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http://www.upi.com/print.cfm?StoryID=20020920-044456-2907r Analysis: Uranium processing difficult By Scott R. Burnell UPI Science News >From the Science & Technology Desk Published 9/20/2002 7:45 PM Transforming uranium ores into fuel for nuclear power plants or the core of atomic bombs is an extensive process requiring a careful combination of chemistry and mechanical precision, a factor that should be considered in the current situation with Iraq. Uranium is a not-uncommon common element in the Earth's crust. It falls 48th on the list of abundance, placing it a little more than halfway down the list of the 92 naturally-occurring elements. It is far more prevalent than silver, for example, according to the U.S. Department of Energy. As it sits in the ground, uranium is made up of three isotopes, differentiated by the number of neutrons in each atom's nucleus. Nearly all naturally occurring uranium -- 99.3 percent -- is U-238. Most of the remaining seven-tenths of a percent is U-235, with U-234 comprising just a trace, the DOE says. The key factor in uranium's use in nuclear applications is its instability. Although U-238 is relatively stable, U-235 can be split apart into lighter elements. This process, called nuclear fission, can release huge amounts of energy -- either slowly within a reactor or nearly instantly in a bomb. Raw uranium ore contains combinations of uranium and oxygen, as well as many other elements that basically prevent fission from occurring in any usable fashion. The chemical mix also prevents uranium from being separated into its isotopes easily. The first step requires milling the ore to yield "yellow cake," a substance consisting of uranium oxides that gets its name from its resemblance to cooked cake mix. In order to isolate the U-235, uranium compounds must be stripped of their oxygen. This requires a series of chemical reactions involving acids, hydrogen and ammonium hydroxide that replace the oxygen with fluorine. The result is uranium hexafluoride, an easily-transported, water-soluble solid with a relatively low boiling point. UF6 still retains about the normal ratio of U-238 to U-235. The hexafluoride must undergo enrichment to boost its percentage of U-235. Standard methods include gaseous diffusion and gas centrifuge, the latter being quicker, cheaper and the center of controversy in Iraq's case. Either way, however, increasing amounts of the heavier U-238 are left behind with each enrichment cycle, raising the percentage of desired U-235. The question of whether or not Iraq is at work on a nuclear device is active because two shipments of high-grade aluminum tubes bound for Iraq have been intercepted in the past 14 months. The tubes are components associated with the enrichment process, although experts remain divided over whether the shipments were centrifuge parts or meant for somewhat less-threatening uses such as artillery rocket tubes. If the parts were destined for a centrifuge, the discovery still means Iraqi scientists would need an extended period to produce usable amounts of weapons-grade material. Starting at the "natural" level of seven-tenths of a percent, uranium is not considered even nuclear power plant fuel until it reaches about 3-to-5 percent U-235. Officials do not use the label "highly enriched" until material attains 20 percent U-235. Theoretically, it is possible to create a nuclear weapon with such material, but even higher enrichment levels are thought necessary for the simplest devices Iraq is thought to desire. Copyright C 2002 United Press International --------------------------- ANTI-NATO INFORMATION LIST ==^================================================================ This email was sent to: [email protected] EASY UNSUBSCRIBE click here: http://topica.com/u/?a84x2u.bacIlu Or send an email to: [EMAIL PROTECTED] T O P I C A -- Register now to manage your mail! http://www.topica.com/partner/tag02/register ==^================================================================
