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| [[Category:Done 2017-07-01]]
| | #REDIRECT [[Gas centrifuge for uranium enrichment]] |
| [[File:gcc.jpg|300px|thumb|right|Figure 1. Cascade of centrifuges used to produce enriched uranium in Piketon Ohio, USA.<ref>Wikimedia Commons. (October 28, 2016). ''Gas Centrifuge Cascade'' [Online]. Available: https://commons.wikimedia.org/wiki/File:Gas_centrifuge_cascade.jpg#/media/File:Gas_centrifuge_cascade.jpg</ref> It's hard to tell from this picture but each of these centrifuges are ~12 meters tall, conventional centrifuges today are ~5 meters tall.]]
| | [[Category: Done 2019-09-05]] |
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| [[Uranium]] that is found in the Earth's crust is made up of 99.289% <sup>238</sup>U and 0.711% <sup>235</sup>U, which are two [[isotope]]s of uranium. In order to use uranium in [[nuclear power plant]]s, uranium [[ore]] must be [[Uranium mining|mined]], milled and then enriched to a higher percentage of <sup>235</sup>U. <onlyinclude>Today, the '''Gas Centrifuge''' (a type of [[centrifuge]] is the main way we go about enriching uranium for nuclear fuel fabrication.</onlyinclude> In World War II, centrifuging was the first process considered for the [[uranium enrichment|enrichment of uranium]]. It was brought to the pilot plant stage before being abandoned for [[gaseous diffusion]].<ref name="r1">John R. Lamarsh, Anthony J. Baratta. (October 31, 2016). ''Introduction to Nuclear Engineering''. Third Edition. Upper Saddle River, NJ, U.S.A:Prentice Hall, 2001.</ref> This centrifuge method for the enrichment of uranium is a sophisticated version of the common method used for many years in biology and medicine for fractionating blood and other biological specimens.<ref name="r1"/>
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| ==Methodology==
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| [[File:Gas_centrifuge_nrc.png|300px|thumb|right|Figure 2. Cross sectional diagram of a single gas centrifuge.<ref>Wikimedia Commons. (October 31, 2016). ''Gas Centrifuge nrc'' [Online]. Available: https://commons.wikimedia.org/wiki/File:Gas_centrifuge_nrc.png</ref>]] | |
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| [[Gas]] centrifugation, like all uranium enrichment processes, utilizes the difference in mass between the <sup>235</sup>U isotope and the <sup>238</sup>U isotope. Because <sup>238</sup>U possesses three more [[neutron]]s in its [[nucleus]] compared to <sup>235</sup>U, it has a higher [[mass]]. In gas centrifugation, the gas that is needing to be separated is pumped into the [[rotor]]. This is where the mass differential between the two isotopes is taken advantage of. The rotor spins at very high speeds, essentially creating a strong gravitational field.<ref name="r1"/> As seen in figure 2, the heavier gas gets pulled to the outside regions of the rotor, whereas the lighter gas stays towards the centre, each being siphoned off by a collection scoop. The amount of separation between the two isotopes depends mostly on the mass difference. The greater the difference in masses, the greater the amount of separation that is achieved. However, separation also greatly depends on the length of the rotor, and its speed of rotation.<ref name="r1"/> Because the mass difference between <sup>235</sup>U and <sup>238</sup>U is so small, a [[Cascade process|cascade]] is required to achieve significant amounts of separation.
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| The rotor is electromagnetically driven and is contained within an evacuated chamber (the casing). The [[Uranium hexafluoride|UF<sub>6</sub>]] gas is fed into the rotor at the axis of rotation, and the enriched and depleted gasses are withdrawn from the bottom and top of the rotor.<ref name="r1"/> As seen in figure 2, depicted by the arrows, an axial countercurrent is applied to the gas by means of a [[temperature gradient]] between the ends of the rotor, depicted by the shaded areas.<ref name="r1"/> The axial countercurrent just means that the gas within the rotor circulates from top to bottom, as shown by the arrows. As the gas moves downward near the rotor axis, the <sup>238</sup>UF<sub>6</sub> [[Diffusion|diffuses]] towards the outer wall. Consequently, the gas arriving at the upper scoop is slightly depleted in <sup>235</sup>UF<sub>6</sub>, and the gas reaching the lower scoop is slightly enriched in <sup>235</sup>UF<sub>6</sub>.<ref name="r1"/>
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| The gas centrifuge method is more economical than the [[gaseous diffusion]] method due to the fact that it requires 96% less electric power than a gaseous diffusion plant of the same [[Separative work unit|separative work]] capacity.<ref name="r1"/> For example, a gaseous diffusion plant of 10 million SWU/yr requires 2700 [[watt|MW]] of electrical capacity, where as the same equivalent plant using centrifuges requires 109 MW of electricity.<ref name="r1"/>
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| ==References==
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| {{reflist}}
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