic materials and systems.

Immobilization of individual cells and collections of cells in well-defined, reproducible, nano-to-microscale structures that allow structural and functional manipulation and interrogation is important for developing new classes of biotic/abiotic materials, for establishing the relationship between genotype and phenotype, and for elucidating responses to disease, injury/stress, or therapy - primary goals of biomedical research. Although there has been considerable recent progress in investigating the response of cells to chemical or topological patterns defined lithographically on 2D surfaces, it is time to advance from two-dimensional adhesion on dishes/fluidic devices to three-dimensional architectures that better represent the nanoporous, 3-D extracellular matrix (ECM). 3D immobilization in nanostructured hosts enables cells to be surrounded by other cells, maintains fluidic connectivity/accessibility, and allows development of 3-D molecular or chemical gradients that provide an instructive background to guide cellular behavior. Although 3-D cell immobilization in polymers, hydrogels, and inorganic gels has been practiced for decades, these approaches do not provide for bio/nano interfaces with 3D spatial control of topology and composition important to both the maintenance of natural cellular behavior patterns and the development of new non-native behaviors and functions. This LDRD project exploited our discovery of the ability of living cells to organize extended nanostructures and …
Date: October 1, 2009
Creator: Dunphy, Darren Robert (University of New Mexico, Albuquerque, NM); Brinker, C. Jeffrey; Ashley, Carlee E. (University of New Mexico, Albuquerque, NM); Baca, Helen Kennicott (University of New Mexico, Albuquerque, NM); Lopez, DeAnna M. (University of New Mexico, Albuquerque, NM) & Carnes, Eric C. (University of New Mexico, Albuquerque, NM)
Object Type: Report
System: The UNT Digital Library
Recent Test Results of the High Field Nb3Sn Dipole Magnet HD2 (open access)

Recent Test Results of the High Field Nb3Sn Dipole Magnet HD2

The 1 m long Nb{sub 3}Sn dipole magnet HD2, fabricated and tested at Lawrence Berkeley National Laboratory, represents a step towards the development of block-type accelerator quality magnets operating in the range of 13-15 T. The magnet design features two coil modules composed of two layers wound around a titanium-alloy pole. The layer 1 pole includes a round cutout to provide room for a bore tube with a clear aperture of 36 mm. After a first series of tests where HD2 reached a maximum bore field of 13.8 T, corresponding to an estimated peak field on the conductor of 14.5 T, the magnet was disassembled and reloaded without the bore tube and with a clear aperture increased to 43 mm. We describe in this paper the magnet training observed in two consecutive tests after the removal of the bore tube, with a comparison of the quench performance with respect to the previous tests. An analysis of the voltage signals recorded before and after training quenches is then presented and discussed, and the results of coil visual inspections reported.
Date: October 19, 2009
Creator: Ferracin, P.; Bingham, B.; Caspi, S.; Cheng, D. W.; Dietderich, D. R.; Felice, H. et al.
Object Type: Article
System: The UNT Digital Library
Jefferson Lab IEC 61508/61511 Safety PLC Based Safety System (open access)

Jefferson Lab IEC 61508/61511 Safety PLC Based Safety System

This paper describes the design of the new 12 GeV Upgrade Personnel Safety System (PSS) at the Thomas Jefferson National Accelerator Facility (TJNAF). The new PSS design is based on the implementation of systems designed to meet international standards IEC61508 and IEC 61511 for programmable safety systems. In order to meet the IEC standards, TJNAF engineers evaluated several SIL 3 Safety PLCs before deciding on an optimal architecture. In addition to hardware considerations, software quality standards and practices must also be considered. Finally, we will discuss R&D that may lead to both high safety reliability and high machine availability that may be applicable to future accelerators such as the ILC. Key words: PLC, Safety, TJNAF, SIL, PSS, PPS, Software, ILC Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
Date: October 1, 2009
Creator: Kelly Mahoney, Henry Robertson
Object Type: Article
System: The UNT Digital Library
Integrated process modeling for the laser inertial fusion Energy (LIFE) generation system (open access)

Integrated process modeling for the laser inertial fusion Energy (LIFE) generation system

A concept for a new fusion-fission hybrid technology is being developed at Lawrence Livermore National Laboratory. The primary application of this technology is base-load electrical power generation. However, variants of the baseline technology can be used to 'burn' spent nuclear fuel from light water reactors or to perform selective transmutation of problematic fission products. The use of a fusion driver allows very high burn-up of the fission fuel, limited only by the radiation resistance of the fuel form and system structures. As a part of this process, integrated process models have been developed to aid in concept definition. Several models have been developed. A cost scaling model allows quick assessment of design changes or technology improvements on cost of electricity. System design models are being used to better understand system interactions and to do design trade-off and optimization studies. Here we describe the different systems models and present systems analysis results. Different market entry strategies are discussed along with potential benefits to US energy security and nuclear waste disposal. Advanced technology options are evaluated and potential benefits from additional R&D targeted at the different options is quantified.
Date: October 22, 2009
Creator: Meier, W. R.; Anklam, T. M.; Erlandson, A. C.; Miles, R. R.; Simon, A. J.; Sawicki, R. et al.
Object Type: Article
System: The UNT Digital Library
AAAR 28th Annual Conference Symposia Focusing on Topics of Interest to the U.S. DOE Atmospheric Science Program - October 26-30, 2009 (open access)

AAAR 28th Annual Conference Symposia Focusing on Topics of Interest to the U.S. DOE Atmospheric Science Program - October 26-30, 2009

This report addresses the secondary aerosol is an important component of atmospheric fine particles that generally consists of organics, sulfates, and nitrates.
Date: October 26, 2009
Creator: Ziemann, Paul
Object Type: Article
System: The UNT Digital Library
Scaling to 150K cores: recent algorithm and performance engineering developments enabling XGC1 to run at scale (open access)

Scaling to 150K cores: recent algorithm and performance engineering developments enabling XGC1 to run at scale

Particle-in-cell (PIC) methods have proven to be eft#11;ective in discretizing the Vlasov-Maxwell system of equations describing the core of toroidal burning plasmas for many decades. Recent physical understanding of the importance of edge physics for stability and transport in tokamaks has lead to development of the fi#12;rst fully toroidal edge PIC code - XGC1. The edge region poses special problems in meshing for PIC methods due to the lack of closed flux surfaces, which makes fi#12;eld-line following meshes and coordinate systems problematic. We present a solution to this problem with a semi-#12;field line following mesh method in a cylindrical coordinate system. Additionally, modern supercomputers require highly concurrent algorithms and implementations, with all levels of the memory hierarchy being effe#14;ciently utilized to realize optimal code performance. This paper presents a mesh and particle partitioning method, suitable to our meshing strategy, for use on highly concurrent cache-based computing platforms.
Date: October 1, 2009
Creator: Adams, Mark F.; Ku, Seung-Hoe; Worley, Patrick; D'Azevedo, Ed; Cummings, Julian C. & Chang, C. S.
Object Type: Article
System: The UNT Digital Library
Impacts of the 2009 IECC for Residential Buildings at State Level (open access)

Impacts of the 2009 IECC for Residential Buildings at State Level

This report examines the requirements of the 2009 International Energy Conservation Code® (IECC) on residential buildings on a state-by-state basis with a separate, stand-alone chapter for each state. A summary of the requirements of the code is given for each state. The 2009 IECC is then compared to the current state code for most states or typical current construction practice for the states that do not have a residential energy efficiency code. This is the final version of a draft report by the same name that was previously cleared for release (ERICA # PNNL-18545).
Date: October 1, 2009
Creator: Lucas, Robert G. & Cole, Pamala C.
Object Type: Report
System: The UNT Digital Library
Hot Electron Generation and Transport Using K(alpha) Emission (open access)

Hot Electron Generation and Transport Using K(alpha) Emission

We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40{micro}m diameter wire emulating a 40{micro}m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of prepulse level inside the cone by a factor of 50 reduces coupling by a factor of 3.
Date: October 15, 2009
Creator: Akli, K. U.; Stephens, R. B.; Key, M. H.; Bartal, T.; Beg, F. N.; Chawla, S. et al.
Object Type: Article
System: The UNT Digital Library
Gene Expression in the Third Dimension: The ECM-nucleus Connection (open access)

Gene Expression in the Third Dimension: The ECM-nucleus Connection

Decades ago, we and others proposed that the dynamic interplay between a cell and its surrounding environment dictates cell phenotype and tissue structure. Whereas much has been discovered about the effects of extracellular matrix molecules on cell growth and tissue specific gene expression, the nuclear mechanisms through which these molecules promote these physiological events remain unknown. Using mammary epithelial cells as a model, the purpose of this review is to discuss how the extracellular matrix influences nuclear structure and function in a three-dimensional context to promote epithelial morphogenesis and function in the mammary gland.
Date: October 1, 2009
Creator: Spencer, Virginia A; Xu, Ren & Bissell, Mina
Object Type: Article
System: The UNT Digital Library
Parallel digital forensics infrastructure. (open access)

Parallel digital forensics infrastructure.

This report documents the architecture and implementation of a Parallel Digital Forensics infrastructure. This infrastructure is necessary for supporting the design, implementation, and testing of new classes of parallel digital forensics tools. Digital Forensics has become extremely difficult with data sets of one terabyte and larger. The only way to overcome the processing time of these large sets is to identify and develop new parallel algorithms for performing the analysis. To support algorithm research, a flexible base infrastructure is required. A candidate architecture for this base infrastructure was designed, instantiated, and tested by this project, in collaboration with New Mexico Tech. Previous infrastructures were not designed and built specifically for the development and testing of parallel algorithms. With the size of forensics data sets only expected to increase significantly, this type of infrastructure support is necessary for continued research in parallel digital forensics. This report documents the implementation of the parallel digital forensics (PDF) infrastructure architecture and implementation.
Date: October 1, 2009
Creator: Liebrock, Lorie M. (New Mexico Tech, Socorro, NM) & Duggan, David Patrick
Object Type: Report
System: The UNT Digital Library
New Beam Loss Monitor for 12 GeV Upgrade (open access)

New Beam Loss Monitor for 12 GeV Upgrade

This paper describes a new VME based machine protection Beam Loss Monitor (BLM) signal processing board designed at Jefferson Lab to replace the current CAMAC based BLM board. The new eight-channel BLM signal processor has linear, logarithmic, and integrating amplifiers that simultaneously provide the optimal signal processing for each application. Amplified signals are digitized and then further processed through a Field Programmable Gate Array (FPGA). Combining both the diagnostic and machine protection functions in each channel allows the operator to tune-up and monitor beam operations while the machine protection is integrating the same signal. Other features include extensive built-in-self-test, fast shutdown interface (FSD), and 16-Mbit buffers for beam loss transient play-back. The new VME BLM board features high sensitivity, high resolution, and low cost per channel.
Date: October 1, 2009
Creator: Jianxun Yan, Kelly Mahoney
Object Type: Article
System: The UNT Digital Library
Alternative Waste Forms for Electro-Chemical Salt Waste (open access)

Alternative Waste Forms for Electro-Chemical Salt Waste

This study was undertaken to examine alternate crystalline (ceramic/mineral) and glass waste forms for immobilizing spent salt from the Advanced Fuel Cycle Initiative (AFCI) electrochemical separations process. The AFCI is a program sponsored by U.S. Department of Energy (DOE) to develop and demonstrate a process for recycling spent nuclear fuel (SNF). The electrochemical process is a molten salt process for the reprocessing of spent nuclear fuel in an electrorefiner and generates spent salt that is contaminated with alkali, alkaline earths, and lanthanide fission products (FP) that must either be cleaned of fission products or eventually replaced with new salt to maintain separations efficiency. Currently, these spent salts are mixed with zeolite to form sodalite in a glass-bonded waste form. The focus of this study was to investigate alternate waste forms to immobilize spent salt. On a mole basis, the spent salt is dominated by alkali and Cl with minor amounts of alkaline earth and lanthanides. In the study reported here, we made an effort to explore glass systems that are more compatible with Cl and have not been previously considered for use as waste forms. In addition, alternate methods were explored with the hope of finding a way to produce …
Date: October 28, 2009
Creator: Crum, Jarrod V.; Sundaram, S. K.; Riley, Brian J.; Matyas, Josef; Arreguin, Shelly A. & Vienna, John D.
Object Type: Report
System: The UNT Digital Library
Individual Dose Calculations with Use of the Revised Techa River Dosimetry System TRDS-2009D (open access)

Individual Dose Calculations with Use of the Revised Techa River Dosimetry System TRDS-2009D

An updated deterministic version of the Techa River Dosimetry System (TRDS-2009D) has been developed to estimate individual doses from external exposure and intake of radionuclides for residents living on the Techa River contaminated as a result of radioactive releases from the Mayak plutonium facility in 1949–1956. The TRDS-2009D is designed as a flexible system that uses, depending on the input data for an individual, various elements of system databases to provide the dosimetric variables requested by the user. Several phases are included in the computation schedule. The first phase includes calculations with use of a common protocol for all cohort members based on village-average-intake functions and external dose rates; individual data on age, gender and history of residence are included in the first phase. This phase results in dose estimates similar to those obtained with system TRDS-2000 used previously to derive risks of health effects in the Techa River Cohort. The second phase includes refinement of individual internal doses for those persons who have had body-burden measurements or exposure parameters specific to the household where he/she lived on the Techa River. The third phase includes summation of individual doses from environmental exposure and from radiological examinations. The results of TRDS-2009D …
Date: October 23, 2009
Creator: Degteva, M. O.; Shagina, N. B.; Tolstykh, E. I.; Vorobiova, M. I.; Anspaugh, L. R. & Napier, Bruce A.
Object Type: Report
System: The UNT Digital Library
Summary of the 19th International Conference on Arabidopsis Research (July 23-27, 2008 in Montreal, Canada) (open access)

Summary of the 19th International Conference on Arabidopsis Research (July 23-27, 2008 in Montreal, Canada)

The 19th International Conference on Arabidopsis Research was a successful meeting attended by 815 scientists from around the world including 322 from the United States, 146 attendees from Canada, 179 from Europe, 134 from Asia, and 34 from a combination of Australia, South America, Africa and the Middle East. The scientific program was of excellent quality featuring 64 talks, including 41 from invited speakers. The Keynote Lecture, delivered by Chris Somerville (Energy Biosciences Institute/UC Berkeley) was particularly relevant to US agriculture and energy research and was titled The Development of Cellulosic Biofuels. There were also 6 community-organized workshops featuring 30 additional talks on topics including Frontiers in Plant Systems Biology, Sources and strategies for Gene Structure, Gene Function, and Metabolic Pathway annotation at TAIR and AraCyc, Advanced Bioinformatic Resources for Arabidopsis, Laser Microtechniques and Applications with Arabidopsis, Plant Proteomics- Tools, Approaches, Standards and Breakthroughs in Studying the Proteome, and Phytohormone Biosynthesis and Signal Transduction. Conference organizers arranged a special seminar by Jim Collins (head of the Directorate of Biosciences at NSF) to provide a community discussion forum regarding the future of Arabidopsis research. Approximately 575 posters were presented in topic areas including, among others, Development, Signal Transduction, Cell Walls, Non-Arabidopsis …
Date: October 1, 2009
Creator: Schroeder, Julian I.
Object Type: Report
System: The UNT Digital Library
Systems engineering management plans. (open access)

Systems engineering management plans.

The Systems Engineering Management Plan (SEMP) is a comprehensive and effective tool used to assist in the management of systems engineering efforts. It is intended to guide the work of all those involved in the project. The SEMP is comprised of three main sections: technical project planning and control, systems engineering process, and engineering specialty integration. The contents of each section must be tailored to the specific effort. A model outline and example SEMP are provided. The target audience is those who are familiar with the systems engineering approach and who have an interest in employing the SEMP as a tool for systems management. The goal of this document is to provide the reader with an appreciation for the use and importance of the SEMP, as well as provide a framework that can be used to create the management plan.
Date: October 1, 2009
Creator: Rodriguez, Tamara S.
Object Type: Report
System: The UNT Digital Library
Nambe Pueblo Water Budget and Forecasting model. (open access)

Nambe Pueblo Water Budget and Forecasting model.

This report documents The Nambe Pueblo Water Budget and Water Forecasting model. The model has been constructed using Powersim Studio (PS), a software package designed to investigate complex systems where flows and accumulations are central to the system. Here PS has been used as a platform for modeling various aspects of Nambe Pueblo's current and future water use. The model contains three major components, the Water Forecast Component, Irrigation Scheduling Component, and the Reservoir Model Component. In each of the components, the user can change variables to investigate the impacts of water management scenarios on future water use. The Water Forecast Component includes forecasting for industrial, commercial, and livestock use. Domestic demand is also forecasted based on user specified current population, population growth rates, and per capita water consumption. Irrigation efficiencies are quantified in the Irrigated Agriculture component using critical information concerning diversion rates, acreages, ditch dimensions and seepage rates. Results from this section are used in the Water Demand Forecast, Irrigation Scheduling, and the Reservoir Model components. The Reservoir Component contains two sections, (1) Storage and Inflow Accumulations by Categories and (2) Release, Diversion and Shortages. Results from both sections are derived from the calibrated Nambe Reservoir model where …
Date: October 1, 2009
Creator: Brainard, James Robert
Object Type: Report
System: The UNT Digital Library
Challenges and opportunities in high-precision Be-10 measurements at CAMS (open access)

Challenges and opportunities in high-precision Be-10 measurements at CAMS

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Date: October 12, 2009
Creator: Rood, D. H.; Hall, S.; Guilderson, T. P.; Finkel, R. C. & Brown, T. A.
Object Type: Article
System: The UNT Digital Library
Fast Ignition Transport Simulations for NIF (open access)

Fast Ignition Transport Simulations for NIF

This paper shows work at Lawrence Livermore National Lab (LLNL) devoted to modeling the propagation of, and heating by, a relativistic electron beam in a idealized dense fuel assembly for fast ignition. The implicit particle-in-cell (PIC) code LSP is used. Experiments planned on the National Ignition Facility (NIF) in the next few years using the Advanced Radiography Capability (ARC) short-pulse laser motivate this work. We demonstrate significant improvement in the heating of dense fuel due to magnetic forces, increased beam collimation, and insertion of a finite-radius carbon region between the beam excitation and fuel regions.
Date: October 5, 2009
Creator: Strozzi, D J; Grote, D P; Tabak, M; Cohen, B I; Town, R P & Kemp, A J
Object Type: Article
System: The UNT Digital Library
Hanford and the Tri-Cities Economy: Historical Trends 1970-2008 (open access)

Hanford and the Tri-Cities Economy: Historical Trends 1970-2008

This white paper examines the effect that the Hanford Site has had on the Tri-Cities economy from 1970-2008. Total area employment levels, population, and the real estate market are compared to DOE contractor employment and funding levels, which tended to follow each other until the mid-1990s. Since 1994, area employment, total incomes, population and the real estate market have increased significantly despite very little changes in Hanford employment levels. The data indicate that in recent history, the Tri-Cities economy has become increasingly independent of Hanford.
Date: October 1, 2009
Creator: Fowler, Richard A. & Scott, Michael J.
Object Type: Report
System: The UNT Digital Library
REAL WASTE TESTING OF SPHERICAL RESORCINOL-FORMALDEHYDE ION EXCHANGE RESIN (open access)

REAL WASTE TESTING OF SPHERICAL RESORCINOL-FORMALDEHYDE ION EXCHANGE RESIN

This report presents data on batch contact and column testing tasks for spherical resorcinol-formaldehyde (sRF) resin. The testing used a non-radioactive simulant of SRS Tank 2F dissolved salt, as well as an actual radioactive waste sample of similar composition, which are both notably high in sodium (6 M). The resin was Microbeads batch 5E-370/641 which had been made on the hundred gallon scale. Equilibrium batch contact work focused on cesium at a temperature of 25 C due to the lack of such data to better benchmark existing isotherm models. Two campaigns were performed with small-scale ion exchange columns, first with Tank 2F simulant, then with actual dissolved salt in the Shielded Cells. An extrapolation of the batch contact results with radioactive waste over-predicted the cesium loaded onto the IX sRF resin bed by approximately 11%. This difference is not unexpected considering uncertainties from measurement and extrapolation and because the ion exchange that occurs when waste flows through a resin bed probably cannot reach the same level of equilibrium as when waste and resin are joined in a long term batch contact. Resin was also characterized to better understand basic chemistry issues such as holdup of trace transition metals present in …
Date: October 30, 2009
Creator: Nash, C. & Duignan, M.
Object Type: Report
System: The UNT Digital Library
Review and Analysis of Development of "Safety by Design" Requirements (open access)

Review and Analysis of Development of "Safety by Design" Requirements

This report, the deliverable for Task 4 of the NA-243 Safeguards by Design Work Plan for Fiscal Year 2009, develops the lessons to be learned for the institutionalization of Safeguards By Design (SBD) from the Department of Energy (DOE) experience developing and implementing DOE-STD-1189, Integration of Safety into the Design Process. This experience was selected for study because of the similarity of the challenges of integrating safety and safeguards into the design process. Development of DOE-STD-1189 began in January 2006 and the standard was issued for implementation in March 2008. The process was much more time consuming than originally anticipated and might not have come to fruition had senior DOE management been less committed to its success. Potentially valuable lessons can be learned from both the content and presentation of the integration approach in DOE-STD-1189 and from the DOE experience in developing and implementing DOE-STD-1189. These lessons are important because the instutionalization of SBD does not yet appear to have the level of senior management commitment afforded development and implementation of DOE-STD-1189.
Date: October 20, 2009
Creator: Vance, Scott A. & Hockert, John
Object Type: Report
System: The UNT Digital Library
Fracture Propagation and Permeability Change under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems (open access)

Fracture Propagation and Permeability Change under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems

Geothermal energy is recovered by circulating water through heat exchange areas within a hot rock mass. Geothermal reservoir rock masses generally consist of igneous and metamorphic rocks that have low matrix permeability. Therefore, cracks and fractures play a significant role in extraction of geothermal energy by providing the major pathways for fluid flow and heat exchange. Therefore, knowledge of the conditions leading to formation of fractures and fracture networks is of paramount importance. Furthermore, in the absence of natural fractures or adequate connectivity, artificial fractures are created in the reservoir using hydraulic fracturing. Multiple fractures are preferred because of the large size necessary when using only a single fracture. Although the basic idea is rather simple, hydraulic fracturing is a complex process involving interactions of high pressure fluid injections with a stressed hot rock mass, mechanical interaction of induced fractures with existing natural fractures, and the spatial and temporal variations of in-situ stress. As a result, it is necessary to develop tools that can be used to study these interactions as an integral part of a comprehensive approach to geothermal reservoir development, particularly enhanced geothermal systems. In response to this need we have developed advanced poro-thermo-chemo-mechanical fracture models for rock …
Date: October 2009
Creator: Ghassemi, Ahmad
Object Type: Report
System: The UNT Digital Library