Effect Of Carrier Gas Composition Research Articles

Advances in the understanding of molybdenum effect on iodine and caesium reactivity in condensed phase in the primary circuit in nuclear severe accident conditions

In the case of a severe accident in a Light Water Reactor, the issue of late release of fission products, from the primary circuit surfaces is of particular concern due to the direct impact on the source term. CsI is the main iodine compound present in the primary circuit and can be deposited as particles or condensed species. Its chemistry can be affected by the presence of molybdenum, and can lead to the formation of gaseous iodine. The present work studied chemical reactions on the surfaces involving gaseous iodine release. CsI and MoO3 were used to highlight the effects of carrier gas composition and oxygen partial pressure on the reactions. The results revealed a noticeable effect of the presence of molybdenum on the formation of gaseous iodine, mainly identified as molecular iodine. In addition, the oxygen partial pressure prevailing in the studied conditions was an influential parameter in the reaction.

A Scoping Study of the Chemical Behavior of Cesium Iodide in the Presence of Boron in the Condensed Phase (650°C and 400°C) Under Primary Circuit Conditions

This work is a contribution toward understanding the chemical reactions on the primary circuit surfaces involving gaseous iodine release during a severe nuclear reactor accident. Cesium iodide was used as a nonradioactive precursor material in order to highlight the effects of carrier gas composition (Ar/H2O, Ar/H2O/H2, and Ar/Air), temperature, the initial cesium/iodine (Cs/I) molar ratio by adding cesium hydroxide, and the presence of boron on the molar composition of the deposited iodine compound and on the release of gaseous iodine from the deposit. The results from the experiments involving only cesium iodide as a precursor revealed a slight decomposition of cesium iodide and a release of gaseous iodine. Furthermore, the measured gaseous iodine mass decreased with the addition of hydrogen to the carrier gas at 650°C. At 400°C, the amount of released material (aerosol and gas) was decreased. However, whereas at 650°C the sampled iodine existed mainly as aerosols, the mass concentration recorded from the experiment at 400°C indicated a predominance of gaseous iodine. When the initial Cs/I molar ratio was significantly greater than unity (1.5 < Cs/I < 4.5), the mass of produced gaseous iodine was barely detectable, suggesting a reaction between cesium hydroxide and the gaseous iodine released from cesium iodide decomposition. In the presence of boron, the transport of gaseous iodine was increased as a result of the formation of glassy cesium borate in the evaporation crucible. The presence of steam and its quantity were shown to have an enhancing influence on the cesium borate formation and on the release of gaseous iodine.

Production of ammonia from plasma-catalytic decomposition of urea: Effects of carrier gas composition

Effects of carrier gas composition (N2/air) on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an Al2O3-packed dielectric barrier discharge (DBD) reactor at room temperature. Results show that the presence of O2 in the carrier gas accelerates the conversion of urea but leads to less generation of NH3. The final yield of NH3 in the gas phase decreased from 70.5%, 78.7%, 66.6% and 67.2% to 54.1%, 51.7%, 49.6% and 53.4% for applied voltages of 17, 19, 21 and 23kV, respectively when air was used as the carrier gas instead of N2. From the viewpoint of energy savings, however, air carrier gas is better than N2 due to reduced energy consumption and increased energy efficiency for decomposition of a fixed amount of urea. Carrier gas composition has little influence on the major decomposition pathways of urea under the synergetic effects of plasma and Al2O3 catalyst to give NH3 and CO2 as the main products. Compared to a small amount of N2O formed with N2 as the carrier gas, however, more byproducts including N2O and NO2 in the gas phase and NH4NO3 in solid deposits were produced with air as the carrier gas, probably due to the unproductive consumption of NH3, the possible intermediate HNCO and even urea by the abundant active oxygen species and nitrogen oxides generated in air-DBD plasma.

Effect of carrier gas composition on transferred arc metal nanoparticle synthesis

Metal nanoparticles are used in a great number of applications; an effective and economical production scaling-up is hence desirable. A simple and cost-effective transferred arc process is developed, which produces pure metal (Zn, Cu, and Ag) nanoparticles with high production rates, while allowing fast optimization based on energy efficiency. Different carrier gas compositions, as well as the electrode arrangements and the power input are investigated to improve the production and its efficiency and to understand the arc production behavior. The production rates are determined by a novel process monitoring method, which combines an online microbalance method with a scanning mobility particle sizer for fast production rate and size distribution measurement. Particle characterization is performed via scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction measurements. It is found that the carrier gas composition has the largest impact on the particle production rate and can increase it with orders of magnitude. This appears to be not only a result of the increased heat flux and melt temperature but also of the formation of tiny nitrogen (hydrogen) bubbles in the molten feedstock, which impacts feedstock evaporation significantly in bi-atomic gases. A production rate of sub 200 nm particles from 20 up to 2,500 mg/h has been realized for the different metals. In this production range, specific power consumptions as low as 0.08 kWh/g have been reached.

Can modern infrared analyzers replace gas chromatography to measure anesthetic vapor concentrations?

BackgroundGas chromatography (GC) has often been considered the most accurate method to measure the concentration of inhaled anesthetic vapors. However, infrared (IR) gas analysis has become the clinically preferred monitoring technique because it provides continuous data, is less expensive and more practical, and is readily available. We examined the accuracy of a modern IR analyzer (M-CAiOV compact gas IR analyzer (General Electric, Helsinki, Finland) by comparing its performance with GC.MethodsTo examine linearity, we analyzed 3 different concentrations of 3 different agents in O2: 0.3, 0.7, and 1.2% isoflurane; 0.5, 1, and 2% sevoflurane; and 1, 3, and 6% desflurane. To examine the effect of carrier gas composition, we prepared mixtures of 1% isoflurane, 1 or 2% sevoflurane, or 6% desflurane in 100% O2 (= O2 group); 30%O2+ 70%N2O (= N2O group), 28%O2 + 66%N2O + 5%CO2 (= CO2 group), or air. To examine consistency between analyzers, four different M-CAiOV analyzers were tested.ResultsThe IR analyzer response in O2 is linear over the concentration range studied: IR isoflurane % = -0.0256 + (1.006 * GC %), R = 0.998; IR sevoflurane % = -0.008 + (0.946 * GC %), R = 0.993; and IR desflurane % = 0.256 + (0.919 * GC %), R = 0.998. The deviation from GC calculated as (100*(IR-GC)/GC), in %) ranged from -11 to 11% for the medium and higher concentrations, and from -20 to +20% for the lowest concentrations. No carrier gas effect could be detected. Individual modules differed in their accuracy (p = 0.004), with differences between analyzers mounting up to 12% of the medium and highest concentrations and up to 25% of the lowest agent concentrations.ConclusionM-CAiOV compact gas IR analyzers are well compensated for carrier gas cross-sensitivity and are linear over the range of concentrations studied. IR and GC cannot be used interchangeably, because the deviations between GC and IR mount up to ± 20%, and because individual analyzers differ unpredictably in their performance.

The ADU vaporizing unit: a new vaporizer.

We determined the performance of the vaporizer of the ADU machine (Anesthesia Delivery Unit; Datex-Ohmeda, Helsinki, Finland). The effects of carrier gas composition (oxygen, oxygen/N(2)O mixture, and air) and fresh gas flow (0.2 to 10 L/min) on vaporizer performance were examined with variable concentrations of isoflurane, sevoflurane, and desflurane across the whole range of each vaporizer's output. In addition, the effects of sudden changes in fresh gas flow and carrier gas composition, back pressure, flushing, and tipping were assessed. Vaporizer output depended on fresh gas flow, carrier gas composition, dial settings, and the drug used. Vaporizer output remained within 10% of dial setting with fresh gas flows of 0.3-10 L/min for isoflurane, within 10% of dial setting with fresh gas flows of 0.5-5 L/min for sevoflurane, and within 13% of dial setting with fresh gas flows of 0.5 to 1 L/min for desflurane. Outside these fresh gas flow ranges, output deviated more. The effect of sudden changes in fresh gas flow or carrier gas composition, back pressure, flushing, and tipping was minimal. We conclude that the ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer. The ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer.

The ADU Vaporizing Unit: A New Vaporizer

We determined the performance of the vaporizer of the ADU machine (Anesthesia Delivery Unit; Datex-Ohmeda, Helsinki, Finland). The effects of carrier gas composition (oxygen, oxygen/N2O mixture, and air) and fresh gas flow (0.2 to 10 L/min) on vaporizer performance were examined with variable concentrations of isoflurane, sevoflurane, and desflurane across the whole range of each vaporizer’s output. In addition, the effects of sudden changes in fresh gas flow and carrier gas composition, back pressure, flushing, and tipping were assessed. Vaporizer output depended on fresh gas flow, carrier gas composition, dial settings, and the drug used. Vaporizer output remained within 10% of dial setting with fresh gas flows of 0.3–10 L/min for isoflurane, within 10% of dial setting with fresh gas flows of 0.5–5 L/min for sevoflurane, and within 13% of dial setting with fresh gas flows of 0.5 to 1 L/min for desflurane. Outside these fresh gas flow ranges, output deviated more. The effect of sudden changes in fresh gas flow or carrier gas composition, back pressure, flushing, and tipping was minimal. We conclude that the ADU vaporizer performs well under most clinical conditions. Despite a different design and the use of complex algorithms to improve accuracy, the same physical factors affecting the performance of conventional vaporizers also affect the ADU vaporizer.

The effects of carrier gas composition on the performance of the Tec 6 desflurane vaporizer.

The new Tec 6 desflurane vaporizer is an electrically heated, pressurized, electromechanically coupled dual-circuit blender. We hypothesized that carrier gas viscosity should affect the electromechanical coupling of the fresh gas and vapor circuits, and that desflurane output should vary with different carrier gases. In the first portion of the study, the performance of eight vaporizers was evaluated using a constant dial setting of 10% desflurane with four different carrier gases and three different fresh gas flow rates. In the second portion of the study, the carrier gas flow rate was maintained at 1, 5, or 10 L/min, and vaporizer output was analyzed at all integer dial settings from 1% to 18%. Vaporizer output was highest when oxygen was the carrier gas and lowest when nitrous oxide was the carrier gas. This effect was accentuated at low fresh gas flow rates and correlated with carrier gas viscosity. At a flow rate of 1.0 L/min with a constant dial setting of 10%, the averaged output from vaporizers was 10.3 +/- 0.66, 9.4 +/- 0.58, 8.7 +/- 0.52, and 8.1 +/- 0.44 vol% for 100% oxygen, air, 30% oxygen plus 70% nitrous oxide, and 100% nitrous oxide, respectively. With 100% nitrous oxide as the carrier gas at a flow rate of 1.0 L/min, the vaporizer delivered 2 vol% less than the dial setting at dial settings in excess of 12%. Differences between the analyzed concentration and the dial setting were most pronounced with high concentrations of nitrous oxide at low fresh gas flow rates.

EFFECTS OF CARRIER GAS COMPOSITION ON THE OUTPUT OF SIX ANAESTHETIC VAPORIZERS

The effect of carrier gas composition on the output of six anaesthetic vaporizers was studied using oxygen, nitrous oxide, helium and argon as the carrier gases. Vaporizer output was measured with an MGA 200 mass spectrometer and a Riken refractometer and, in addition, the pressure decrease across each vaporizer was determined simultaneously. A change in carrier gas composition produced both a transient and a steady state change in vaporizer output. The possible reasons for the changes in steady state output are discussed in relation to the construction of each vaporizer. The addition of nitrous oxide to the carrier gas produced changes of clinical significance only when the vaporizers were used at extreme dial settings and flow rates.

A correction for the effect of drying of air samples and its significance to the interpretation of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; measurements

Non-dispersive infrared gas analysers used for the measurement of atmospheric carbon dioxide concentration are influenced by water vapour in the air sample. It has thus become common practice to dry the air prior to analysis. The subsequent measurement must be corrected by multiplying the indicated concentration by (1 + 1.61<em>r</em>)⁻¹, where r is the water vapour mass mixing ratio of the undried air. The correction is of the order 1% near the surface, varying in both space (e.g. with latitude) and time (e.g. day-today and seasonally), and of the same order of magnitude as the measured but uncorrected horizontal, vertical and seasonal CO₂ variations. Thus serious doubt is thrown on previous comparisons of global CO₂ measurements. Ideally each CO₂ analysis of an air sample should be corrected using knowledge of the water vapour concentration of the undried air. For data obtained in the past, appropriate correction may be possible after consideration of the water vapour conditions in the atmosphere at each of the monitoring stations. This should be done by the research personnel involved with each monitoring programme, together with a consideration of the effects of carrier gas composition on the gas analyser(s) employed.

Lubrication of Ball Bearings with Volatile Organic Compounds

A new approach to vapor lubrication describing materials for wide temperature range and long term operation has been established by experiments that use high-speed rolling element bearings as test specimens. Several possibilities for the process of vapor lubrication are projected. In addition the effect of carrier gas composition as well as metal substrate alloying element or cladding component is demonstrated for a variety of volatile organic compounds. The significance of dispersion techniques for the volatile compounds carried by nitrogen gas is shown by experiments conducted for naphthalene.