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Louisiana Gulf Coast seismicity induced by geopressured-geothermal well development

Description: Continuous microseismic monitoring networks have been established around three US Department of Energy geopressured-geothermal design wells in southwestern Louisiana since summer 1980 to assess the effects well development may have on subsidence and growth fault activation. The results obtained from this monitoring have shown several unusual characteristics associated with Gulf Coast seismic activity. The observed activity is classified into two dominant types, one with identifiable body phases and the other with only surface wave signatures. The latter type comprises over 99% of the reported 1000+ microseismic event locations. The problem with the slow-moving surface-wave signature events is that rainfall and weather-associated frontal passages seem closely related to these periods of seismic activity at all three wells. After relatively short periods and low levels of flow testing at the Parcperdue and Sweet Lake prospects, seismic monitoring has shown little credible correlation to inferred growth fault locations during periods of flow testing. Longer periods and higher volumes of flow testing at the Rockefeller Refuge prospect should provide a truer indication of induced seismicity attributable to geopressured-geothermal development. 4 refs., 5 figs.
Date: January 1, 1985
Creator: Stevenson, D.
Partner: UNT Libraries Government Documents Department

Steam generator specification design transients

Description: This LTR documents LOFT Plant operational, upset, and emergency transients, and pressure and temperature conditions as generated by the LOFT Plant Dynamic analysis model of the primary system for use in steam generator specification. The results of this LTR have been supplemented by succeeding efforts as follows: FSAR analysis - (a) loss of load during full power operation, (b) loss of primary pump electrical power, and (c) loss of site power; and LOFT maneuvering analysis - (a) +-10% step change in steam flow, and (b) manual reactor trip. The initial plant conditions considered may differ from this LTR plant conditions. Items are outlined to document in this LTR other analyses which cover the same plant transients. 53 figs., 1 tab.
Date: May 12, 1978
Creator: Stevenson, D.H.
Partner: UNT Libraries Government Documents Department

Fundamental studies of the chemical vapor deposition of diamond

Description: The plasma or thermally enhanced low pressure chemical vapor deposition of diamond films is an exciting development with many challenging fundamental problems. The early stages of nucleation is relevant to the initial growth rate and the perfection and morphology of the deposit. To isolate one of the factors that influence nucleation, we have studied the effect of surface topography on the nucleation process. Our earlier work has shown preferential nucleation on sharp convex features and we have proposed several possible reasons for this behavior, including dangling bonds at the convex features. In our recent work, we have extended our investigation to include a novel patterning of silicon substrates used to pattern silicon solar cells. The results are consistent with our earlier observations that the majority of nucleation events occur on protruding surface features. In an effort to establish whether dangling bonds at the protruding surfaces may be responsible for the selective nucleation, we have evaluated the dangling bond concentration using electron spin resonance. We have carried out deposition under nominally identical surface topography, but with different concentrations of dangling bonds at or near the surface. The results of this study indicate that dangling bonds play a minor role in enhancing nucleation, in contrast to a substantial role played by special surface topographical features. In the course of the past year, we have submitted four manuscripts for publication and have made six presentations.
Date: January 1, 1991
Creator: Stevenson, D.A.
Partner: UNT Libraries Government Documents Department

2001 - 2002 Upper Three Runs Sequence of Earthquakes at the SRS, South Carolina

Description: On October 08, 2001 a small felt earthquake occurred near Upper Three Runs Creek in the north central area of the Savannah River Site, South Carolina. Seven very small aftershocks followed the main event with the last one occurring March 06, 2002. All activity occurred within a small area. Further analysis of collected data indicates a correlation of this low level seismic activity with a small northwest trending structure observed in detailed gravity and magnetic data. Both single event and composite focal mechanisms were derived using local and regional stations. Results indicated predominantly dip-slip motion along a fault striking NNW at 335 degrees and dipping 41 degrees to the southwest. A 3D plot of the eight hypocenters clearly defines a fault plane nearly analogous to that obtained from the focal solutions. The Upper Three Runs series of events is another example of a separate class of earthquakes that occur within the central Piedmont and upper Coastal Plain of South Carolina. The Upper Three Runs sequence of events demonstrates that shallow intersections of structures interpreted from potential field data can be the foci for localized stress concentrations where microearthquake activity can occur. These earthquakes are attributable to small scale faults associated with pockets of relatively high stress concentrations and are generally accompanied by loud noises. Their shallow depth and small aerial extent suggest that these earthquakes are extremely localized and are not attributable to any large scale regional features.
Date: October 16, 2003
Creator: Stevenson, D.A.
Partner: UNT Libraries Government Documents Department

Influence of substrate topography on the nucleation of diamond thin films

Description: Polycrystalline diamond films are of interest because of their unique materials properties. However, depositing films with the desired morphology is hindered by the difficulty in controlling the nucleation process. A popular method of enhancing the nucleation rate and density is to abrade the substrate with diamond powder before deposition. Although effective, this procedure is difficult to analyze since it may leave residual powder, may introduce damage, and may modify the surface topography. In order to separate these effects, we have studied the nucleation on chemically etched silicon substrates. Our results show that the majority of nucleation events occur on protruding surface features.
Date: January 1, 1991
Creator: Dennig, P.A. & Stevenson, D.A.
Partner: UNT Libraries Government Documents Department

Savannah River Site environmental report for 1988

Description: This volume of Savannah River Site Environmental report for 1988 (WSRC-RP-89-59-1) contains the figures and tables referenced in Volume 1. The figures contain graphic illustrations of sample locations and/or data. The tables contain summaries of the following types of data: Federal and State standards and guides applicable to SRS operations; concentrations of radioactivity in environmental media; the quantity of radioactivity released to the environment from SRS operations; offsite radiation dose commitments from SRS operations; measurements of physical properties, chemicals, and metals concentrations in environmental media; and interlaboratory comparison of analytical results.
Date: January 1, 1989
Creator: Cummins, C.L.; Hetrick, C.S.; Stevenson, D.A. (eds.); Davis, H.A.; Martin, D.K. & Todd, J.L.
Partner: UNT Libraries Government Documents Department

Savannah River Site environmental report for 1988

Description: During 1988, as in previous years, Savannah River Site operations had no adverse impact on the general public or the environment. Based on the SRS site-specific code, the maximum radiation dose commitment to a hypothetical individual at the SRS boundary from 1988 SRS atmospheric releases of radioactive materials was 0.46 millirem (mrem) (0.0046 millisievert (mSv)). To obtain the maximum dose, an individual would have had to reside on the SRS boundary at the location of highest dose for 24 hours per day, 365 days per year, consume a maximum amount of foliage and meat which originated from the general vicinity of the plant boundary, and drink a maximum amount of milk from cows grazing at the plant boundary. The average radiation dose commitment from atmospheric releases to the hypothetical individual on the SRS boundary in 1988 was 0.18 mrem (0. 0018 mSv). This person, unlike the maximumly exposed individual, consumes an average amount of foliage, meat, and milk which originated from the foliage and animals living at the plant boundary.
Date: January 1, 1989
Creator: Cummins, C.L.; Hetrick, C.S.; Stevenson, D.A. (eds.); Davis, H.A.; Martin, D.K. & Todd, J.L.
Partner: UNT Libraries Government Documents Department

Progress towards Steady State at Low Aspect Ratio on the National Spherical Torus Experiment (NSTX)

Description: Modifications to the plasma control capabilities and poloidal field coils of the National Spherical Torus Experiment (NSTX) have enabled a significant enhancement in shaping capability which has led to the transient achievement of a record shape factor (S ≡ q95 (Iρ⁄ αΒτ)) of ∼41 (MA m−1 Τ−1) simultaneous with a record plasma elongation of κ ≡ β ⁄ α ∼ 3. This result was obtained using isoflux control and real-time equilibrium reconstruction. Achieving high shape factor together with tolerable divertor loading is an important result for future ST burning plasma experiments as exemplified by studies for future ST reactor concepts, as well as neutron producing devices, which rely on achieving high shape factors in order to achieve steady state operation while maintaining MHD stability. Statistical evidence is presented which demonstrates the expected correlation between increased shaping and improved plasma performance.
Date: November 8, 2007
Creator: D.A. Gates, J. Menard, R. Maingi, S. Kaye, S.A. Sabbagh, S. Diem, J.R.Wilson, M.G. Bell, R.E. Bell, J. Ferron, E.D. Fredrickson, C.E. Kessel, B.P. LeBlanc, F. Levinton, J. Manickam, D. Mueller, R. Raman, T. Stevenson, D. Stutman, G. Taylor, K. Tritz, H. Yu, and the NSTX Research Team
Partner: UNT Libraries Government Documents Department

A multi-model assessment of pollution transport to the Arctic

Description: We examine the response of Arctic gas and aerosol concentrations to perturbations in pollutant emissions from Europe, East and South Asia, and North America using results from a coordinated model intercomparison. These sensitivities to regional emissions (mixing ratio change per unit emission) vary widely across models and species. Intermodel differences are systematic, however, so that the relative importance of different regions is robust. North America contributes the most to Arctic ozone pollution. For aerosols and CO, European emissions dominate at the Arctic surface but East Asian emissions become progressively more important with altitude, and are dominant in the upper troposphere. Sensitivities show strong seasonality: surface sensitivities typically maximize during boreal winter for European and during spring for East Asian and North American emissions. Mid-tropospheric sensitivities, however, nearly always maximize during spring or summer for all regions. Deposition of black carbon (BC) onto Greenland is most sensitive to North American emissions. North America and Europe each contribute {approx}40% of total BC deposition to Greenland, with {approx}20% from East Asia. Elsewhere in the Arctic, both sensitivity and total BC deposition are dominated by European emissions. Model diversity for aerosols is especially large, resulting primarily from differences in aerosol physical and chemical processing (including removal). Comparison of modeled aerosol concentrations with observations indicates problems in the models, and perhaps, interpretation of the measurements. For gas phase pollutants such as CO and O{sub 3}, which are relatively well-simulated, the processes contributing most to uncertainties depend on the source region and altitude examined. Uncertainties in the Arctic surface CO response to emissions perturbations are dominated by emissions for East Asian sources, while uncertainties in transport, emissions, and oxidation are comparable for European and North American sources. At higher levels, model-to-model variations in transport and oxidation are most important. Differences in photochemistry appear to play the ...
Date: March 13, 2008
Creator: Shindell, D T; Chin, M; Dentener, F; Doherty, R M; Faluvegi, G; Fiore, A M et al.
Partner: UNT Libraries Government Documents Department

The Global Atmospheric Environment for the Next Generation

Description: Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using twenty-five state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, whilst the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models, and show a reasonable agreement with surface ozone, wet deposition and NO{sub 2} satellite observations. Large parts of the world are currently exposed to high ozone concentrations, and high depositions of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 {+-} 1.2 ppbv (CLE), and 4.3 {+-} 2.2 ppbv (A2). Only the progressive MFR scenario will reduce ozone by -2.3 {+-} 1.1 ppbv. The CLE and A2 scenarios project further increases in nitrogen critical loads, with particularly large impacts in Asia where nitrogen emissions and deposition are forecast to increase by a factor of 1.4 (CLE) to 2 (A2). Climate change may modify surface ozone by -0.8 {+-} 0.6 ppbv, with larger decreases over sea than over land. This study shows the importance of enforcing current worldwide air quality legislation, and the major benefits of going further. Non-attainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.
Date: December 7, 2005
Creator: Dentener, F; Stevenson, D; Ellingsen, K; van Joije, T; Schultz, M; Amann, M et al.
Partner: UNT Libraries Government Documents Department