Process enrichment, case

The practices within UCC-ND production facilities ai e to explain to both-, groups the DOs and DON Ts of their, respective jobs. In the case of the operators—those directly involved in processing enriched uranium—criticality safety limits and controls are fully explained. 

For the case of separating a binary mixture, the following conventions are used. The concentrations of the streams are specified by the mol fraction of the desired component. The purpose of the separation process is usually to obtain one component of the mixture in an enriched form. If both components are desired, the choice of the desired component is an arbitrary one. The upflowing stream from the separation stage is the one in which the desired component is enriched, and by virtue of this convention, a is defined as a quantity the value of which is greater than unity. However, for the processes considered here, a exceeds unity by only a very small fraction, and the relationship between the concentrations leaving the stage can be written, without appreciable error, in the form... 

Figure 7 is a schematic representation of a section of a cascade. The feed stream to a stage consists of the depleted stream from the stage above and the enriched stream from the stage below. This mixture is first compressed and then cooled so that it enters the diffusion chamber at some predetermined optimum temperature and pressure. In the case of uranium isotope separation the process gas is uranium hexafluoride [7783-81-5] UF. Within the diffusion chamber the gas flows along a porous membrane or diffusion barrier. Approximately one-half of the gas passes through the barrier into a region... 

Pratt, T. H., Electrostatic Ignition in Enriched Oxygen Atmospheres A Case History, Process Safety Prog., V. 12, No. 4, 1993, p. 203. 

We have previously assumed that the principle diagenetic process is attributable to exchange or interaction of (depleted) browser apatite values with (enriched) sedimentary matrix values (Lee-Thorp and van der Merwe 1987). Another possibility is ionic or isotopic exchange with soil CO2 however in most cases soil CO2 values will be closely related to matrix carbonate values. If the former is the case, one would expect enriched grazer values (near 0%o)... 

The rate of y -alumina island formation essentially depends on the nature of the electrolyte used. If outwards migrating (in the terms of Xu et al.102) anions, such as tungstates and molybdates, are used in the anodization process, y- alumina seed crystals are surrounded by pure alumina and crystallization occurs easily. In the case of inwards migrating anions (e.g., citrates, phosphates, tartrates), the oxide material surrounding the y-nuclei is enriched... 

To test if dilution of the products of CNO burning may explain the difference in abundance pattern with evolved giants and a possible excess in 12 C visible in N-rich stars (see left panel of Fig. 4), we use simple models in the plane [C/N] vs [O/N] (right panel of Fig. 4). Starting from the approximate composition of N-poor stars, the trend for different fractions of gas processed in the complete CNO-cycle (solid line) reproduces fairly well the data, albeit it predict too low C abundances for N-rich dwarfs. Pollution from RGB stars with composition N-rich from very deep mixing (complete CNO and Na enrichment involved, dotted line) reproduces also rather well the data, apart for N-rich dwarfs. On the other hand, the N-poor case, typical of the chemical composition of field RGB stars, is a very poor match (dashed line). Moreover, in this case, the model would predict C-poor, Na-poor stars, whereas no one is observed among over 40 dwarfs/subgiants in the 3 clusters. 

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