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Thermodynamic and nonstoichiometric behavior of the GdBa{sub 2}Cu{sub 3}O{sub x} system.

Description: Electromotive force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made on the GdBa{sub 2}Cu{sub 3}O{sub x} system in the temperature range {approximately}400-600 C by means of an oxygen titration technique with an yttria-stabilized zirconia electrolyte. Equations for the variation of oxygen partial pressure with composition and temperature have been derived from our EMF measurements. The shape of the 400 C isotherms as a function of oxygen stoichiometry for the Gd and Nd cuprate systems suggests the presence of miscibility gaps at values of x that are higher than those in the YBa{sub 2}Cu{sub 3}O{sub x} system. For a given oxygen stoichiometry, oxygen partial pressures above Gd-123 and Nd-123 cuprate systems are higher (above x = 6.5) than that for the Y-123 system. A thermodynamic assessment and intercomparison of our partial pressure measurements with the results of related measurements will be presented.
Date: September 29, 1998
Creator: Tetenbaum, M.
Partner: UNT Libraries Government Documents Department

The effect of pressure on annular flow pressure drop in a small pipe

Description: New experimental data was obtained for pressure drop and entrainment for annular up-flow in a vertical pipe. The 9.5 mm. pipe has an L/D ratio of 440 to insure fully developed annular flow. The pressure ranged from 140 kPa to 660 kPa. Therefore the density ratio was varied by a factor of four approximately. This allows the investigation of the effect of pressure on the interfacial shear models. Gas superficial velocities between 25 and 126 m/s were tested. This extends the range of previous data to higher gas velocities. The data were compared with well known models for interfacial shear that represent the state of the art. Good results were obtained when the model by Asali, Hanratty and Andreussi was modified for the effect of pressure. Furthermore an equivalent model was obtained based on the mixing length theory for rough pipes. It correlates the equivalent roughness to the film thickness.
Date: September 1, 1996
Creator: de Bertodano, M.A.L.; Beus, S.G. & Shi, Jian-Feng
Partner: UNT Libraries Government Documents Department

Qualification of a Method to Calculate the Irrecoverable Pressure Loss in High Reynolds Number Piping Systems

Description: High Reynolds number test data has recently been reported for both single and multiple piping elbow design configurations at earlier ASME Fluid Engineering Division conferences. The data of these studies ranged up to a Reynolds number of 42 x 10[sup]6 which is significantly greater than that used to establish design correlations before the data was available. Many of the accepted design correlations, based on the lower Reynolds number data, date back as much as fifty years. The new data shows that these earlier correlations are extremely conservative for high Reynolds number applications. Based on the recent high Reynolds number information a new recommended method has been developed for calculating irrecoverable pressure loses in piping systems for design considerations such as establishing pump sizing requirements. This paper describes the recommended design approach and additional testing that has been performed as part of the qualification of the method. This qualification testing determined the irrecoverable pressure loss of a piping configuration that would typify a limiting piping section in a complicated piping network, i.e., multiple, tightly coupled, out-of-plane elbows in series under high Reynolds number flow conditions. The overall pressure loss measurements were then compared to predictions, which used the new methodology to assure that conservative estimates for the pressure loss (of the type used for pump sizing) were obtained. The recommended design methodology, the qualification testing and the comparison between the predictions and the test data are presented. A major conclusion of this study is that the recommended method for calculating irrecoverable pressure loss in piping systems is conservative yet significantly lower than predicted by early design correlations that were based on the extrapolation of low Reynolds number test data.
Date: September 1, 2002
Creator: Sigg, K. C. & Coffield, R. D.
Partner: UNT Libraries Government Documents Department

Oak Ridge National Laboratory Embrittlement Data Base (EDB) and Dosimetry Evaluation (DE) program

Description: The objective of this program is to develop, maintain, and upgrade computerized data bases, calculational procedures, and standards relating to reactor pressure vessel fluence spectra determinations and embrittlement assessments. As part of this program, the information from radiation embrittlement research on nuclear reactor pressure vessel steels and from power reactor surveillance reports is maintained in a data base published on a periodic basis. The Embrittlement Data Base (EDB) effort consists of verifying the quality of the EDB, providing user-friendly software to access and process the data, and exploring and assessing embrittlement prediction models. The Dosimetry Evaluation effort consists of maintaining and upgrading validated neutron and gamma radiation transport procedures, maintaining cross-section libraries with the latest evaluated nuclear data, and maintaining and updating validated dosimetry procedures and data bases. The information available from this program provides data for assisting the Office of Nuclear Reactor Regulation, with support from the Office of Nuclear Regulatory Research, to effectively monitor current procedures and data bases used by vendors, utilities, and service laboratories in the pressure vessel irradiation surveillance program.
Date: September 1, 1996
Creator: Pace, J. V., III; Remec, I.; Wang, J. A. & White, J. E.
Partner: UNT Libraries Government Documents Department

H-mode pedestal characteristics in ITER shape discharges on DIII-D

Description: Characteristics of the H-mode pedestal are studied in Type 1 ELM discharges with ITER cross-sectional shape and aspect ratio. The scaling of the width of the edge step gradient region, {delta}, which is most consistent with the data is with the normalized edge pressure, ({beta}{sub POL}{sup PED}){sup 0.4}. Fits of {delta} to a function of temperature, such as {rho}{sub POL}, are ruled out in divertor pumping experiments. The edge pressure gradient is found to scale as would be expected from infinite n ballooning mode theory; however, the value of the pressure gradient exceeds the calculated first stable limit by more than a factor of 2 in some discharges. This high edge pressure gradient is consistent with access to the second stable regime for ideal ballooning for surfaces near the edge. In lower q discharges, including discharges at the ITER value of q, edge second stability requires significant edge current density. Transport simulations give edge bootstrap current of sufficient magnitude to open second stable access in these discharges. Ideal kink analysis using current density profiles including edge bootstrap current indicate that before the ELM these discharges may be unstable to low n, edge localized modes.
Date: September 1, 1998
Creator: Osborne, T.H.; Burrell, K.H. & Groebner, R.J.
Partner: UNT Libraries Government Documents Department

The role of gamma rays and freely-migrating defects in reactor pressure vessel embrittlement

Description: Gamma ray effects are often neglected when evaluating reactor pressure vessel (RPV) embrittlement. However, recent analyses indicate that in newer style light water reactors, gamma damage can be a substantial fraction of the total displacement damage experienced by the (RPV); ignoring this damage will lead to errors in embrittlement predictions. Furthermore, gamma rays may be more efficient than fast neutrons at producing freely-migrating defects and as such can impact certain embrittlement mechanisms more effectively than fast neutrons. Consideration of these gamma effects are therefore essential for a more complete understanding of radiation embrittlement.
Date: September 1, 1996
Creator: Alexander, D.E. & Rehn, L.E.
Partner: UNT Libraries Government Documents Department

Carrier localization in gallium nitride

Description: In wide bandgap GaN, a large number of interesting and important scientific questions remain to be answered. For example, the large free electron concentration reaching 10{sup 19} to 10{sup 20} cm{sup - 3} in nominally undoped material are ascribed to intrinsic defects because no chemical impurity has been found at such high concentrations. According to theoretical models, a nitrogen vacancy acts as a donor but its formation energy is very large in n-type materials, making this suggestion controversial. We have investigated the nature of this yet unidentified donor at large hydrostatic pressure. Results from infrared reflection and Raman scattering indicate strong evidence for localization of free carriers by large pressures. The carrier density is drastically decreased by two orders of magnitude between 20 and 30 GPa. Several techniques provide independent evidence for results in earlier reports and present the first quantitative analysis. A possible interpretation of this effect in terms of the resonant donor level is presented.
Date: September 1, 1996
Creator: Wetzel, C.; Walukiewicz, W. & Haller, E.E.
Partner: UNT Libraries Government Documents Department

A novel carbon fiber based material and separation technology

Description: Our novel carbon fiber based adsorbent material shows preferential uptake of CO[sub 2] over other gases. The material has a unique combination of properties, which include a large micropore volume, a large BET surface area, and electrical conductivity. These properties have been exploited to effect the separation of CO[sub 2] from a model gas (CH[sub 4]). Enhanced desorption is achieved using an electrical current passed through the material at low voltage. The manufacture, characterization, and CO[sub 2] adsorption behavior of the materials is reported here, along with our novel electrical swing separation technology.
Date: September 1, 1996
Creator: Burchell, T.D. & Judkins, R.R.
Partner: UNT Libraries Government Documents Department

Megabar liner experiments on Pegasus II

Description: Using pulsed power to implode a liner onto a target can produce high shock pressures for many interesting application experiments. With a Pegasus II facility in Los Alamos, a detailed theoretical analysis has indicated that the highest attainable pressure is around 2 Mbar for a best designed aluminum liner. Recently, an interesting composite liner design has been proposed which can boost the shock pressure performance by a factor 4 over the aluminum liner. This liner design was adopted in the first megabar (Megabar-1) liner experiment carried out on Pegasus last year to verify the design concept and to compare the effect of Rayleigh-Taylor instabilities on liner integrity with the code simulations. We present briefly the physical considerations to explain why the composite liner provides the best shock pressure performance. The theoretical modeling and performance of Megabar-1 liner are discussed. Also presented are the first experimental results and the liner design modification for our next experiment.
Date: September 1, 1997
Creator: Lee, H.; Bartsch, R.R. & Bowers, R.L.
Partner: UNT Libraries Government Documents Department

Composite liner design to maximize the shock pressure beyond megabars

Description: Among the solid liners made of a single material which are imploded onto a target under the same driving condition, the aluminum liner produces the highest shock pressure. The authors propose the composite liner design which can increase the shock pressure several times over the best performance obtainable from an aluminum liner. They have also developed a general formulation to optimize the composite liner design for any driving current, and derived a set of very useful scaling relations. Finally, the authors present some 1-D simulations of the optimal composite liners to be fielded at Pegasus and Procyon in the upcoming megabar experiments.
Date: September 1, 1996
Creator: Lee, H.
Partner: UNT Libraries Government Documents Department

Test container design/fabrication/function for the Waste Isolation Pilot Plant gas generation experiment glovebox

Description: The gas generation experiments (GGE) are being conducted at Argonne National Laboratory-West (ANL0W) with contact handled transuranic (CH-TRU) waste in support of the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico. The purpose of the GGE is to determine the different quantities and types of gases that would be produced and the gas-generation rates that would develop if brine were introduced to CH-TRU waste under post-closure WIPP disposal room conditions. The experiment requires that a prescribed matrix of CH-TRU waste be placed in a 7.5 liter test container. After loaded with the CH-TRU waste, brine and inoculum mixtures (consisting of salt and microbes indigenous to the Carlsbad, New Mexico region) are added to the waste. The test will run for an anticipated time period of three to five years. The test container itself is an ASME rated pressure vessel constructed from Hastelloy C276 to eliminate corrosion that might contaminate the experimental results. The test container is required to maintain a maximum 10% head space with a maximum working pressure of 17.25 MPa (2,500 psia). The test container is designed to provide a gas sample of the head space without the removal of brine. Assembly of the test container lid and process valves is performed inside an inert atmosphere glovebox. Glovebox mockup activities were utilized from the beginning of the design phase to ensure the test container and associated process valves were designed for remote handling. In addition, test container processes (including brine addition, sparging, leak detection, and test container pressurization) are conducted inside the glovebox.
Date: September 1, 1997
Creator: Knight, C.J.; Russell, N.E.; Benjamin, W.W.; Rosenberg, K.E. & Michelbacher, J.A.
Partner: UNT Libraries Government Documents Department

SCC evaluation of candidate container alloys by DCB method

Description: The authors use a solid mechanics approach to investigate hydride formation and cracking in zirconium-niobium alloys used in the pressure tubes of CANDU nuclear reactors. In this approach, the forming hydride is assumed to be purely elastic and its volume dilation is accommodated by elasto-plastic deformation of the surrounding matrix material. The energetics of the hydride formation is revisited and the terminal solid solubility of hydrogen in solution is defined on the basis of the total elasto-plastic work done on the system by the forming hydride and the external loads. Hydrogen diffusion and probabilistic hydride formation coupled with the material deformation are modeled at a blunting crack tip under plane strain loading. A full transient finite element analysis allows for numerical monitoring of the development and expansion of the hydride zone as the externally applied loads increase. Using a Griffith fracture criterion for fracture limitiation, the reduced fracture resistance of the alloy can be predicted and the factors affecting fracture toughness quantified.
Date: September 24, 1999
Creator: Roy, A.K.; Freeman, D.C.; Lum, B.Y. & Spragge, M.K.
Partner: UNT Libraries Government Documents Department

Crack growth monitoring in harsh environments by electrical potential measurements

Description: Electric potential measurement (EPM) technology offers an attractive alternative to conventional nondestructive evaluation (NDE) for monitoring crack growth in harsh environments. Where conventional NDE methods typically require localized human interaction, the EPM technique developed at the Idaho National Engineering and Environmental Laboratory (INEEL) can be operated remotely and automatically. Once a crack-like defect is discovered via conventional means, EPM can be applied to monitor local crack size changes. This is of particular interest in situations where an identified structural defect is not immediately rejectable from a fitness-for-service viewpoint, but due to operational and environmental conditions may grow to an unsafe size with continuing operation. If the location is in a harsh environment where periodic monitoring by normal means is either too costly or not possible, a very expensive repair may be immediately mandated. However, the proposed EPM methodology may offer a unique monitoring capability that would allow for continuing service. INEEL has developed this methodology, supporting equipment, and calibration information to apply EPM in a field environment for just this purpose. Laboratory and pilot scale tests on full-size engineering structures (pressure vessels and piping) have been successfully performed. The technique is applicable to many severe environments because the sensitive equipment (electronics, operators) can be situated in a remote location, with only current and voltage probe electrical leads entering into the harsh environment. Experimental results showing the utility of the methodology are presented, and unique application concepts that have been examined by multiple experiments are discussed.
Date: September 19, 1999
Creator: Lloyd, W. R.; Reuter, W. G. & Weinberg, D. M.
Partner: UNT Libraries Government Documents Department

MHD Instabilities Occurring Near/AT the Transport Barrier, Including Loss of Confinement in H-Modes

Description: In configurations with transport barriers the improved edge and core confinement leads to large pressure gradient and large edge bootstrap current density which often drive magnetohydrodynamic (MHD) instabilities terminating the discharge or reducing the discharge performance. The edge and the core transport barriers deteriorate or are completely lost. In this presentation, recent experimental and theoretical developments concerning MHD instabilities occurring near/at the edge and the core transport barriers are summarized emphasizing the dominant instabilities and the comparison with theory.
Date: September 1, 1999
Creator: Lao, L. L.
Partner: UNT Libraries Government Documents Department

Predictions of structural integrity of steam generator tubes under normal operating, accident, and severe accident conditions

Description: Available models for predicting failure of flawed and unflawed steam generator tubes under normal operating, accident, and severe accident conditions are reviewed. Tests conducted in the past, though limited, tended to show that the earlier flow-stress model for part-through-wall axial cracks overestimated the damaging influence of deep cracks. This observation is confirmed by further tests at high temperatures as well as by finite element analysis. A modified correlation for deep cracks can correct this shortcoming of the model. Recent tests have shown that lateral restraint can significantly increase the failure pressure of tubes with unsymmetrical circumferential cracks. This observation is confirmed by finite element analysis. The rate-independent flow stress models that are successful at low temperatures cannot predict the rate sensitive failure behavior of steam generator tubes at high temperatures. Therefore, a creep rupture model for predicting failure is developed and validated by tests under varying temperature and pressure loading expected during severe accidents.
Date: September 1, 1996
Creator: Majumdar, S.
Partner: UNT Libraries Government Documents Department

Volumetric Properties and Phase Relations of Binary H{sub 2}O-CO{sub 2}-CH{sub 4}-N{sub 2} Mixtures at 300 C and Pressures to 1000 Bars

Description: The volumetric properties and phase relations of binary mixtures of H{sub 2}0, CO{sub 2}, CH{sub 4} and N{sub 2} were determined experimentally at 3OO C, 74.4--999.3 bars, using a custom-built vibrating-tube densimeter. Densities of all single-phase fluids increase steadily with increasing pressure. At a given pressure, CO{sub 2}-rich H{sub 2}O-CO{sub 2} mixtures show a pronounced nonlinear decrease in density with increasing mole fraction CO, in marked contrast to the densities of N{sub 2}-rich H{sub 2}O-N{sub 2} mixtures which are nearly independent of composition. At pressure up to 500 bars, non-aqueous mixtures have much smaller excess molar volumes than gas-rich aqueous mixtures. H{sub 2}O-rich mixtures at pressures ca.86 bars, and CO{sub 2}-poor non-aqueous mixtures at 99.4 bars, exhibit negative excess molar volumes. Excess molar volumes for aqueous mixtures peak at 86 bars, then decrease monotonically with increasing pressure above 86 bars. The H{sub 2}O-CO{sub 2} liquid-vapor field widens continuously from 86 to ca.400 bars, then narrows with increasing pressure, closing at ca.565 bars, in sharp contrast to the H{sub 2}O-N{sub 2} liquid-vapor field, which widens continuously with increasing pressure to at least 1000 bars.
Date: September 12, 1999
Creator: Singh, J.; Blencoe, J.G. & Anovitz, M.
Partner: UNT Libraries Government Documents Department

Study of the phase transition dynamics of the L to H transition

Description: A highly radiating zone (MARFE) just above the divertor X-point has been used to access the marginal transition regime P{sub sep} {approx} P{sub thres} to study the existence of a critical point for the L to H transition. Phase transition models predict that at the critical point, the transition duration increases and the plasma parameters vary continuously between L-mode and H-mode. In these experiments, the L to H transition duration increased 50--100 times over fast transitions. However, the evolution of E{sub r} shear, edge density gradient, H-mode pedestal, and fluctuations is essentially unchanged from that in fast transitions. The only difference is in the speed with which and the degree to which the fluctuation amplitudes are transiently reduced. This difference is understandable in terms of the time scales for fluctuation amplitude reduction ({le} 100 {micro}s) and edge pressure gradient increase (several ms), provided the edge fluctuations are pressure-gradient driven.
Date: September 1, 1997
Creator: Moyer, R. A.; Rhodes, T. L. & Rettig, C. L.
Partner: UNT Libraries Government Documents Department

Energy performance of evacuated glazings in residential buildings

Description: This paper presents the results of a study investigating the energy performance of evacuated glazings or glazings which maintain a vacuum between two panes of glass. Their performance is determined by comparing results to prototype highly insulated superwindows as well as a more conventional. insulating glass unit with a low-E coating and argon gas fill. We used the DOE2.1E energy analysis simulation program to analyze the annual and hourly heating energy use due to the windows of a prototypical single-story house located in Madison, Wisconsin. Cooling energy performance was also investigated. Our results show that for highly insulating windows, the solar heat gain coefficient is as important as the window`s U-factor in determining heating performance for window orientations facing west-south-east. For other orientations in which there is not much direct solar radiation, the window`s U-factor primarily governs performance. The vacuum glazings had lower heating requirements than the superwindows for most window orientations. The conventional low-E window outperformed the superwindows for southwest-south-southeast orientations These performance differences are directly related to the solar heat gain coefficients of the various windows analyzed. The cooling performance of the windows was inversely related to the heating performance. The lower solar heat gain coefficients of the superwindows resulted in the best cooling performance. However, we were able to mitigate the cooling differences of the windows by using an interior shading device that reduced the amount of solar gain at appropriate times.
Date: September 1, 1995
Creator: Sullivan, R.; Beck, F.; arasteh, D. & Selkowitz, S.
Partner: UNT Libraries Government Documents Department

Moessbauer studies of Sr{sub 2}FeO{sub 4} to pressures of 20 GPa

Description: The transport and magnetic properties of the antiferromagnetic semiconductor Sr{sub 2}FeO{sub 4} (Fe{sup 4+}, d{sup 4}) were probed by resistance studies and {sup 57}Fe Moessbauer spectroscopy to 20 GPa using a diamond-anvil cell. The main conclusions of this work are that beyond the onset of the semiconductor-metal transition at {approx}17(1) GPa determined in the resistance studies: (1) the compound is still magnetic and, (2) there is no charge disproportionation of the form: 2Fe{sup 4+} {yields} Fe{sup 3+} + Fe{sup 5+}. The quadrupole splitting ({delta}E{sub Q}) at room temperature (RT) decreases from 0.42 mm/s at ambient pressure to a minimum of 2.2 mm/s at {approx}5.5 GPa. Beyond 5.5 GPa {delta}E{sub Q} at RT increases monotonically reaching 0.5 mm/s at 20 GPa. In the 0-10 GPa pressure range the Neel temperature T{sub N}, is pinned at 60-70 K reaching values of 135(5) K at 19 GPa where the compound is metallic. At 19 GPa and T {much_lt} T{sub N} a simplified magnetic spectrum having an internal magnetic field of {approx}25 T and a substantial quadrupole interaction is obtained.
Date: September 1995
Creator: Hearne, G. R.; Pasternak, M. P. & Rozenberg, G.
Partner: UNT Libraries Government Documents Department

Hydrogen at high pressure and temperatures

Description: Hydrogen at high pressures and temperatures is challenging scientifically and has many real and potential applications. Minimum metallic conductivity of fluid hydrogen is observed at 140 GPa and 2600 K, based on electrical conductivity measurements to 180 GPa (1.8 Mbar), tenfold compression, and 3000 K obtained dynamically with a two-stage light-gas gun. Conditions up to 300 GPa, sixfold compression, and 30,000 K have been achieved in laser-driven Hugoniot experiments. Implications of these results for the interior of Jupiter, inertial confinement fusion, and possible uses of metastable solid hydrogen, if the metallic fluid could be quenched from high pressure, are discussed.
Date: September 30, 1999
Creator: Nellis, W J
Partner: UNT Libraries Government Documents Department

Shock wave measurements

Description: Much of our knowledge of the properties of matter at high pressures, from the static ruby pressure scale to shock compression at Gbar pressures, rests ultimately on the use of shock waves. Simple conservation relations define the initial and final states, leading to absolute measurements. I will describe some methods for measuring the equation of state of materials under shock loading for a variety of methods of shock production, and also describe the basis for other optical methods used widely in shock physics.
Date: September 12, 1995
Creator: Holmes, N.C.
Partner: UNT Libraries Government Documents Department

Selected studies of magnetism at high pressure

Description: Most previous studies of magnetism in various compounds under extreme conditions have been conducted over a wide pressure range at room temperature or over a wide range of cryogenic temperatures at pressures below 20 GPa (200 kbar). We present some of the most recent studies of magnetism over an extended range of temperatures and pressures far beyond 20 GPa, i.e., in regions of pressure-temperature (P-T) where magnetism has been largely unexplored. Recent techniques have permitted investigations of magnetism in selected 3d transition metal compounds in regions of P-T where physical properties may be drastically modified; related effects have often been seen in selected doping studies at ambient pressures.
Date: September 1, 1995
Creator: Hearne, G.R.; Pasternak, M.P. & Taylor, R.D.
Partner: UNT Libraries Government Documents Department

Specific heat of CeRhIn5: Pressure-driven evolution of the ground state from antiferromagnetism to superconductivity

Description: Measurements of the specific heat of antiferromagnetic CeRhIn{sub 5}, to 21 kbar, and for 21 kbar to 70 kOe, show a discontinuous change from an antiferromagnetic ground state below 15 kbar to a superconducting ground state above, and suggest that it is accompanied by a weak thermodynamic first-order transition. Bulk superconductivity appears, apparently with d-wave electron pairing, at the critical pressure, 15 kbar; with further increase in pressure a residual temperature-proportional term in the specific heat disappears.
Date: September 1, 2001
Creator: Fisher, R.A.; Bouquet, F.; Phillips, N.E.; Hundley, M.F.; Pagliuso, P.G.; Sarrao, J.L. et al.
Partner: UNT Libraries Government Documents Department