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Task 1 Steam Oxidation (NETL-US)

Description: Some conclusions are: (1) Increased flow rates can lower chromia activity in alloys with Ti and Mn - (a) Reduced chromia activity reduces equilibrium CrO{sub 2}(OH){sub 2}(g) vapor pressures; (2) Model is very sensitive to small decreases in chromia activity at the HP turbine - (a) Upstream partial saturation of the gas phase with CrO{sub 2}(OH){sub 2}(g) can become nearly or fully saturated at the HP turbine, (b) Can radically change breakaway oxidation times from less than a year to never happening; and (3) Thus even small chromia activity reductions from Ti and Mn additions can make evaporation issues self-correcting.
Date: April 28, 2011
Creator: Holcomb, G. R.; Tylczak, J. & R. Hu,
Partner: UNT Libraries Government Documents Department

POTENTIAL FOR STRESS CORROSION CRACKING OF A537 CARBON STEEL NUCLEAR WASTE TANKS CONTAINING HIGHLY CAUSTIC SOLUTIONS

Description: The evaporator recycle streams of nuclear waste tanks may contain waste in a chemistry and temperature regime that exceeds the current corrosion control program, which imposes temperature limits to mitigate caustic stress corrosion cracking (CSCC). A review of the recent service history found that two of these A537 carbon steel tanks were operated in highly concentrated hydroxide solution at high temperature. Visual inspections, experimental testing, and a review of the tank service history have shown that CSCC has occurred in uncooled/un-stress relieved tanks of similar construction. Therefore, it appears that the efficacy of stress relief of welding residual stress is the primary corrosion-limiting mechanism. The objective of this experimental program is to test A537 carbon steel small scale welded U-bend specimens and large welded plates (30.48 x 30.38 x 2.54 cm) in a caustic solution with upper bound chemistry (12 M hydroxide and 1 M each of nitrate, nitrite, and aluminate) and temperature (125 C). These conditions simulate worst-case situations in these nuclear waste tanks. Both as-welded and stress-relieved specimens have been tested. No evidence of stress corrosion cracking was found in the U-bend specimens after 21 days of testing. The large plate test was completed after 12 weeks of immersion in a similar solution at 125 C except that the aluminate concentration was reduced to 0.3 M. Visual inspection of the plate revealed that stress corrosion cracking had not initiated from the machined crack tips in the weld or in the heat affected zone. NDE ultrasonic testing also confirmed subsurface cracking did not occur. Based on these results, it can be concluded that the environmental condition of these tests was unable to develop stress corrosion cracking within the test periods for the small welded U-bends and for the large plates, which were welded with an identical procedure as used ...
Date: April 26, 2010
Creator: Lam, P.; Stripling, C.; Fisher, D. & Elder, J.
Partner: UNT Libraries Government Documents Department

Numerical errors in the presence of steep topography: analysis and alternatives

Description: It is well known in computational fluid dynamics that grid quality affects the accuracy of numerical solutions. When assessing grid quality, properties such as aspect ratio, orthogonality of coordinate surfaces, and cell volume are considered. Mesoscale atmospheric models generally use terrain-following coordinates with large aspect ratios near the surface. As high resolution numerical simulations are increasingly used to study topographically forced flows, a high degree of non-orthogonality is introduced, especially in the vicinity of steep terrain slopes. Numerical errors associated with the use of terrainfollowing coordinates can adversely effect the accuracy of the solution in steep terrain. Inaccuracies from the coordinate transformation are present in each spatially discretized term of the Navier-Stokes equations, as well as in the conservation equations for scalars. In particular, errors in the computation of horizontal pressure gradients, diffusion, and horizontal advection terms have been noted in the presence of sloping coordinate surfaces and steep topography. In this work we study the effects of these spatial discretization errors on the flow solution for three canonical cases: scalar advection over a mountain, an atmosphere at rest over a hill, and forced advection over a hill. This study is completed using the Weather Research and Forecasting (WRF) model. Simulations with terrain-following coordinates are compared to those using a flat coordinate, where terrain is represented with the immersed boundary method. The immersed boundary method is used as a tool which allows us to eliminate the terrain-following coordinate transformation, and quantify numerical errors through a direct comparison of the two solutions. Additionally, the effects of related issues such as the steepness of terrain slope and grid aspect ratio are studied in an effort to gain an understanding of numerical domains where terrain-following coordinates can successfully be used and those domains where the solution would benefit from the use of the ...
Date: April 15, 2010
Creator: Lundquist, K A; Chow, F K & Lundquist, J K
Partner: UNT Libraries Government Documents Department

DEVELOPMENT OF ASME SECTION X CODE RULES FOR HIGH PRESSURE COMPOSITE HYDROGEN PRESSURE VESSELS WITH NON-LOAD SHARING LINERS

Description: The Boiler and Pressure Vessel Project Team on Hydrogen Tanks was formed in 2004 to develop Code rules to address the various needs that had been identified for the design and construction of up to 15000 psi hydrogen storage vessel. One of these needs was the development of Code rules for high pressure composite vessels with non-load sharing liners for stationary applications. In 2009, ASME approved new Appendix 8, for Section X Code which contains the rules for these vessels. These vessels are designated as Class III vessels with design pressure ranging from 20.7 MPa (3,000 ps)i to 103.4 MPa (15,000 psi) and maximum allowable outside liner diameter of 2.54 m (100 inches). The maximum design life of these vessels is limited to 20 years. Design, fabrication, and examination requirements have been specified, included Acoustic Emission testing at time of manufacture. The Code rules include the design qualification testing of prototype vessels. Qualification includes proof, expansion, burst, cyclic fatigue, creep, flaw, permeability, torque, penetration, and environmental testing.
Date: April 13, 2010
Creator: Rawls, G.; Newhouse, N.; Rana, M.; Shelley, B. & Gorman, M.
Partner: UNT Libraries Government Documents Department

An Evaluation of Atmospheric-pressure Plasma for the Cost-Effective Deposition of Antireflection Coatings

Description: Atmospheric-pressure plasma deposition (APPD) has previously been used to deposit various functional materials including polymeric surface modification layers, transparent conducting oxides, and photo catalytic materials. For many plasma polymerized coatings, reaction occurs via free radical mechanism where the high energy electrons from the plasma activate the olefinic carbon-carbon double bonds - a typical functional group in such precursors. The precursors for such systems are typically inexpensive and readily available and have been used in vacuum PECVD previously. The objectives are to investigate: (1) the effect of plasma power, gas composition and substrate temperature on the Si-based film properties using triethylsilane(TES) as the precursor; and (2) the chemical, mechanical, and optical properties of several experimental matrices based on Design of Experiment (DOE) principals. A simple APPD route has been utilized to deposit Si based films from an inexpensive precursor - Triethylsilane (TES). Preliminary results indicates formation of Si-C & Si-O and Si-O, Si-C & Si-N bonds with oxygen and nitrogen plasmas respectively. N{sub 2}-O{sub 2} plasma showed mixed trend; however oxygen remains a significant portion of all films, despite attempts to minimize exposure to atmosphere. SiN, SiC, and SiO ratios can be modified by the reaction conditions resulting in differing film properties. SE studies revealed that films with SiN bond possess refractive index higher than coatings with Si-O/Si-C bonds. Variable angle reflectance studies showed that SiOCN coatings offer AR properties; however thickness and refractive index optimization of these coatings remains necessary for application as potential AR coatings.
Date: April 1, 2010
Creator: Sailer, Rob; Srinivasan, Guruvenket; Johnson, Kyle W. & Schulz, Douglas L.
Partner: UNT Libraries Government Documents Department

LITERATURE SURVEY OF GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS

Description: Literature survey has been performed for a compendium of mechanical properties of carbon and low alloy steels following hydrogen exposure. The property sets include yield strength, ultimate tensile strength, uniform elongation, reduction of area, threshold stress intensity factor, fracture toughness, and fatigue crack growth. These properties are drawn from literature sources under a variety of test methods and conditions. However, the collection of literature data is by no means complete, but the diversity of data and dependency of results in test method is sufficient to warrant a design and implementation of a thorough test program. The program would be needed to enable a defensible demonstration of structural integrity of a pressurized hydrogen system. It is essential that the environmental variables be well-defined (e.g., the applicable hydrogen gas pressure range and the test strain rate) and the specimen preparation be realistically consistent (such as the techniques to charge hydrogen and to maintain the hydrogen concentration in the specimens).
Date: April 27, 2009
Creator: Lam, P; Andrew Duncan, A; Robert Sindelar, R & Thad Adams, T
Partner: UNT Libraries Government Documents Department

THERMAL EVALUATION OF DRUM TYPE RADIOACTIVE MATERIAL PACKAGING ARRAYS IN STORAGE

Description: Drum type packages are routinely used to transport radioactive material (RAM) in the U.S. Department of Energy (DOE) complex. These packages are designed to meet the federal regulations described in 10 CFR 71.[1] In recent years, there has been a greater need to use these packagings to store the excess fissile material, especially plutonium for long term storage. While the design requirements for safe transportation of these packagings are well defined, the requirements for safe long term storage are not well established. Since the RAM contents in the packagings produce decay heat, it is important that they are stored carefully to prevent overheating of the containment vessel (CV) seals to prevent any leakage and the impact limiter to maintain the package structural integrity. This paper analyzes different storage arrays for a typical 9977 packaging for thermal considerations and makes recommendations for their safe storage under normal operating conditions.
Date: April 27, 2009
Creator: Gupta, N
Partner: UNT Libraries Government Documents Department

Restructuring of hex-Pt(100) under CO gas environments: formation of 2-D nanoclusters

Description: The atomic-scale restructuring of hex-Pt(100) induced by carbon monoxide with a wide pressure range was studied with a newly designed chamber-in-chamber high-pressure STM and theoretical calculations. Both experimental and DFT calculation results show that CO molecules are bound to Pt nanoclusters through a tilted on-top configuration with a separation of {approx}3.7-4.1 {angstrom}. The phenomenon of restructuring of metal catalyst surfaces induced by adsorption, and in particular the formation of small metallic clusters suggests the importance of studying structures of catalyst surfaces under high pressure conditions for understanding catalytic mechanisms.
Date: April 24, 2009
Creator: Tao, Feng; Dag, Sefa; Wang, Lin-Wang; Liu, Zhi; Butcher, Derek; Salmeron, Miquel et al.
Partner: UNT Libraries Government Documents Department

Review of Recent Aging-Related Degradation Occurrences of Structures and Passive Components in U.S. Nuclear Power Plants

Description: The Korea Atomic Energy Research Institute (KAERI) and Brookhaven National Laboratory (BNL) are collaborating to develop seismic capability evaluation technology for degraded structures and passive components (SPCs) under a multi-year research agreement. To better understand the status and characteristics of degradation of SPCs in nuclear power plants (NPPs), the first step in this multi-year research effort was to identify and evaluate degradation occurrences of SPCs in U.S. NPPs. This was performed by reviewing recent publicly available information sources to identify and evaluate the characteristics of degradation occurrences and then comparing the information to the observations in the past. Ten categories of SPCs that are applicable to Korean NPPs were identified, comprising of anchorage, concrete, containment, exchanger, filter, piping system, reactor pressure vessel, structural steel, tank, and vessel. Software tools were developed to expedite the review process. Results from this review effort were compared to previous data in the literature to characterize the overall degradation trends.
Date: April 2, 2009
Creator: Nie,J.; Braverman, J.; Hofmayer, C.; Choun, Y.-S.; Kim, M.K. & Choi, I.-K.
Partner: UNT Libraries Government Documents Department

Advanced Computational Thermal Studies and their Assessment for Supercritical-Pressure Reactors (SCRs)

Description: The goal of this laboratory / university collaboration of coupled computational and experimental studies is the improvement of predictive methods for supercritical-pressure reactors. The general objective is to develop supporting knowledge needed of advanced computational techniques for the technology development of the concepts and their safety systems.
Date: April 1, 2009
Creator: McEligot, D. M.; Yoo, J. Y.; Lee, J. S.; Ro, S. T.; Lurien, E.; Park, S. O. et al.
Partner: UNT Libraries Government Documents Department

Airflow Simulations around OA Intake Louver with Electronic Velocity Sensors

Description: It is important to control outdoor airflow rates into HVAC systems in terms of energy conservation and healthy indoor environment. Technologies are being developed to measure outdoor air (OA) flow rates through OA intake louvers on a real time basis. The purpose of this paper is to investigate the airflow characteristics through an OA intake louver numerically in order to provide suggestions for sensor installations. Airflow patterns are simulated with and without electronic air velocity sensors within cylindrical probes installed between louver blades or at the downstream face of the louver. Numerical results show quite good agreements with experimental data, and provide insights regarding measurement system design. The simulations indicate that velocity profiles are more spatially uniform at the louver outlet relative to between louver blades, that pressure drops imposed by the sensor bars are smaller with sensor bars at the louver outlet, and that placement of the sensor bars between louver blades substantially increases air velocities inside the louver. These findings suggest there is an advantage to placing the sensor bars at the louver outlet face.
Date: April 1, 2009
Creator: Han, Hwataik; Sullivan, Douglas P. & Fisk, William J.
Partner: UNT Libraries Government Documents Department

PBXN-9 Ignition Kinetics and Deflagration Rates

Description: The ignition kinetics and deflagration rates of PBXN-9 were measured using specially designed instruments at LLNL and compared with previous work on similar HMX based materials. Ignition kinetics were measured based on the One Dimensional Time-to-Explosion combined with ALE3D modeling. Results of these experiments indicate that PBXN-9 behaves much like other HMX based materials (i.e. LX-04, LX-07, LX-10 and PBX-9501) and the dominant factor in these experiments is the type of explosive, not the type of binder/plasticizer. In contrast, the deflagration behavior of PBXN-9 is quite different from similar high weight percent HMX based materials (i.e LX-10, LX-07 and PBX-9501). PBXN-9 burns in a laminar manner over the full pressure range studied (0-310 MPa) unlike LX-10, LX-07, and PBX-9501. The difference in deflagration behavior is attributed to the nature of the binder/plasticizer alone or in conjunction with the volume of binder present in PBXN-9.
Date: April 24, 2008
Creator: Glascoe, E; Maienschein, J; Burnham, A; Koerner, J; Hsu, P & Wemhoff, A
Partner: UNT Libraries Government Documents Department

Geomechanical Simulations of Caprock Integrity Using the Livermore Distinict Element Method

Description: Large-scale carbon capture and sequestration (CCS) projects involving annual injections of millions of tons of CO2 are a key infrastructural element needed to substantially reduce greenhouse gas emissions. The large rate and volume of injection will induce pressure and stress gradients within the formation that could activate existing fractures and faults, or drive new fractures through the caprock. We will present results of an ongoing investigation to identify conditions that will activate existing fractures/faults or make new fractures within the caprock using the Livermore Distinct Element Code (LDEC). LDEC is a multiphysics code, developed at LLNL, capable of simulating dynamic fracture of rock masses under a range of conditions. As part of a recent project, LDEC has been extended to consider fault activation and dynamic fracture of rock masses due to pressurization of the pore-space. We will present several demonstrations of LDEC functionality and an application of LDEC to a CO2 injection scenario. We present results from our investigations of Teapot Dome using LDEC to study the potential for fault activation during injection. Using this approach, we built finite element models of the rock masses surrounding bounding faults and explicitly simulated the compression and shear on the fault interface. A CO2 injection source was introduced and the area of fault activation was predicted as a function of injection rate. This work presents an approach where the interactions of all locations on the fault are considered in response to specific injection scenarios. For example, with LDEC, as regions of the fault fail, the shear load is taken up elsewhere on the fault. The results of this study are consistent with previous studies of Teapot Dome and indicate significantly elevated pore pressures are required to activate the bounding faults, given the assumed in situ stress state on the faults.
Date: April 17, 2008
Creator: Morris, J; Johnson, S & Friedmann, S J
Partner: UNT Libraries Government Documents Department

PREDICTION OF CHARACTERISTIC LENGTH AND FRACTURE TOUGHNESS IN DUCTILE-BRITTLE TRANSITION

Description: Finite element method was used to analyze the three-point bend experimental data of A533B-1 pressure vessel steel obtained by Sherry, Lidbury, and Beardsmore [1] from -160 to -45 C within the ductile-brittle transition regime. As many researchers have shown, the failure stress ({sigma}{sub f}) of the material could be approximated as a constant. The characteristic length, or the critical distance (r{sub c}) from the crack tip, at which {sigma}{sub f} is reached, is shown to be temperature dependent based on the crack tip stress field calculated by the finite element method. With the J-A{sub 2} two-parameter constraint theory in fracture mechanics, the fracture toughness (J{sub C} or K{sub JC}) can be expressed as a function of the constraint level (A{sub 2}) and the critical distance r{sub c}. This relationship is used to predict the fracture toughness of A533B-1 in the ductile-brittle transition regime with a constant {sigma}{sub f} and a set of temperature-dependent r{sub c}. It can be shown that the prediction agrees well with the test data for wide range of constraint levels from shallow cracks (a/W= 0.075) to deep cracks (a/W= 0.5), where a is the crack length and W is the specimen width.
Date: April 15, 2008
Creator: Lam, P
Partner: UNT Libraries Government Documents Department

Molecular Surface Chemistry by Metal Single Crystals and Nanoparticles from Vacuum to High Pressure.

Description: Model systems for studying molecular surface chemistry have evolved from single crystal surfaces at low pressure to colloidal nanoparticles at high pressure. Low pressure surface structure studies of platinum single crystals using molecular beam surface scattering and low energy electron diffraction techniques probe the unique activity of defects, steps and kinks at the surface for dissociation reactions (H-H, C-H, C-C, O{double_bond}O bonds). High-pressure investigations of platinum single crystals using sum frequency generation vibrational spectroscopy have revealed the presence and the nature of reaction intermediates. High pressure scanning tunneling microscopy of platinum single crystal surfaces showed adsorbate mobility during a catalytic reaction. Nanoparticle systems are used to determine the role of metal-oxide interfaces, site blocking and the role of surface structures in reactive surface chemistry. The size, shape and composition of nanoparticles play important roles in determining reaction activity and selectivity.
Date: April 5, 2008
Creator: Somorjai, Gabor A. & Park, Jeong Y.
Partner: UNT Libraries Government Documents Department

Raman Shift of Stressed Diamond Anvils: Pressure Calibration and Culet Geometry Dependence

Description: The pressure dependence of the Raman shift of diamond for highly stressed anvils at the diamond-anvil sample interface has been measured for different culet shapes up to 180 GPa at ambient temperature. By using hydrogen samples, which constitute both a quasi-hydrostatic medium and a sensitive pressure sensor, some of the effects of culet and tip size have been determined. We propose that the divergent results in the literature can be partly ascribed to different anvil geometries. Experiments show increasing second order dependence of the diamond Raman shift with pressure for decreasing tip size. This is an important consideration when using the diamond anvils as a pressure sensor.
Date: April 3, 2008
Creator: Baer, B J; Chang, M E & Evans, W J
Partner: UNT Libraries Government Documents Department

Ambient-Pressure X-ray Photoelectron Spectroscopy

Description: This workshop focused on the application of ambient pressure X-ray photoelectron spectroscopy (APXPS) to environmental science and catalysis. Pioneering work on APXPS was done in the early 1970's by Hans and Kai Siegbahn et al., who demonstrated that XPS can operate at pressures of up to 1 Torr. A new type of APXPS instrument that utilizes a differentially-pumped electrostatic lens system at the ALS in 2001 increased the pressure limit to above 5 Torr, which opened the door to XPS experiments on water and aqueous solutions at temperatures above the melting point, in equilibrium with the vapor pressure of water. The impact of APXPS on fields such as environmental and atmospheric science as well as heterogeneous catalysis is already visible in numerous high impact publications. Today several other synchrotron facilities around the world have already implemented beam lines for APXPS or planning to do so in the near future. The goal of this workshop (organized by Miquel Salmeron (Molecular Foundry, LBNL), B. Simon Mun (Advanced Light Source, LBNL) and Hendrik Bluhm (Chemical Sciences Division, LBNL)) was to bring together researchers interested in the technique, review its current progress, discuss scientific opportunities and desirable technical improvements as well as consider the consequences of the increased user demand on the existing beam lines and ways to expand the availability of time.
Date: April 1, 2008
Creator: Bluhm, Hendrik; Bluhm, Hendrik; Mun, Bongjin Simon & Salmeron, Miquel
Partner: UNT Libraries Government Documents Department

HEADSPACE GAS EVALUATION OF WELDED PLUTONIUM STORAGE CONTAINERS

Description: The Can Puncture Device (CPD) serves as a containment vessel during the puncture of nested 3013 containers as part of surveillance operations in K-Area. The purpose of the CPD sampling process is to determine the original pressure and composition of gases within the inner 3013 container. The relation between the composition of the gas sample drawn from the CPD and that originally in the inner 3013 container depends on the degree of mixing that occurs over the interval of time from the puncture to drawing the sample. Gas mixing is bounded by the extremes of no mixing of gases in the inner container and that of complete mixing, in which case the entire CPD system is of uniform composition. Models relating the sample composition and pressure to the initial (pre-puncture) inner can composition and pressure for each of these extremes were developed. Predictions from both models were compared to data from characterization experiments. In the comparison, it was found that the model that assumed complete gas mixing after puncture, the Uniform Mixing Model, showed significantly better agreement with the data than the model that assumed no change in the composition of the inner container, referred to as the Non-Uniform Mixing Model. Both models were implemented as Microsoft{reg_sign} Excel spreadsheet calculations, which utilize macros, to include the effects of uncertainties and biases in the measurements of process parameters and in the models. Potential inleakage of gas from the glovebox is also addressed. The spreadsheet utilizing the Uniform Mixing Model, which was validated by data from the characterization tests, is used to evaluate the pre-puncture composition and pressure within the inner 3013 container. This spreadsheet model is called the Gas Evaluation Software Tool (GEST).
Date: April 1, 2008
Creator: Hardy, B; Stephen Harris, S; Matthew Arnold, M & Steve Hensel, S
Partner: UNT Libraries Government Documents Department

TECHNICAL BASIS AND APPLICATION OF NEW RULES ON FRACTURE CONTROL OF HIGH PRESSURE HYDROGEN VESSEL IN ASME SECTION VIII, DIVISION 3 CODE

Description: As a part of an ongoing activity to develop ASME Code rules for the hydrogen infrastructure, the ASME Boiler and Pressure Vessel Code Committee approved new fracture control rules for Section VIII, Division 3 vessels in 2006. These rules have been incorporated into new Article KD-10 in Division 3. The new rules require determining fatigue crack growth rate and fracture resistance properties of materials in high pressure hydrogen gas. Test methods have been specified to measure these fracture properties, which are required to be used in establishing the vessel fatigue life. An example has been given to demonstrate the application of these new rules.
Date: April 30, 2007
Creator: Rawls, G
Partner: UNT Libraries Government Documents Department

DEVELOPMENT AND APPLICATION OF MATERIALS PROPERTIES FOR FLAW STABILITY ANALYSIS IN EXTREME ENVIRONMENT SERVICE

Description: Discovery of aging phenomena in the materials of a structure may arise after its design and construction that impact its structural integrity. This condition can be addressed through a demonstration of integrity with the material-specific degraded conditions. Two case studies of development of fracture and crack growth property data, and their application in development of in-service inspection programs for nuclear structures in the defense complex are presented. The first case study covers the development of fracture toughness properties in the form of J-R curves for rolled plate Type 304 stainless steel with Type 308 stainless steel filler in the application to demonstrate the integrity of the reactor tanks of the heavy water production reactors at the Savannah River Site. The fracture properties for the base, weld, and heat-affected zone of the weldments irradiated at low temperatures (110-150 C) up to 6.4 dpa{sub NRT} and 275 appm helium were developed. An expert group provided consensus for application of the irradiated properties for material input to acceptance criteria for ultrasonic examination of the reactor tanks. Dr. Spencer H. Bush played a lead advisory role in this work. The second case study covers the development of fracture toughness for A285 carbon steel in high level radioactive waste tanks. The approach in this case study incorporated a statistical experimental design for material testing to address metallurgical factors important to fracture toughness. Tolerance intervals were constructed to identify the lower bound fracture toughness for material input to flaw disposition through acceptance by analysis.
Date: April 18, 2007
Creator: Sindelar, R; Ps Lam, P; Andrew Duncan, A; Bruce Wiersma, B; Karthik Subramanian, K & James Elder, J
Partner: UNT Libraries Government Documents Department

LITERATURE SURVEY OF GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS

Description: Literature survey has been performed for a compendium of mechanical properties of carbon and low alloy steels following hydrogen exposure. The property sets include yield strength, ultimate tensile strength, uniform elongation, reduction of area, threshold stress intensity factor, fracture toughness, and fatigue crack growth. These properties are drawn from literature sources under a variety of test methods and conditions. However, the collection of literature data is by no means complete, but the diversity of data and dependency of results in test method is sufficient to warrant a design and implementation of a thorough test program. The program would be needed to enable a defensible demonstration of structural integrity of a pressurized hydrogen system. It is essential that the environmental variables be well-defined (e.g., the applicable hydrogen gas pressure range and the test strain rate) and the specimen preparation be realistically consistent (such as the techniques to charge hydrogen and to maintain the hydrogen concentration in the specimens).
Date: April 18, 2007
Creator: Lam, P; Robert Sindelar, R & Thad Adams, T
Partner: UNT Libraries Government Documents Department

Simulation of Flow and Transport at the Micro (Pore) Scale

Description: An important problem in porous media involves the ability of micron and submicron-sized biological particles such as viruses or bacteria to move in groundwater systems through geologic media characterized by rock or mixed gravel, clay and sand materials. Current simulation capabilities require properly upscaled (continuum) models of colloidal filtration and adsorption to augment existing theories of fluid flow and chemical transport. Practical models typically address flow and transport behavior in aquifers over distances of 1 to 10 km where, for example, fluid momentum balance is governed by the simple Darcy's Law as a function of a pressure gradient, elevation gradient and a medium-dependent permeability parameter. In addition to fluid advection, there are multiple transport processes occurring in these systems including diffusion, dispersion and chemical interactions with solids or other aqueous chemical species. Particle transport is typically modeled in the same way as dissolved species, except that additional loss terms are incorporated to model particle filtration (physical interception), adsorption (chemical interception) and inactivation. Proper resolution of these processes at the porous medium continuum scale constitutes an important closure problem in subsurface science. We present a new simulation capability based on enabling technologies developed for microfluidics applications to model transport of colloidal-sized particles at the microscale, with relevance to the pore scale in geophysical subsurface systems. Particulate is represented by a bead-rod polymer model and is fully-coupled to a Newtonian solvent described by Navier-Stokes. Finite differences are used to discretize the interior of the domain; a Cartesian grid embedded boundary/volume-of-fluid method is used near boundaries and interfaces. This approach to complex geometry is amenable to direct simulation on grids obtained from surface extractions of tomographic image data. Short-range interactions are included in the particle model. This capability has been previously demonstrated on polymer flow in spatially-resolved packed bed (3D) and post array ...
Date: April 5, 2007
Creator: Trebotich, D & Miller, G H
Partner: UNT Libraries Government Documents Department

Carbon Dioxide Separation with Supported Ionic Liquid Membranes

Description: Supported liquid membranes are a class of materials that allow the researcher to utilize the wealth of knowledge available on liquid properties as a direct guide in the development of a capture technology. These membranes also have the advantage of liquid phase diffusivities higher than those observed in polymeric membranes which grant proportionally greater permeabilities. The primary shortcoming of the supported liquid membranes demonstrated in past research has been the lack of stability caused by volatilization of the transport liquid. Ionic liquids, which possess high carbon dioxide solubility relative to light gases such as hydrogen, are an excellent candidate for this type of membrane since they have negligible vapor pressure and are not susceptible to evaporation. A study has been conducted evaluating the use of several ionic liquids, including 1-hexyl-3-methyl-imidazolium bis(trifuoromethylsulfonyl)imide, 1-butyl-3-methyl-imidazolium nitrate, and 1-ethyl-3-methyl-imidazolium sulfate in supported ionic liquid membranes for the capture of carbon dioxide from streams containing hydrogen. In a joint project, researchers at the University of Notre Dame lent expertise in ionic liquid synthesis and characterization, and researchers at the National Energy Technology Laboratory incorporated candidate ionic liquids into supports and evaluated the resulting materials for membrane performance. Initial results have been very promising with carbon dioxide permeabilities as high as 950 barrers and significant improvements in carbon dioxide/hydrogen selectivity over conventional polymers at 37C and at elevated temperatures. Results include a comparison of the performance of several ionic liquids and a number of supports as well as a discussion of innovative fabrication techniques currently under development.
Date: April 1, 2007
Creator: Luebke, D.R.; Ilconich, J.B.; Myers, C.R. & Pennline, H.W.
Partner: UNT Libraries Government Documents Department

EXAMINATION OF THE PCICE METHOD IN THE NEARLY INCOMPRESSIBLE, AS WELL AS STRICTLY INCOMPRESSIBLE, LIMITS

Description: The conservative-form, pressure-based PCICE numerical method (Martineau and Berry, 2004) (Berry, 2006), recently developed for computing transient fluid flows of all speeds from very low to very high (with strong shocks), is simplified and generalized. Though the method automatically treats a continuous transition of compressibility, three distinct, limiting compressibility regimes are formally defined for purposes of discussion and comparison with traditional methods – the strictly incompressible limit, the nearly incompressible limit, and the f ully compressible limit. The PCICE method’s behavior is examined in each limiting regime. In the strictly incompressible limit the PCICE algorithm reduces to the traditional MAC-type method with velocity divergence driving the pressure Poisson equation. In the nearly incompressible limit the PCICE algorithm is found to reduce to a generalization of traditional incompressible methods, i.e. to one in which not only the velocity divergence effect, but also the density gradient effect is included as a driving function in the pressure Poisson equation. This nearly incompressible regime has received little attention, and it appears that in the past, strictly incompressible methods may have been conveniently applied to flows in this regime at the expense of ignoring a potentially important coupling mechanism. This could be significant in many important flows; for example, in natural convection flows resulting from high heat flux. In the f ully compressible limit or regime, the algorithm is found to reduce to an expression equivalent to density-based methods for high-speed flow.
Date: April 1, 2007
Creator: Berry, Ray A. & Martineau, Richard C.
Partner: UNT Libraries Government Documents Department