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Spontaneous balloon popping - Page 4

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You might be thinking, "This is all very interesting but why should I care? This seems like just some silly demo." Well, it turns out the difference in the ability of different molecules to diffuse through a membrane has many practical industrial applications.

One industrial application appears in the electricity generation and distribution industry. Companies in this industry use SF6 as a gaseous dielectric material to prevent electrical arcs between high voltage electrical components. However, just like the simulation we looked at, air seeps into the vessels containing SF6 and reduces its ability to act as a dielectric. Companies want to keep the SF6 as pure as possible, so they need a way to filter out the air and return purified SF6 to the places where it's used. This can be done using membranes with holes of a carefully chosen and uniform size, much like holes in the membrane in the simulation. A class of membranes known as carbon molecular sieve membranes can be used in this type of application.

Another industrial application is in enriching uranium for use in nuclear power plants. Naturally occurring uranium consists of only about 0.7% 235U, which is the isotope necessary for carrying out fission reactions. However, for use in many common nuclear power plants, uranium must be enriched to contain 3% to 5% U. Historically, the enrichment process involved passing uranium hexafluoride (UF6) through a succession of membranes. The UF6 molecules containing 235U diffused through these membranes slightly more quickly than those containing 238U, so after many passes through the membranes, the remaining UF6 gas is enriched in 235U. Metallic uranium is then made from the 235U-enriched gas and finds its way into commercial nuclear reactors.

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   Page Last Updated: 04.11.2011