Consumption of ultrapure water (UPW) during semiconductor manufacturing processes is an important topic. A new design of water-dispensing arm employs a small volume of UPW to remove slurry residues inside pad grooves. This innovative water conditioning arm, in contrast to the conventional atomizer and diamond disc, not only reduces UPW consumption by 87% but also reduces scratch defects. The small water volume arm conditioning system injects UPW with diameters at micro levels. Experimental results show that removal amount under continuous polishing conditions is maintained even after 20 runs. The removal amount and profile not only is maintained but improved by over 2% in comparison with the conventional atomizer under no-dressing condition.
Silicon is one of the most significant elements to be applied in industry, it is useful in aluminum production (about 60% of silicon consumption), as an addition to steel and in electronic industry. The present main source of electronic silicon is reduction of silica by carbon at ca. 1900°C, followed by an application of a purification method. Toxic waste formed during these processes is another disadvantage of a standard way of the production of silicon. Therefore, the overall process of silicon production is extremely energy consuming and highly toxic and thereby-environmentally hazardous.
At the present time, one of the main development strategies of nuclear power industry is enhancement of fuel utilization efficiency at NPP during safe and reliable operation. Two main tasks determine the enhancement of the fuel utilization efficiency: -increase the rated power factor of operating NPP power units up to technologically allowable values within the frame of the main project designs provided that the current safety requirements are met and high reliability is ensured; -reduce electric power generation cost and uranium consumption. In order to solve the above tasks, new generation fuel assemblies (FA) are to be developed and used at VVER - 1000 NPP to extend operating lifetime, to increase burnup and to improve operating reliability; thus the fuel cycles to be implemented become safe, cost-effective and flexible as regards NPP requirements. This paper presents the main data on characterization of experimental VVER - 1000 fuel rods which differ in materials and methods of preliminary cladding surface treatment as well as characteristics of fuel pellets after their testing under steady - state conditions at increased power and surface boiling performed in the MIR reactor.
Among the dimensional stone production processes, block splitting into slabs is very important in terms of time, costs and quality of final products. The world’s leading reference equipment for granite block cutting is the multi blade gang saw, in which sawing is the consequence of the combined action of a set of steel blades settled in an oscillating frame and an abrasive slurry containing water, steel shot and lime or bentonite. As the blades enter the block, stone powder is added to the abrasive slurry and as commercial granites include very different rock types, slurry characteristics also depend on the rock nature. Consequently, parameters of the cutting process have great variability. Depending on those parameters, the steel blades and shot are worn out differently during this process having great influence on costs. Due to its complexity, stone cutting mechanisms are still not well understood but compression, abrasion, impact and stone characteristics seem to influence the most. Aiming to help with the understanding of that process and based on previous studies, this work intends to establish correlations between granite petrographic and technological characteristics and steel blades and shot consumption. Laboratorial studies that include petrographic analysis, physical indexes measurement, and abrasion, impact and compression standardized testing of a selected group of stones are being crossed over with steel blades and steel shot consumption measurements in gang saws from several Brazilian processing companies. Although it is a study in progress, preliminary results show a relationship between the characteristics of selected stones and steel blades and shot consumption within the sawing process. The higher the quartz contents of the rock the higher its abrasion resistance, which results in higher consumption of steel shot during sawing. It can be also pointed out that beyond quartz and k-feldspar contents, microfissures seem to have influence on compression strength of the stones and this strength is directly related to the steel blades consumption. This can allow not only a better understanding of slabs production in multi blade gang saws process, but also to improve that process control.
The great amount of resource consumption and the depletion of metal rich primary ores are the main driving forces to develop and utilize the valuable resource hiding in urban mines. Although urban mining possesses several advantages such as lower energy consumption, less cost and easier to develop and less pollution than conventional primary mining, the various wastes generated in the urban mining become a burden for the society because of poor organization production and the implementation of the strict environmental regulations. This paper investigated the environmental problems and the wastes characterization in development and utilization by taking secondary copper as an example. The main pollutants discharged in secondary copper production were exhaust gas containing POPs and metals, waste water of heavy metals and acid water, and the residues of melting and electrolytic plants. The toxic pollutants like heavy metals asked for appropriate dumping and disposal to prevent the damage to the environment.
The Ionic Liquid FEEP (IL-FEEP) thruster is under development at Alta as a variant of the classical cesium FEEP thruster. In this application of the field emission electric thruster concept, the alkali metal propellant is replaced by a ionic liquid. Ionic liquids offer considerable advantages if compared with traditional FEEP propellants such as alkali metals (Cs, Rb) or other liquid metals and alloys (Ga, In, Bi), due to their negligible reactivity with air and water, extremely low vapour tension, low toxicity, and compatibility with a wide range of materials. These aspects lead to significant design simplifications and streamlined ground operations. In comparison with cesium, however, ionic liquids are expected to yield reduced specific impulse and mass efficiency. The study here reported was aimed at the characterization of the thruster plume in terms of composition and velocity of the constituents, with the ultimate goal of getting a reliable estimate of the thruster specific impulse and mass efficiency. To this end, a large number of tests was carried out using a linear slit FEEP emitter fed with the EMI-BF4 ionic liquid. The thruster was fired in positive polarity and negative polarity to check the capability to extract anions and cations alone. Most of the testing was then carried out in alternate polarity mode, in order to avoid electrochemical poisoning of the propellant due to the unbalanced extraction of charged particles. Such operating mode is believed to be the most promising candidate for flight operation, as it would allow to get rid of an external neutralizer to maintain electrical neutrality of the spacecraft. Ion beam composition was investigated with the Time-Of-Flight (TOF) mass spectrometry technique. The measurements show that the emitted beam is mostly composed of monomers (BF4)-, dimers (C6H11BF4N2) (BF4)- and polimers (C6H11BF4N2)n (BF4)-, with 100
In the nuclear power plant (NPP) piping design, major loads considered are pressure, dead weight, seismic and loads due to restraint to thermal expansion. The thermal stresses and seismic stresses are contradictory to each other, in order to reduce the former, piping should be flexible enough to allow gradual thermal expansion and for the later it should be stiff to resist the seismic forces caused by sudden and fast motion. Therefore sometimes it becomes very tedious to include these two contradictory characteristics in same piping using conventional supports. In this condition snubbers are used, which allow the gradual thermal expansion and arrest the fast movement due to earthquake. From the past experiences snubbers have proved to be very costly; need frequent and expensive maintenance, leakage problem in hydraulic snubbers and they also congest the space because of more space requirement for installation. Sometimes it is also observed that the mechanical snubbers lock during normal operation and cause undue thermal stresses in the piping and nozzles. Frequent in-service inspections of snubbers require decontamination and cause man rem consumption. Due to inherent drawbacks and high initial and maintenance cost involved with snubbers, recently a trend has been started to use dampers in place of snubbers. Normally X-shaped plates are chosen as elasto-plastic energy absorbers such that the strain is constant over the height of the device, thus ensuring that yielding occurs simultaneously and uniformly over the full height of the damper. EPDs are based on plastically deforming steel components or layered laminated plates. In the present paper theoretical and experimental characterization of EPDs has been done. The characteristics thus obtained has been used for finite element modelling of EPD supports for codal qualification of Down- Comer piping of Advanced Heavy Water Reactor (AHWR), being designed in India is 920MW(Th.) pressure tube type boiling water reactor using heavy water as moderator and light whater as coolant. A comparison has also been made between the seismic responses of downcomer piping using EPD supports and conventional support.
Despite the strong decrease in industrial and vehicle lead emissions in recent decades, lead-enriched particulate matter (PM) are still locally emitted in the atmosphere, especially by lead-recycling facilities and may represent the main source of lead pollution in the environment. Toxic for living organisms even at low levels, lead can be inhaled and/or ingested as polluted soil and dust particles. Additional routes of exposure include drinking contaminated water and consumption of locally produced vegetables grown in kitchen gardens. Lead contamination of vegetables by atmospheric PM may occurs either through the root-plant transfer (from contaminated soil) or directly by the foliar uptake of PM fallouts. The mechanisms responsible for the foliar uptake are still unclear, and the literature on this topic is very limited compared to soil-root transfer. In that context, our study aims at (i) evaluating the transfer of lead from atmospheric contamination in lettuce, a widely cultivated vegetable and used as a model plant in metal transfer studies and (ii) investigating the mechanisms of foliar lead uptake by monitoring Pb content in leaves and determining its localization and speciation in leaves. In recent papers (1-2), we showed significant Pb levels (335±50 mg Pb kg~(-1) - dry weight) in lettuce leaves after 43 days of exposure to the fallouts of a battery recycling plant emitting Pb-rich particles (333,000 mg Pb/kg particles). We demonstrated that foliar transfer occurs through stomatal openings. In addition, necrotic zones enriched in Pb as well as transformed Pbcontaining particles were observed on leaf surfaces. The present work focuses on the molecular characterization and imaging of these Pb rich areas, in order to better understand the mechanism involved in the foliar transfer of atmospheric Pb rich fallouts at the leaf scale.
Algae have long been known to offer a number of benefits to support long duration human space exploration. Algae contain proteins, essential amino acids, vitamins, and lipids needed for human consumption, and can be produced using waste streams, while consuming carbon dioxide, and producing oxygen. In comparison with higher plants, algae can have higher growth rates, fewer environmental requirements, produce far less "waste" tissue, and are resistant to digestion and/or biodegradation. As an additional benefit,algae produce many compounds (fatty acids, molecular hydrogen, etc.) which are useful as biofuels. On Earth, microalgae survive in many harsh environments including low humidity, and extremes in temperature and pH, and as well as high salinity and solar radiation. Algae can adapt to high and low light intensity while retaining their ability to perform nitrogen fixation and photosynthesis and have been shown to survive in microgravity. Studies have demonstrated that some algae are resistant to the space radiation environment, including solar ultraviolet radiation. It remains to be experimentally demonstrated, however, that an algal-based system could fulfil the requirements for a space-based Bioregenerative Life Support System (BLSS) under comparable spaceflight power, mass, and environmental constraints. Two specific challenges facing algae cultivation in space are that (i) conventional growth platforms require large masses of water, which in turn require a large amount of propulsion fuel, and (ii) most gas exchange mechanisms (predominantly bubbling) are dependent on gravity. To address these challenges, we have constructed a low water biofilm based bioreactor whose operation is enabled by capillary forces. Preliminary characterization of this Surface Adhering BioReactor (SABR) suggests that it can serve as a platform for cultivating algae in space which requires about 10 times less mass than conventional reactors without sacrificing growth rate. Further work is necessary to compare the performance of microalgae-based systems, including SABR, with systems based on higher plants, as well as conventional physicochemical-based systems. Ongoing and future work in our laboratory is therefore directed determining the feasibility of using algae as a component of a BLSS in space.
Pyrite (FeS_2), the most common sulfide mineral in Earth's surface environments, is a strong indicator of reducing conditions in aqueous environments (Descostes et al., 2004). The abundance of pyrite in nature and the important role of pyrite formation in geochemical cycles has spurred numerous experimental investigations addressing formation, mechanisms at low temperatures (< 100°C) and over a broad range of solution chemistries (Rickard and Luther, 2007 and references therein). The principal steps in sedimentary pyrite formation require the consumption of iron compounds to varying degrees through reaction with microbially-formed hydrogen sulfide (Luther 1991). The results presented here are part of an investigation of pyrite formation in organic-rich sediments, including coal. There are several working hypotheses for pyrite formation: a) iron is deposited diagenetically and pyrite formation is biologically driven; b) pyrite is being dissolved and residual iron is adsorbing to the surface; or c) pyrite is formed epigenetically, as iron attached to the coal surface reacts with sulfur compounds via percolating surface water or interactions with groundwater. The interaction of iron with both mineral and organic matter makes characterization of iron partitioning difficult, and thus it is poorly understood in modern and ancient organic-rich sediments. We have developed a sequential extraction allowing detailed information on the speciation of iron in coal. Five sediment iron fractions are characterized (1) surficially bonded Fe; (2) organically bound Fe (Fe_(org)); (3) carbonate-associated Fe, including siderite and ankerite; (4) reducible oxides, including ferrihydrite, lepidocrocite, goethite; (4) silicate Fe; and (5) pyrite Fe. Iron fractions were determined using a combination of pressurized fluid extraction, using EDTA and NMP, as well as leaching on a suite of carmel, lignite, and coal- samples collected from different coal regions within the United States. Preliminary data from a sample of bituminous coal collected from the Clarion Coal seam (Turkey City, PA) suggests that 90% of iron within the coal is bound to the coal surface. Additional samples are being processed and trends will be assessed between samples and coal quality groups. Ultimately, iron distribution within the coal seam has important implications for inferring formation and dissolution conditions. Understanding iron partitioning may assist in optimizing coal processing and combustion while minimizing environmental impacts.