Results 1 - 10 of 204754
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[en] After ether extraction was scaled up to plant status, solvent extraction grew rapidly, intensively, and extensively. This paper recounts developments at the ORNL in three fields: Fuel Reprocessing, Uranium Production, and Transplutonium Element Recovery. Fuel Reprocessing: In the late 1940's, soon after TBP was discovered to be an extractant, the Purex process was developed to recover, decontaminate, and separate Pu and U (from nitric acid solutions of spent reactor fuels) without the need of added salting agents. Uranium Production: Around 1950, the ORNL Raw Materials Section launched an intensive search for reagents that could extract uranium from sulfuric acid leach liquors. This was accomplished with di(2-ethylhexyl)phosphoric acid (HDEHP) and a suite of high-molecular-weight alkylamines. The resulting Dapex and Amex processes eventually dominated domestic uranium production, spread world-wide, and provided bases for innovative processes in other fields. Transplutonium Element Recovery: Tramex and Talspeak processes accomplish separation of the trivalent actinides from the similar lanthanides. Tramex (1961; amine extraction from concentrated lithium chloride) has been used in the ORNL Transuranium processing Plant (TRU) since 1966. Talspeak (1964; HDEHP extraction from carboxylic acid + aminopolyacetate complexer) has wider potential because it is less corrosive, and it is being extensively studied for separating americium and curium from fuel reprocessing wastes
[en] 'Full text:' Technologies for the production of synthesis gas (H2 + CO), a precursor to hydrogen, from a variety of fossil fuels are well known in industrial applications at relatively large scale. These include Steam Reforming (SR), Auto-Thermal Reforming (ATR) and Partial Oxidation (POX). A particular technology is selected based on the feed type and the desired products. Steam reforming is a mature technology, and is most prevalent for hydrogen production because of its high efficiency. However, at the smaller scale, the capital cost becomes a more significant factor, and a substantial reduction in this cost is necessary to meet the overall H2 gas cost targets, such as that stated by DOE ($1.50/kg). In developing small-scale H2 technologies, often, incremental improvements are incorporated. While useful, these are not adequate for the desired cost reduction. Also, for effective cost reduction, the whole system, including production, purification and associated equipment needs to be evaluated; cost reduction in just one of the units is not sufficient. This paper provides a critical assessment of the existing as well as novel technology options, specifically targeted at small scale H2 production. The technology options are evaluated to clearly point out which may or may not work and why. (author)
[en] Talmesi mine is located in Anarak mineral area in center of Iran and 25 Kilometers distance of north-west from this location. Meskani mine is located in 7 Kilometers west of it. Aforesaid mine has been fully in 1347 after several frequent working and non-working periods. While excavating these mines in the past, damps of minerals have been created in some parts of this region, according to which, the results obtained from mineral processing studies of the excavated minerals. The fundamental studies, confirmed the necessity of mixing different damps and the subsequent processing of resulted sample. Considering the importance of copper element (having grade of approximately %1.20) than other elements, the most emphasis put on the study of this element. The mineralogy studies revealed that the major minerals of copper sulphices include chalcocite, covelline, bornite and chalcopyrite (less than others) and copper mineral oxides comprise of malachite, azurite and cuprite, although copper is natively available as well. Among the gangues; quartz, calcite, dolomite, plagio feldspars, chlorite and fero oxides (less than others) could be introduced. Regarding the difference in special gravity between ores and gunges, the possibility of utilizing gravity methods for separation of these minerals seemed to be logical, but considering the degree of libration in copper minerals (which was determined as %80 in 50-75 microne) and the results of accomplished experiments by shaking table for coarse size and slime table for fine size grains, using the gravity methods was not totally successful. More studies were proceeded by floatation method of copper minerals, because of existing clay and oxide minerals, a desliming phase before floatation was considered to be inecessary. The effective factors of floatation such as optimum time of reduction, Ph, the collector type and quantity, etc. Were all checked and optimized. The basic concentrate could be produced with the degree of 9.37 and relative recovery of %72 as the best condition. The grade increase after several cleaning stages is considerable (%36.64 of copper) and recovery resultant (%62) is appropriate as well. Generally, the other major elements such as nickel, uranium, arsenic and cobalt, has been transformed along with copper to concentrate phase which necessitates the secondary separation activities (specially for uranium as the radioactivate element)
[en] Neural Networks (NNs) are simplified models of the central nervous systems and function as parallel data processing systems. Their peculiar characteristics make them attractive for many tasks, like image processing, which are difficult to handle through conventional techniques. In this project a simple neural network, trained using the backpropagation algorithm with momentum, has been used for compressing 8-bit, gray-scale images. The basic data is to use a 2-layer network with single hidden layer such that the number of neurons in the hidden layer are less than the number of neurons in the input layer. The output of hidden layer is the compressed image which can be used for transmission or storage. The network is then applied to compress new images with reasonable performance. Different issues regarding training and architecture have also been examined. In particular, three normalization functions are used to transform the input data into the range [0,1] or [-1,1], and the result are compared. The effect of number of hidden neurons and the size of training image have also been investigated. (author)
[en] The radiological characterization of contaminated elements (walls, grounds, objects) from nuclear facilities often suffers from too few measurements. In order to determine risk prediction bounds on the level of contamination, some classic statistical methods may therefore be unsuitable, as they rely upon strong assumptions (e.g., that the underlying distribution is Gaussian) which cannot be verified. Considering that a set of measurements or their average value come from a Gaussian distribution can sometimes lead to erroneous conclusions, possibly not sufficiently conservative. This paper presents several alternative statistical approaches which are based on much weaker hypotheses than the Gaussian one, which result from general probabilistic inequalities and order-statistic based formulas. Given a data sample, these inequalities make it possible to derive prediction intervals for a random variable which can be directly interpreted as probabilistic risk bounds. For the sake of validation, they are first applied to simulated data generated from several known theoretical distributions. Then, the proposed methods are applied to two data sets obtained from real radiological contamination measurements. (authors)
[en] Solvent extraction techniques have been used in the uranium nuclear fuel cycle in three main areas; concentration of uranium from ore leach liquor, purification of ore concentrates and fuel reprocessing. Solvent extraction has been extended to the removal of transuranic elements from active waste liquor, the recovery of uranium from natural sources and the recovery of noble metals from active waste liquor. Schemes are presented for solvent extraction of uranium using the Amex or Dapex process; spent fuel reprocessing and the Purex process. Recent and future developments of the techniques are outlined. (UK)
[en] Aiming at the assistant decision-making system’s bottleneck of processing the operational plan data and information, this paper starts from the analysis of the problem of traditional expression and the technical advantage of ontology, and then it defines the elements of the operational plan ontology model and determines the basis of construction. Later, it builds up a semi-knowledge-level operational plan ontology model. Finally, it probes into the operational plan expression based on the operational plan ontology model and the usage of the application software. Thus, this paper has the theoretical significance and application value in the improvement of interconnection and interoperability of the operational plan among assistant decision-making systems. (paper)
[en] Job processing and data transfer are the main computing activities on the WLCG infrastructure. Reliable monitoring of the job processing on the WLCG scope is a complicated task due to the complexity of the infrastructure itself and the diversity of the currently used job submission methods. The paper will describe current status and the new strategy for the job monitoring on the WLCG scope, covering primary information sources, job status changes publishing, transport mechanism and visualization.
[en] Over the past decade there has been a significant advance in flotation circuit optimisation through performance benchmarking using metallurgical modelling and steady-state computer simulation. This benchmarking includes traditional measures, such as grade and recovery, as well as new flotation measures, such as ore floatability, bubble surface area flux and froth recovery. To further this optimisation, Outotec has released its HSC Chemistry software with simulation modules. The flotation model developed by the AMIRA P9 Project, of which Outotec is a sponsor, is regarded by industry as the most suitable flotation model to use for circuit optimisation. This model incorporates ore floatability with flotation cell pulp and froth parameters, residence time, entrainment and water recovery. Outotec's HSC Sim enables you to simulate mineral processes in different levels, from comminution circuits with sizes and no composition, through to flotation processes with minerals by size by floatability components, to full processes with true particles with MLA data.