Editing Isotope separation (section)

===Centrifugal===
[[File:Gas centrifuge cascade.jpg|right|150px|thumb|A cascade of gas centrifuges at a US uranium enrichment plant.]]

[[Centrifugal force|Centrifugal]] schemes rapidly rotate the material allowing the heavier isotopes to go closer to an outer radial wall. This is often done in gaseous form using a [[Zippe-type centrifuge]]. Centrifuging [[plasma (physics)|plasma]] can separate isotopes as well as separating ranges of elements for radioactive waste reduction, nuclear reprocessing, and other purposes. The process is called "plasma mass separation"; the devices are called "plasma mass filter" or "plasma centrifuge" (not to be confused with [[Laboratory centrifuge|medical centrifuges]]).<ref>{{cite journal |last1=Zweben |first1=Stewart J. |last2=Gueroult |first2=Renaud |last3=Fisch |first3=Nathaniel J. |date=12 September 2018 |title=Plasma mass separation |journal=[[Physics of Plasmas]] |volume=25 |issue=9 |page=090901 |doi=10.1063/1.5042845 |bibcode=2018PhPl...25i0901Z |osti=1472074 |s2cid=226888946 |issn=1070-664X|url=https://www.osti.gov/biblio/1472074 }}</ref>

The centrifugal separation of isotopes was first suggested by Aston and Lindemann<ref>{{cite journal |last1=Lindemann |first1=F. A |author-link=Frederick Lindemann, 1st Viscount Cherwell |last2=Aston |first2=F. W. |author-link2=Francis William Aston |title=The possibility of separating isotopes |journal=Philosophical Magazine |series=Series 6 |volume=37 |issue=221 |pages=523–534 |date=1919 |doi=10.1080/14786440508635912 |url=https://zenodo.org/record/1430756}}</ref> in 1919 and the first successful experiments were reported by Beams and Haynes<ref>{{cite journal |last1=Beams |first1=J. W. |last2=Haynes |first2=F. B. |title=The Separation of Isotopes by Centrifuging |journal=Physical Review |publisher=American Physical Society (APS) |volume=50 |issue=5 |date=1936-09-01 |issn=0031-899X |doi=10.1103/physrev.50.491 |pages=491–492|bibcode=1936PhRv...50..491B }}</ref> on isotopes of chlorine in 1936. However attempts to use the technology during the Manhattan Project were unproductive. In modern times it is the main method used throughout the world to enrich uranium and as a result remains a fairly secretive process, hindering a more widespread uptake of the technology. In general a feed of UF<sub>6</sub> gas is connected to a cylinder that is rotated at high speed. Near the outer edge of the cylinder heavier gas molecules containing U-238 collect, while molecules containing U-235 concentrate at the centre and are then fed to another cascade stage.<ref>{{cite journal |last=Whitley |first=Stanley |title=Review of the gas centrifuge until 1962. Part I: Principles of separation physics |journal=Reviews of Modern Physics |publisher=American Physical Society (APS) |volume=56 |issue=1 |date=1984-01-01 |issn=0034-6861 |doi=10.1103/revmodphys.56.41 |pages=41–66|bibcode=1984RvMP...56...41W }}</ref> 

Use of gaseous centrifugal technology to enrich isotopes is desirable as power consumption is greatly reduced when compared to more conventional techniques such as diffusion plants since fewer cascade steps are required to reach similar degrees of separation. As well as requiring less energy to achieve the same separation, far smaller scale plants are possible, making them an economic possibility for a small nation attempting to produce a nuclear weapon. Pakistan is believed to have used this method in developing its nuclear weapons.

[[Vortex tube]]s were used by [[South Africa]] in their [[Helikon vortex separation process]]. The gas is injected tangentially into a chamber with special geometry that further increases its rotation to a very high rate, causing the isotopes to separate.<ref>{{cite web | url=https://inis.iaea.org/search/search.aspx?orig_q=RN:8303315 | title=The Helikon technique for isotope enrichment | date=1976 | last1=p. c. | first1=Haarhoff }}</ref> The method is simple because vortex tubes have no moving parts, but energy intensive, about 50 times greater than gas centrifuges. A similar process, known as ''jet nozzle'' was created in Germany, with a demonstration plant built in Brazil, and they went as far as developing a site to fuel the country's nuclear plants.<ref>{{cite web | url=https://inis.iaea.org/search/search.aspx?orig_q=RN:22063382 | title=Uranium enrichment by jet nozzle separation process in the German-Brazil cooperation program | last1=e. w. | first1=Becker }}</ref>