No description available.

A high power pulsed CO_2 laser was used to induce reactions in gas mixtures containing either N_2F_4 or SF_6. The rate of laser induced dissociation of N_2F_4 to NF_2 was as much as 1000 times faster than the thermal rate, and the rate law was of lower order than the thermal, bimolecular rate law. Explosion threshold and induction time data were obtained for butene stabilized mixtures of N_2F_4 and H_2. HF laser gain was observed during the first few microseconds of CO_2 laser pulse, but it was strongly quenched by the explosion. The laser driven reaction of SF_6 with H_2 also exhibited HF laser gain at early times and laser energy threshold for reaction. All of the laser induced reactions studied occurred at rates that were faster than the rates of thermal reaction. This accelerated reaction rate was attributed to nonthermal vibrational excitation of the reactants. A computer model of the SF_6-H_2 electrical discharge chemical laser was employed to gain a better understanding of the fundamental processes that occur in this laser. Good agreement with experimental results were obtained, and several suggestions for further study were made.

No description available.

Filter holders and continuous air monitors (CAMs) are used extensively in the nuclear industry. It is important to minimize leakage in these devices and in recognition of this consideration, a limit on leakage for sampling systems is specified in ANSI/HPS N13.1-1999; however the protocol given in the standard is really germane to measurement of significant leakage, e.g., several percent of the sampling flow rate. In the present study, a technique for quantifying leakage was developed and that approach was used to measure the sealing integrity of a CAM and two kinds of filter holders. The methodology involves use of sulfur hexafluoride as a tracer gas with the device being tested operated under dynamic flow conditions. The leak rates in these devices were determined in the pressure range from 2.49 kPa (10 In. H2O) vacuum to 2.49 kPa (10 In. H2O) pressure at a typical flow rate of 56.6 L/min (2 cfm). For the two filter holders, the leak rates were less than 0.007% of the nominal flow rate. The leak rate in the CAM was less than 0.2% of the nominal flow rate. These values are well within the limit prescribed in the ANSI standard, which is 5% of the nominal flow rate. Therefore the limit listed in the ANSI standard should be reconsidered as lower values can be achieved, and the methodology presented herein can be used to quantify lower leakage values in sample collectors and analyzers. A theoretical analysis was also done to determine the nature of flow through the leaks and the amount of flow contribution by the different possible mechanisms of flow through leaks.

Filter holders and continuous air monitors (CAMs) are used extensively in the nuclear industry. It is important to minimize leakage in these devices and in recognition of this consideration, a limit on leakage for sampling systems is specified in ANSI/HPS N13.1-1999; however the protocol given in the standard is really germane to measurement of significant leakage, e.g., several percent of the sampling flow rate. In the present study, a technique for quantifying leakage was developed and that approach was used to measure the sealing integrity of a CAM and two kinds of filter holders. The methodology involves use of sulfur hexafluoride as a tracer gas with the device being tested operated under dynamic flow conditions. The leak rates in these devices were determined in the pressure range from 2.49 kPa (10 In. H2O) vacuum to 2.49 kPa (10 In. H2O) pressure at a typical flow rate of 56.6 L/min (2 cfm). For the two filter holders, the leak rates were less than 0.007% of the nominal flow rate. The leak rate in the CAM was less than 0.2% of the nominal flow rate. These values are well within the limit prescribed in the ANSI standard, which is 5% of the nominal flow rate. Therefore the limit listed in the ANSI standard should be reconsidered as lower values can be achieved, and the methodology presented herein can be used to quantify lower leakage values in sample collectors and analyzers. A theoretical analysis was also done to determine the nature of flow through the leaks and the amount of flow contribution by the different possible mechanisms of flow through leaks.

Mémoire (M.Sc.)- Université du Québec à Chicoutimi, 1975. / "Thèse présentée dans le cadre du programme UQ d'études avancées en énergie pour l'obtention du grade de la maîtrise es science (énergie)". CaQCU Document électronique également accessible en format PDF. CaQCU

Metal encapsulation with compressed sulphur hexafluoride gas insulation has reduced the size of power substations and improved their reliability. Due to the superior insulating properties of this gas, its application in Gas Insulated Transmission lines (GITL) and Gas Insulated Substations (GIS) is increasing. Such systems invariably require solid support spacers for supporting high voltage conductors and for compartmentalizing sections of the systems. It has been found that, although the dielectric strength of sulphur hexafluoride is high compared to other gases, in the presence of a solid spacer, the dielectric integrity of the system is impaired. For DC GIS and GITL, free of any particulate contamination, anomalous flashover during a polarity reversal of the applied voltage has been attributed to charge accumulation on the spacer surface. The present work examines the effect of switching impulse voltages on the charge accumulation on support spacers in sulphur hexafluoride gas and the effect of AC precharging on impulse flashover. The charge accumulation on the spacer has been measured using a capacitive probe. A three-dimensional surface charge simulation technique has been developed to convert the probe potential measurements to an equivalent charge distribution. Electric field variation on the spacer surface due to this computed charge can be then obtained with this program. The results indicate that spacers acquire charges even under impulse voltage application in non-uniform field gaps. These charges affect the prebreakdown phenomenon and the breakdown behavior of spacer gaps. Under AC voltages, spacers in uniform fields do not acquire charges as has been reported by previous investigators. Under non-uniform field conditions however, AC precharging of spacers does affect the impulse flashover. The variation however, seems to fall within the statistical scatter of pure impulse flashover. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The scope of supercritical fluid chromatography continues to enlarge. The use of open tublar and packed columns, nearly universal detectors and the introduction of new mobile phases make it more important. In this work sulfur hexafluoride is evaluated as a mobile phase for supercritical fluid chromatography. The separation of a model aromatic hydrocarbon mixture using different packed columns and operational parameters with UV as a detector is presented. The chromatographic properties of supercritical sulfur hexafluoride and supercritical carbon dioxide are compared under corresponding chromatographic parameters. / Master of Science

O hexafluoreto de enxofre (SF6) não figura como um dos gases de efeito estufa com as maiores concentrações no planeta Terra, no entanto, é um gás com um potencial de aquecimento global extremamente grande. Portanto, uma quantidade relativamente pequena pode ter um impacto importante nas mudanças climáticas do globo. Ele é um gás antropogênico, suas emissões são provenientes, principalmente, na distribuição de energia elétrica; é o gás preferido da indústria para interrupção de corrente elétrica e como isolamento de segurança na transmissão e distribuição de eletricidade. Ele é utilizado em disjuntores e equipamentos de alta tensão e na indústria de fundição de magnésio. Este estudo foi desenvolvido com o objetivo de elucidar se existe uma contribuição da Bacia Amazônica, e costa Norte e Nordeste brasileiras nas emissões deste gás, além de mostrar um amplo banco de dados de suas concentrações ao longo do tempo, com início das medições deste o ano 2000. A quantificação do SF6 foi realizada por meio da coleta do ar atmosférico utilizando aviões de pequeno porte que descreveram um perfil vertical em quatro locais, estrategicamente posicionados na Bacia Amazônica, e utilizando sistemas semiautomáticos de coleta de ar em 17 ou 12 altitudes diferentes, juntamente com coletas em 3 locais nas costas Norte e Nordeste brasileiras, com armazenamento das amostras em frascos de vidro. Para a comparação da concentração com estações globais, foram utilizadas as concentrações medidas pela NOAA na Ilha de Ascension e Barbados. Não foi encontrado um caráter emissor da Amazônia e da costa brasileira. Os resultados de uma maneira geral mostram a ocorrência de um crescimento nas concentrações médias obtidas em todos os locais de amostragem com o passar dos anos, acompanhando o crescimento mundial. / Sulfur hexafluoride (SF6) is not one of the greenhouse gases with the highest concentrations on Earth, but it is an extremely potent gas regarding global warming potential. Therefore, a relatively small amount can have a serious impact on global climate change. It is an anthropogenic gas, its emissions are mainly from the distribution of electricity, it is the industry\'s preferred gas for current interruption and as a safety isolation in the transmission and distribution of electricity. It is used in circuit breakers and high voltage equipment, and in the magnesium smelting industry. This study was developed, with the objective of elucidating if there is a contribution of the Amazon Basin, and the North and Northeast Brazilian coasts. In addition, to show a large database of its concentration over time, with the beginning of the measurements since the year 2000. The quantification of SF6 was performed through the sampling of atmospheric air using small airplanes that described a vertical profile in four strategically positioned in the Amazon Basin and using semiautomatic air sampling systems at 17 or 12 different elevations, together with collections at 3 sites on the Brazilian North and Northeast coast, with storage of the samples in glass flasks. The concentrations measured by NOAA in the Ascension Island and Barbados were used as a comparison to global concentrations. No source behavior from the Amazon and the Brazilian coast was found. The results generally show a growth in mean concentrations obtained at all sampling sites over the years, following the same enhancement observed globally.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on September 24, 2009). Thesis advisor: Dr. Scott Kovaleski. Includes bibliographical references.