22:
233:
lighter molecules towards the central axis. There are two output lines, one for the fraction enriched in the desired isotope (in uranium separation, this is U), and one depleted of that isotope. The output lines take these separations to other centrifuges to continue the centrifugation process. The process begins when the rotor is balanced in three stages. Most of the technical details on gas centrifuges are difficult to obtain because they are shrouded in "nuclear secrecy".
216:
164:. Many of the theorists working with Khan were unsure that either gaseous and enriched uranium would be feasible on time. One scientist recalled: "No one in the world has used the centrifuge method to produce military-grade uranium.... This was not going to work. He was simply wasting time." In spite of skepticism, the program was quickly proven to be feasible. Enrichment via centrifuge has been used in experimental physics, and the method was smuggled to at least
267:
means that the heavier molecules are collected by the wall flow, and the lighter fraction collects at the other end. In a centrifuge with downward wall flow, the heavier molecules collect at the bottom. The outlet scoops are then placed at the ends of the rotor cavity, with the feed mixture injected along the axis of the cavity (ideally, the injection point is at the point where the mixture in the rotor is equal to the feed).
271:
it into the centre of the rotor. The scoops at each end induce opposing currents, so one scoop is protected from the flow by a "baffle": a perforated disc within the rotor which rotates along with the gas—at this end of the rotor, the flow will be outwards, towards the rotor wall. Thus, in a centrifuge with a baffled top scoop, the wall flow is downwards, and heavier molecules are collected at the bottom. Thermally induced
228:, the gas centrifuge uses continuous processing, allowing cascading in which multiple identical processes occur in succession. The gas centrifuge consists of a cylindrical rotor, a casing, an electric motor, and three lines for material to travel. The gas centrifuge is designed with a casing that completely encloses the centrifuge. The cylindrical rotor is located inside the casing, which is
237:
the cylinder. The early units were typically around 2 metres long, but subsequent developments gradually increased the length. The present generation are over 4 metres in length. The bearings are gas-based devices, as mechanical bearings would not survive at the normal operating speeds of these centrifuges.
266:
to enhance the separative effect. A vertical circulating current is set up, with the gas flowing axially along the rotor walls in one direction and a return flow closer to the center of the rotor. The centrifugal separation continues as before (heavier molecules preferentially moving outwards), which
236:
The early gas centrifuges used in the UK used an alloy body wrapped in epoxy-impregnated glass fibre. Dynamic balancing of the assembly was accomplished by adding small traces of epoxy at the locations indicated by the balancing test unit. The motor was usually a pancake type located at the bottom of
232:
of all air to produce a near frictionless rotation when operating. The motor spins the rotor, creating the centrifugal force on the components as they enter the cylindrical rotor. This force acts to separate the molecules of the gas, with heavier molecules moving towards the wall of the rotor and the
240:
A section of centrifuges would be fed with variable-frequency alternating current from an electronic (bulk) inverter, which would slowly ramp them up to the required speed, generally in excess of 50,000 rpm. One precaution was to quickly get past frequencies at which the cylinder was known to suffer
270:
This countercurrent flow can be induced mechanically or thermally, or a combination. In mechanically induced countercurrent flow, the arrangement of the (stationary) scoops and internal rotor structures are used to generate the flow. A scoop interacts with the gas by slowing it, which tends to draw
249:
Later models have steadily increased the rotation speed of the centrifuges, as it is the velocity of the centrifuge wall that has the most effect on the separation efficiency. A feature of the cascade system of centrifuges is that it is possible to increase plant throughput incrementally, by adding
58:
method of U extraction. High degrees of separation of these isotopes relies on using many individual centrifuges arranged in series that achieve successively higher concentrations. This process yields higher concentrations of U while using significantly less energy compared to the gaseous diffusion
1317:
Agreement between the
Government of the United States of America and the Four Governments of the French Republic, the United Kingdom of Great Britain and Northern Ireland, the Kingdom of the Netherlands, and the Federal Republic of Germany Regarding the Establishment, Construction and Operation of
245:
problems. The inverter is a high-frequency unit capable of operating at frequencies around 1 kilohertz. The whole process is normally silent; if a noise is heard coming from a centrifuge, it is a warning of failure (which normally occurs very quickly). The design of the cascade normally allows for
194:
are tall cylinders spinning on a vertical axis. A vertical temperature gradient can be applied to create a convective circulation rising in the center and descending at the periphery of the centrifuge. Such a countercurrent flow can also be stimulated mechanically by the scoops that take out the
189:
rotating at full period at high speed. Concentric gas tubes located on the axis of the rotor are used to introduce feed gas into the rotor and extract the heavier and lighter separated streams. For U production, the heavier stream is the waste stream and the lighter stream is the product stream.
746:
gas is rotated at a high speed. The rotation creates a strong centrifugal force that draws more of the heavier gas molecules (containing the U) toward the wall of the cylinder, while the lighter gas molecules (containing the U) tend to collect closer to the center. The stream that is slightly
258:
The simplest gas centrifuge is the concurrent centrifuge, where separative effect is produced by the centrifugal effects of the rotor's rotation. In these centrifuges, the heavy fraction is collected at the periphery of the rotor and the light fraction from nearer the axis of rotation.
207:. The input of each centrifuge is the product stream of the previous centrifuge. This produces an almost pure light fraction from the product stream of the last centrifuge and an almost pure heavy fraction from the waste stream of the first centrifuge.
219:
Cascade of gas centrifuges used to produce enriched uranium. U.S. gas centrifuge testbed in
Piketon, Ohio, 1984. Each centrifuge is some 40 feet (12 m) tall. (Conventional centrifuges in use today are much smaller, less than 5 metres (16 ft)
591:
202:
In practice, since there are limits to how tall a single centrifuge can be made, several such centrifuges are connected in series. Each centrifuge receives one input line and produces two output lines, corresponding to light and heavy
184:
to separate molecules according to their mass and can be applied to most fluids. The dense (heavier) molecules move towards the wall, and the lighter ones remain close to the center. The centrifuge consists of a rigid body
715:
1246:
45:
accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container. A prominent use of gas centrifuges is for the separation of
246:
the failure of at least one centrifuge unit without compromising the operation of the cascade. The units are normally very reliable, with early models having operated continuously for over 30 years.
141:; Dirac developed the fundamental theory of separation processes that underlies the design and analysis of modern uranium enrichment plants. In the long term, especially with the development of the
324:
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465:
418:
371:
475:
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391:
344:
145:, the gas centrifuge has become a very economical mode of separation, using considerably less energy than other methods and having numerous other advantages.
224:
The gas centrifugation process uses a unique design that allows gas to constantly flow in and out of the centrifuge. Unlike most centrifuges which rely on
1203:
van Wissen, Ralph; Golombok, Michael; Brouwers, J.J.H. (2005). "Separation of carbon dioxide and methane in continuous countercurrent gas centrifuges".
99:, but research was discontinued in 1944 as it was felt that the method would not produce results by the end of the war, and that other means of
1301:
747:
enriched in U is withdrawn and fed into the next higher stage, while the slightly depleted stream is recycled back into the next lower stage.
250:
cascade "blocks" to the existing installation at suitable locations, rather than having to install a completely new line of centrifuges.
635:
989:
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1004:
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195:
enriched and depleted fractions. Diffusion between these opposing flows increases the separation by the principle of
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1340:
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67:
Suggested in 1919, the centrifugal process was first successfully performed in 1934. American scientist
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775:
is used as the gaseous feed medium for the centrifuge cascade. An example of a resulting material is
598:
287:(SWU) is a measure of the amount of work done by the centrifuge and has units of mass (typically
196:
1306:
1318:
Uranium
Enriching Installations Using Gas Centrifuge Technology in the United States of America
148:
Research in the physical performance of centrifuges was carried out by the
Pakistani scientist
112:
72:
25:
Diagram of a gas centrifuge with countercurrent flow, used for separating isotopes of uranium.
586:{\displaystyle W_{\mathrm {SWU} }=P\cdot V\left(x_{p}\right)+T\cdot V(x_{t})-F\cdot V(x_{f})}
191:
142:
111:) had a better chance of success in the short term. This method was successfully used in the
894:
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is expressed in terms of the number of separative work units needed, given by the expression
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396:
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204:
76:
8:
780:
776:
272:
84:
1216:
1171:
1120:
1058:
943:
839:
1157:
859:
792:
768:
739:
423:
376:
329:
34:
847:
1228:
1185:
1000:
908:
851:
153:
149:
104:
88:
55:
42:
1355:
1220:
1175:
1124:
1062:
947:
898:
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627:
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can be created by heating the bottom of the centrifuge and/or cooling the top end.
225:
186:
100:
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80:
21:
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903:
878:
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797:
116:
96:
1302:
Annotated bibliography on the gas centrifuge from the Alsos
Digital Library
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1034:
802:
772:
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181:
165:
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138:
137:
made important theoretical contributions to the centrifugal process during
115:, making the Soviet Union the most effective supplier of enriched uranium.
215:
161:
124:
92:
68:
51:
47:
1103:
Khan, A.Q.; Suleman, M.; Ashraf, M.; Khan, M. Zubair (1 November 1987).
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134:
38:
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1316:
242:
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2003. Institute for
Science and International Security. 10 Oct. 2013
1162:
730:
The separation of uranium requires the material in a gaseous form;
108:
1041:
Khan, Abdul Qadeer; Atta, M. A.; Mirza, J. A. (1 September 1986).
879:"Gas Centrifuge Theory and Development: A Review of U.S. Programs"
710:{\displaystyle V(x)=(1-2x)\cdot \ln \left({\frac {1-x}{x}}\right)}
988:
Brigadier-General (retired) Feroz Hassan Khan (7 November 2012).
756:
999:. Stanford, California: Stanford University Press. p. 151.
1105:"Some Practical Aspects of Balancing an Ultra-Centrifuge Rotor"
229:
725:
1146:"Separative Power of an Optimised Concurrent Gas Centrifuge"
1043:"Flow Induced Vibrations in Gas Tube Assembly of Centrifuge"
253:
156:
for advancing the role of centrifuges in the development of
1040:
983:
981:
979:
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720:
131:
made important contributions to the centrifugal process.
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metal has to be lowered in order to prevent formation of
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54:(U). The gas centrifuge was developed to replace the
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For some uses in nuclear technology, the content of
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1327:
1247:"Engineering Considerations for Gas Centrifuges"
16:Device that performs isotope separation of gases
1284:Global Security.Org. 27 Apr. 2005. 13 Mar. 2008
1143:
742:. Upon entering the centrifuge cylinder, the UF
180:relies on the force resulting from centrifugal
997:Eating grass: the making of the Pakistani bomb
750:
210:
1144:Bogovalov, Sergey; Borman, Vladimir (2016).
726:Separation of uranium-235 from uranium-238
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1161:
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1109:Journal of Nuclear Science and Technology
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1047:Journal of Nuclear Science and Technology
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902:
254:Concurrent and countercurrent centrifuges
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214:
75:developed the process by separating two
20:
1278:Cole-Parmer Technical Lab. 14 Mar. 2008
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721:Practical application of centrifugation
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171:
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1282:"Gas Centrifuge Uranium Enrichment."
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960:
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262:Inducing a countercurrent flow uses
13:
1150:Nuclear Engineering and Technology
1027:Basics of Centrifuge - Cole Parmer
990:"Mastering the Uranium Enrichment"
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488:
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319:{\displaystyle W_{\mathrm {SWU} }}
310:
307:
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14:
1382:
1321:United States Department of State
1295:
1251:Federation of American Scientists
972:Gas Centrifuge Uranium Enrichment
848:10.1038/scientificamerican0878-37
168:by the end of the 20th century.
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1137:
877:Kemp, R. Scott (26 June 2009).
619:{\displaystyle V\left(x\right)}
1211:(16). Elsevier BV: 4397–4407.
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883:Science & Global Security
326:necessary to separate a mass
289:kilogram separative work unit
264:countercurrent multiplication
197:countercurrent multiplication
1205:Chemical Engineering Science
83:. It was one of the initial
41:relies on the principles of
7:
1288:"What is a Gas Centrifuge?"
1276:"Basics of Centrifugation."
1156:(3). Elsevier BV: 719–726.
822:Olander, Donald R. (1978).
786:
751:Separation of zinc isotopes
10:
1387:
211:Gas centrifugation process
109:electromagnetic separation
62:
33:is a device that performs
1312:What is a Gas Centrifuge?
1307:History of the Centrifuge
1225:10.1016/j.ces.2005.03.010
1181:10.1016/j.net.2016.01.024
1082:What is a Gas Centrifuge?
926:Gilinsky, Victor (2010).
904:10.1080/08929880802335816
166:three different countries
87:means pursued during the
808:
152:in the 1970s–80s, using
928:"Remembrances of Dirac"
895:2009S&GS...17....1K
91:, more particularly by
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460:{\displaystyle x_{t}}
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413:{\displaystyle x_{p}}
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366:{\displaystyle x_{f}}
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279:Separative work units
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143:Zippe-type centrifuge
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1361:Pakistani inventions
824:"The Gas Centrifuge"
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285:separative work unit
71:and his team at the
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1217:2005ChEnS..60.4397V
1172:2016NuEnT..48..719B
1121:1987JNST...24..951K
1087:12 May 2003 at the
1059:1986JNST...23..819A
944:2010PhT....63e..59G
840:1978SciAm.239b..37O
828:Scientific American
781:corrosion inhibitor
777:depleted zinc oxide
273:convection currents
172:Centrifugal process
85:isotopic separation
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740:uranium enrichment
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433:{\displaystyle T}
393:of product assay
386:{\displaystyle P}
346:of feed of assay
339:{\displaystyle F}
150:Abdul Qadeer Khan
105:gaseous diffusion
89:Manhattan Project
79:through a vacuum
77:chlorine isotopes
56:gaseous diffusion
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834:(2): 37–43.
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803:Nuclear fuel
779:, used as a
773:Diethyl zinc
754:
729:
630:, defined as
373:into a mass
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1336:Centrifuges
889:(1): 1–19.
125:Klaus Fuchs
117:Franz Simon
93:Harold Urey
69:Jesse Beams
52:uranium-238
48:uranium-235
1330:Categories
1269:References
1256:13 January
1163:1506.00823
440:and assay
178:centrifuge
135:Paul Dirac
39:centrifuge
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1012:8 January
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913:0892-9882
856:0036-8733
692:−
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243:resonance
230:evacuated
205:fractions
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787:See also
1356:Uranium
1213:Bibcode
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187:rotor
1258:2020
1229:ISSN
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1014:2013
1001:ISBN
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