In bundles

Uranium oxide [1344-57-6] from mills is converted into uranium hexafluoride [7783-81-5] FJF, for use in gaseous diffusion isotope separation plants (see Diffusion separation methods). The wastes from these operations are only slightly radioactive. Both uranium-235 and uranium-238 have long half-Hves, 7.08 x 10 and 4.46 x 10 yr, respectively. Uranium enriched to around 3 wt % is shipped to a reactor fuel fabrication plant (see Nuclear REACTORS, NUCLEAR FUEL reserves). There conversion to uranium dioxide is foUowed by peUet formation, sintering, and placement in tubes to form fuel rods. The rods are put in bundles to form fuel assembHes. Despite active recycling (qv), some low activity wastes are produced. 

Externally cast membranes are first formed on the iaside of paper, polyester, or polyolefin tubes. These ate then iaserted iato reusable porous stainless-steel support tubes inside diameters ate ca 12 mm. The tubes ate generally shrouded in bundles to aid in permeate collection. 

In some regions of the samples the tubes are found to be closely packed in bundles[20]. Fig. 5 shows a 200 A broad bundle of tubes. Its total length is 2000 A, as determined from a larger scale image. The diameters of the individual tubes range from 20-40 A. They are perfectly aligned and closely packed over the whole length of the bundle. 

As Figure 25.8 shows, the glucose units of cellulose are turned with respect to each other. The overall shape of the chain, however, is close to linear. Consequently, neighboring chains can pack together in bundles where networks of hydrogen bonds stabilize the structure and impart strength to cellulose fibers. 

Figure 10-59. Determination of equal flow areas in bundle cross-flow and baffle window shell-side performance. (Used by permission Engineering Data Book Section II, 1959. Wolverine Tube, Inc.)...

W = flowrate, Ib/hr, condensate Do = outside diameter of tubes, ft Nj = total number of tubes in bundle used for condensation... 

N = number of tubes in bundle Bog = baffle cut area, expressed as fraction, representing opening as percent of shell cross-section area. 

Tong, L. S., 1967b, Heat Transfer in Water-Cooled Nuclear Reactors, Nuclear Eng. Design (5 301. (3) Tong, L. S., 1968a, An Evaluation of the Departure from Nucleate Boiling in Bundles of Reactor Fuel Rods, Nuclear Sci. Eng. 33 7-15. (5)... 

A number of systems which in polymer literature are normally referred to as mesophases are obtained under kinetic control. Examples are the smectic phase of isotactic polypropylene [18,19], mesomorphic syndiotac-tic polypropylene [20-22], mesomorphic PET [23,24], and other instances where intermediate degrees of order result after quenching polymers from the melt to temperatures often close to Tg. In these cases disorder is plausibly more static than in bundles close to T0 and these phases usually crystallize upon heating to an appropriate temperature in the stable crystal phases. 

Although mice with mutations in the myosin-6, -7a, and 15a genes are deaf, these isozymes apparently mediate essential hair-cell functions besides adaptation. Myosin-7a may play an important role in bundle integrity, as mice and fish with no functional myosin-7a protein have highly disheveled bundles. 

From these considerations there evolved the concept of "primary valence chains" in cellulose, held together in bundles, or micelles (crystallites) by secondary forces, as propounded by Meyer and Mark (5). This view was then extended to encompass other high polymers as well. It should be noted however, that Freudenberg had already proposed a chain structure for cellulose, based on degradation experiments (6). If the micelles were to... 

Carbon nanotubes are hollow carbon cylinders with hemispherical endcaps of less than 1 nm to a few nanometres in diameter and several microns in length. The aspect ratios are of the order of 1000 and more. The elementary nanotubes agglomerate in bundles or ropes that are difficult to disperse. 

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